Immunology and Serology MCQs Chapter 6: Test your knowledge with important immunology and immune system MCQs. These MCQs are also beneficial for competitive exams. Explore more frequently asked questions at Lab Tests Guide.

MCQs:
The study of the immune system, known as immunology, is crucial in diagnosing and treating various medical conditions. Immunology laboratory professionals perform a wide range of tests and analyzes to help healthcare providers make accurate diagnostic and treatment decisions. To excel in this field, laboratory personnel must have a deep understanding of immunology, and mastering multiple choice questions (MCQs) can be an exceptionally effective way to achieve this goal.
Immunology and Serology MCQs 251 to 300
- Same or closely related antigens present in different biological species are known as_____?
- Suquestrated antigens
- Isoantigens
- Haptens
- Heterophile antigens
Answer and Explanation
Answer: Heterophile antigens
Heterophile antigens are molecules found in different species that share some degree of similarity. This similarity can cause the immune system of one species to mistakenly react to the antigens of another species.
The other options are incorrect:
- sequestered antigens: These are antigens hidden within a body’s own cells and not typically exposed to the immune system.
- Isoantigens: These are antigens found on the red blood cells of an individual that are different from another individual of the same species.
- Haptens:These are small molecules that cannot trigger an immune response on their own but can bind to larger carrier molecules and elicit a response.
- Rh incompatibility is which type of hyper sensitivity reaction ?
- Type I
- Type II
- Type III
- Type IV
Answer and Explanation
Answer: Type II
Rh incompatibility is a type II hypersensitivity reaction. This means it involves antibodies (IgG) targeting and destroying Rh-positive red blood cells. The complement system is often activated, leading to cell lysis.
The other options are incorrect:
- Type I: This is also known as immediate hypersensitivity, involving IgE antibodies and mast cells, causing allergic reactions like hay fever or anaphylaxis. (Not relevant to red blood cell destruction)
- Type III: This is immune complex hypersensitivity, where antigen-antibody complexes deposit in tissues and trigger inflammation. (Not specific to red blood cells)
- Type IV: This is delayed-type hypersensitivity, involving T cells and taking longer to develop. It’s seen in reactions like poison ivy rash. (Not involving antibodies directly attacking cells)
- The prototype of Type II hypersensitivity reaction is_____?
- Arthus reaction
- SLE
- Auto immune hemolytic anemia
- Contact dermatitis
Answer and Explanation
Answer: Auto immune hemolytic anemia
Autoimmune hemolytic anemia is a type II hypersensitivity reaction where antibodies mistakenly target a person’s own red blood cells, leading to their destruction. This reaction involves IgG antibodies binding to red blood cells, triggering complement activation or phagocytosis by immune cells.
The other options are incorrect:
- Arthus reaction: This is a type III hypersensitivity involving immune complex deposition in tissues, causing inflammation. (Not directly targeting cells)
- SLE (Systemic Lupus Erythematosus): This is a complex autoimmune disease that can involve various types of hypersensitivity, including type II. However, it isn’t the prototype specifically for type II.
- Contact dermatitis: This is a type IV hypersensitivity reaction mediated by T cells. It typically involves a delayed inflammatory response to allergens contacting the skin. (Not involving antibodies directly attacking cells)
- A woman with infertility receives an ovary transplant from her sister who is an identical Twin. What type of graft it is ?
- Xenograft
- Autograft
- Allograft
- Isograft
Answer and Explanation
Answer: Isograft
An isograft is a transplant of tissue between genetically identical individuals, such as identical twins. Since the donor and recipient share the same genetic makeup, there is minimal risk of rejection by the recipient’s immune system.
The other options are incorrect:
- Xenograft: This refers to a transplant between different species (e.g., pig heart valve to human).
- Autograft: This is a transplant of tissue from one part of the body to another within the same individual.
- Allograft: This is a transplant of tissue between individuals of the same species but with different genetic makeup. Allografts carry a risk of immune rejection.
- Type I hypersensitivity is mediated by which of the following immunoglobulins ?
- IgA
- IgG
- IgM
- IgE
Answer and Explanation
Answer: IgE
Type I hypersensitivity, also known as immediate hypersensitivity, is triggered by the binding of allergens to specific IgE antibodies. These antibodies attach to mast cells and basophils, causing them to release inflammatory mediators like histamine upon re-exposure to the allergen. This leads to the rapid onset of allergic symptoms.
The other options are incorrect:
- IgA: This immunoglobulin is primarily found in mucosal secretions like saliva and tears, protecting against pathogens at these entry points. It’s not typically involved in type I hypersensitivity.
- IgG: This is the most abundant antibody and plays a crucial role in the immune response against various pathogens. However, it’s not the primary mediator in type I hypersensitivity reactions.
- IgM: This is the first antibody produced in a primary immune response and helps in agglutination (clumping) of pathogens. It’s not involved in type I hypersensitivity.
- Active artificial immunization is induced by the administration of all of the following EXCEPT______?
- Bacterial products
- Toxoids
- Vaccines
- Antitoxins
Answer and Explanation
Answer: Antitoxins
Active artificial immunization involves the administration of antigens to stimulate an immune response and generate long-lasting immunity. This is typically achieved through vaccines or toxoids. Antitoxins, on the other hand, provide passive immunity by supplying pre-formed antibodies and do not stimulate the body’s own immune response.
The other options are incorrect:
- Bacterial products: These can include components of bacteria or inactivated forms of bacteria used in vaccines to induce an immune response and provide active immunization.
- Toxoids: These are inactivated toxins from bacteria that are used to induce an immune response without causing disease. Examples include the tetanus and diphtheria vaccines.
- Vaccines: Vaccines contain antigens from pathogens (live attenuated, inactivated, or subunit) that stimulate the immune system to develop immunity. They are a primary method of active artificial immunization.
- Immunity that is conferred to the foetus by transfer of IgG and IgA antibodies is called as______?
- Active acquired immunity
- Passive acquired immunity
- Natural active immunity
- Passive natural immunity
Answer and Explanation
Answer: Passive natural immunity
Passive natural immunity refers to the immunity conferred to a fetus through the transfer of maternal antibodies, specifically IgG and IgA. IgG antibodies cross the placenta, while IgA is transferred through breast milk, providing the newborn with temporary protection against infections.
The other options are incorrect:
- Active acquired immunity: This type of immunity is developed when an individual’s immune system is exposed to an antigen through infection or vaccination, leading to the production of antibodies and memory cells.
- Passive acquired immunity:This involves the transfer of pre-formed antibodies from an immune individual to a non-immune individual through medical interventions, such as administering immunoglobulin therapy, not naturally as with maternal transfer.
- Natural active immunity: This occurs when an individual is exposed to a pathogen naturally (through infection), leading to the
- The protective effects breast milk are known to be associated with______?
- IgM antibodies
- Lysozyme
- Mast cells
- IgA antibodies
Answer and Explanation
Answer: IgA antibodies
The protective effects of breast milk are primarily associated with IgA antibodies. These antibodies play a crucial role in mucosal immunity, protecting the gastrointestinal tract of the infant from pathogens by preventing their attachment and invasion.
The other options are incorrect:
- IgM antibodies: These are the first antibodies produced in a primary immune response but are not prevalent in breast milk.
- Lysozyme: This enzyme is present in breast milk and can break down bacterial cell walls, offering some protection. However, IgA antibodies play a more significant role.
- Mast cells: These immune cells are not found in breast milk. They are present in the body and release inflammatory mediators during allergic reactions.
- IL-1 and TNF a during inflammation are secreted by_______?
- Plasma cells
- Activated macrophages
- Lymphocytes
- Platelet
Answer and Explanation
Answer: Activated macrophages
During inflammation, activated macrophages are key players in the immune response. They become activated by various stimuli like damaged cells or pathogens and release a variety of signaling molecules, including cytokines like IL-1 and TNF-alpha. These cytokines contribute to inflammation by attracting immune cells, promoting fever, and stimulating other immune responses.
The other options are incorrect:
- Plasma cells: These are differentiated B lymphocytes that produce large amounts of antibodies, not cytokines like IL-1 and TNF-alpha.
- Lymphocytes: While lymphocytes play a crucial role in the immune system, not all types directly secrete IL-1 and TNF-alpha during inflammation. Specific T lymphocyte subsets can produce these cytokines, but macrophages are the primary source.
- Platelets: These are involved in blood clotting and don’t secrete cytokines like IL-1 and TNF-alpha.
- Virus infected cell is killed by____?
- Interferons
- Macrophages
- Neutrophils
- Autolysis
Answer and Explanation
Answer: Interferons
Interferons are signaling proteins released by virus-infected cells to alert neighboring cells and induce an antiviral state. They also stimulate the immune system to recognize and destroy virus-infected cells, thus playing a crucial role in the elimination of viruses.
The other options are incorrect:
- Macrophages: Macrophages engulf and digest pathogens but do not directly kill virus-infected cells through apoptosis.
- Neutrophils: Neutrophils are a type of white blood cell involved in phagocytosis and releasing antimicrobial agents. They do not induce apoptosis in virus-infected cells.
- Autolysis: Autolysis refers to the process of self-destruction of cells, typically through activation of enzymes within the cell. While infected cells may undergo apoptosis, autolysis is not the primary mechanism by which virus-infected cells are killed.
- Prozone phenomenon is due to______?
- Disproportionate antigen antibody levels
- Excess antigen
- Excess antibody
- Hyper immune reaction
Answer and Explanation
Answer: Excess antibody
The prozone phenomenon is an immunological quirk that occurs in antigen-antibody reactions when there’s an excess of antibody present. Normally, antibodies bind to antigens to form immune complexes, which can then be visualized in certain tests. However, with too much antibody, these complexes can actually be too large or abundant to be detected, leading to a false negative result.
The other options are incorrect:
- Disproportionate antigen antibody levels: This is a general term encompassing both excess antigen and excess antibody. We need to pinpoint the specific culprit for the prozone phenomenon.
- Excess antigen: In contrast to excess antibody, an excess of antigen can overwhelm the available antibodies, preventing them from efficiently binding and forming detectable complexes. This can lead to a different phenomenon called the high-dose hook effect, but not the prozone phenomenon.
- Hyper immune reaction: This refers to an excessive immune response, not specifically related to the prozone phenomenon, which is a limitation of the test itself due to antibody concentration.
- Most sensitive test for antigen detection is_______?
- Radioimmuno Assay
- ELISA
- Immunoflourescence
- Passive hemaglutination
Answer and Explanation
Answer: ELISA
ELISA is a highly sensitive and versatile technique that can detect a wide range of antigens. It uses a series of steps involving antibodies linked to enzymes to amplify the signal generated by the antigen, allowing for more accurate detection compared to other options listed.
The other options are incorrect:
- Radioimmuno Assay (RIA): While RIA is also a sensitive technique, it involves radioactivity, making it more complex and hazardous compared to ELISA.
- Immunofluorescence: Immunofluorescence can be very sensitive, but it requires specialized equipment and expertise to interpret the results.
- Passive Hemagglutination: This method is less sensitive than ELISA and relies on the clumping of red blood cells, making it less precise for quantitative antigen detection
- Complement binding immunoglobin via the classical pathway is_______?
- IgG & igM
- IgG & IgA
- IgG & IgD
- IgD & IgE
Answer and Explanation
Answer: IgG & igM
In the classical pathway of the complement system, C1q, the first protein in the cascade, binds specifically to the Fc region of IgG and IgM antibodies that are complexed with antigens. This binding triggers a series of reactions that ultimately lead to the elimination of the pathogen.
The other options are incorrect:
- IgG & IgA: IgA does not effectively activate the classical complement pathway due to its Fc region structure.
- IgG & IgD: IgD plays a role in B cell activation but doesn’t bind C1q to activate the classical pathway.
- IgD & IgE: Neither IgD nor IgE effectively activate the classical complement pathway through C1q binding.
- Function of Ig A is_____?
- Acts as a mucosal barrier for infection
- Circulating antibody
- Kills virus infected cells
- Activates macrophages
Answer and Explanation
Answer: Acts as a mucosal barrier for infection
IgA is the predominant antibody class in mucosal secretions like saliva, tears, and breast milk. It helps prevent pathogens from attaching to epithelial cells lining these surfaces and establishing infection. By neutralizing and blocking pathogens, IgA acts as a first line of defense at mucosal surfaces.
The other options are incorrect:
- Circulating antibody: While small amounts of IgA can be found in blood, its concentration is much higher in mucosal secretions where it plays a specialized role.
- Kills virus infected cells: This is a function of cytotoxic T cells, which are immune cells that directly target and eliminate infected cells. Antibodies like IgA do not have this capability.
- Activates macrophages: IgA does not directly activate macrophages. Its primary role is in mucosal immunity, not in activating immune cells like macrophages.
- Antigen combining site of the antibody is______?
- Idiotope
- Paratope
- Epitope
- Hapten
Answer and Explanation
Answer: Paratope
The paratope is the specific region on an antibody molecule that interacts with and binds to a complementary region on an antigen, known as the epitope. This specific binding allows the antibody to neutralize or target the antigen for destruction.
The other options are incorrect:
- Idiotope: An idiotope is a unique antigenic determinant on an antibody molecule that can be recognized by other antibodies. It’s not the region responsible for antigen binding.
- Epitope: The epitope is the complementary region on the antigen that the paratope on the antibody binds to. It’s the target on the antigen, not the binding site on the antibody.
- Hapten: A hapten is a small molecule that can bind to an antibody but cannot trigger an immune response on its own. It may compete with a larger antigen for antibody binding, but it’s not the antigen binding site itself.
- Opsonisation is by_____?
- IgM
- IgE
- IgG
- Both A & C
Answer and Explanation
Answer: IgG
IgG is the most abundant antibody class in the blood and is particularly effective at opsonization. The Fc portion of IgG binds to specific receptors on phagocytes, such as macrophages and neutrophils, which flags the pathogen for engulfment and destruction.
The other options are incorrect:
- IgM: While IgM can activate the complement system, which can contribute to opsonization, it’s not as efficient as IgG in directly binding to phagocytes.
- IgE: IgE is primarily involved in allergic reactions and defense against parasitic worms. It doesn’t play a major role in opsonization for most pathogens.
- Both A & C: IgG is the primary opsonizing antibody, so both A and C wouldn’t be the correct answer.
- The antigen used in Weil Felix test is obtained from______?
- Pseudomonas
- coli
- Proteus
- Staphylococcus
Answer and Explanation
Answer: Proteus
The Weil-Felix test utilizes specific strains of Proteus bacteria (Proteus OX19, OX2, and OXK) because their antigens share similarities with certain Rickettsia species, the bacteria that cause rickettsial diseases. Antibodies developed in response to a Rickettsia infection can cross-react with these Proteus antigens.
The other options are incorrect:
- Pseudomonas: Pseudomonas is a different genus of bacteria not related to Proteus or Rickettsia.
- Escherichia coli (coli): E. coli is another unrelated bacteria commonly found in the intestines.
- Staphylococcus: Staphylococcus is another genus of bacteria not involved in the Weil-Felix test. It lacks the necessary antigenic similarity to Rickettsia.
- Adjuvant given along with antigens are going to_____?
- Increase toxigenicity
- Increase antigenicity
- Reduce the antigenicity
- reduce the toxigenicity
Answer and Explanation
Answer: Increase antigenicity
Adjuvants are added to vaccines alongside antigens (parts of germs that trigger an immune response) to enhance the immune system’s response. This means they help the body recognize the antigen more effectively and develop a stronger immunity.
The other options are incorrect:
- Increase toxigenicity: Toxins are poisonous substances produced by some bacteria. Adjuvants do not make antigens more toxic.
- Reduce the antigenicity: This would defeat the purpose of an adjuvant. Adjuvants are specifically designed to increase the antigenicity (the ability of a substance to trigger an immune response).
- Reduce the toxigenicity: While some vaccines may contain weakened or inactivated toxins, adjuvants themselves don’t directly affect the toxicity of antigens.
- IgG has subclasses______?
- 1
- 2
- 3
- 4
Answer and Explanation
Answer: 4
IgG is the most abundant antibody class in the blood and it’s further divided into four subclasses: IgG1, IgG2, IgG3, and IgG4. Each subclass has slightly different properties and functions within the immune system.
The other options are incorrect:
- 1: IgG has more than just one subclass.
- 2: While significant, 2 isn’t the complete number of subclasses.
- 3: IgG has one more subclass than this option.
- Human immunoglobulins are divided based on_____?
- Functional differences
- Structural differences
- Complemented fixation
- None of the above
Answer and Explanation
Answer: Structural differences
Human immunoglobulins, also known as antibodies, are classified into five main classes (IgG, IgA, IgM, IgD, and IgE) based on variations in the structure of their heavy chains. These structural differences lead to functional differences between the antibody classes. For instance, IgG is good at opsonization (tagging pathogens for destruction), while IgE is involved in allergic reactions.
The other options are incorrect:
- Functional differences: While immunoglobulins do have distinct functions, these functions are a consequence of their structural differences.
- Complement fixation: Complement fixation is a specific function of some antibodies, particularly IgG and IgM, but it’s not the basis for classification.
- None of the above: Structural differences in the heavy chains are the primary way to categorize human immunoglobulins.
- IgG antibodies have a half-life of approximately_____?
- 1 hour
- 1 day
- 1 week
- 1 Month
Answer and Explanation
Answer: 1 Month
The half-life of an antibody refers to the time it takes for the concentration of that antibody in the bloodstream to decrease by half. IgG antibodies, being the most abundant class of antibodies in the blood, have a relatively long half-life compared to other antibody classes. Their half-life is approximately 1 month, which means it takes about that long for the concentration of IgG antibodies to decrease by half.
The other options are incorrect:
- 1 hour: This option is incorrect because the half-life of IgG antibodies is much longer than just 1 hour.
- 1 day: While IgG antibodies have a longer half-life than 1 day, they last much longer in the bloodstream.
- 1 week: IgG antibodies have a longer half-life than just 1 week.
- The distinguishing characteristic of a positive delayed type hypersensitivity skin test is______?
- Erythema
- Necrosis
- Induration
- Vasculitis
Answer and Explanation
Answer: Induration
A positive delayed type hypersensitivity (DTH) skin test results in induration, which is a firm, raised area at the injection site. This induration develops 48-72 hours after the test due to T-cell mediated inflammation.
The other options are incorrect:
- Erythema: Redness at the injection site can occur in both positive and negative DTH tests.
- Necrosis: Tissue death is not a typical reaction in a positive DTH test.
- Vasculitis: Inflammation of blood vessels is not a primary feature of a positive DTH test.
- Type of receptor present on T-cells are_____?
- Ig A
- Ig G
- Prostaglandins
- CD4
Answer and Explanation
Answer: CD4
CD4 is a protein receptor found on the surface of T helper cells, a specific type of T lymphocyte. It plays a crucial role in the immune response by binding to specific molecules on antigen-presenting cells.
The other options are incorrect:
- Ig A & Ig G: These are types of antibodies produced by B cells, not receptors on T cells.
- Prostaglandins: These are signaling molecules involved in various physiological processes, not specific receptors on immune cells.
- In patients with asthma due to an allergic cause the serum levels of which immunoglobulin increase_____?
- IgD
- IgM
- IgA
- IgE
Answer and Explanation
Answer: IgE
In allergic asthma, the immune system overreacts to allergens, leading to increased production of IgE. This immunoglobulin binds to mast cells and basophils, triggering the release of inflammatory mediators that cause asthma symptoms.
The other options are incorrect:
- IgD: IgD plays a minor role in the immune system and isn’t significantly elevated in allergic asthma.
- IgM: IgM is the first antibody produced in response to an infection, not a primary player in allergies.
- IgA: IgA is important for mucosal immunity but isn’t a major factor in allergic asthma.
- Which of the following immunoglobulins has the highest mean serum concentration in humans_____?
- IgA
- IgD
- IgG
- IgM
Answer and Explanation
Answer: IgG
IgG is the most abundant immunoglobulin in human serum, accounting for approximately 80-85% of total immunoglobulins. It provides long-term immunity against various pathogens and toxins.
The other options are incorrect:
- IgA: IgA makes up around 10-15% of serum immunoglobulins and is concentrated in mucosal secretions like saliva and tears.
- IgD: IgD has a very low concentration in serum, typically less than 0.3%. Its exact function remains under investigation.
- IgM: IgM constitutes 5-7% of serum immunoglobulins and is the primary antibody produced during the initial stages of an infection.
- Immunoglobulin crossing placenta is______?
- Ig M
- Ig A
- Ig G
- Ig D
Answer and Explanation
Answer: Ig G
IgG is the only immunoglobulin that can effectively cross the placenta in significant amounts. This transfer provides passive immunity to the developing fetus, protecting them from infections the mother has antibodies against.
The other options are incorrect:
- IgM: IgM is too large to cross the placenta efficiently and therefore does not provide passive immunity to the fetus.
- IgA: While IgA can be found in breast milk, it does not cross the placenta to provide immunity to the fetus.
- IgD: IgD is primarily found on the surface of B cells and is not involved in placental transfer or fetal immunity.
- The key cell types involved in the acquired immunity include all EXCEPT_____?
- B lymphocytes
- Erythrocytes
- T lymphocytes
- Antigen presenting cells (APC
Answer and Explanation
Answer: Erythrocytes
Erythrocytes, or red blood cells, are not involved in acquired immunity. Acquired immunity primarily involves B lymphocytes, T lymphocytes, and antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells.
The other options are incorrect:
- B lymphocytes: These cells mature in the bone marrow and differentiate into plasma cells that produce antibodies specific to antigens.
- T lymphocytes: These cells mature in the thymus and orchestrate various cell-mediated immune responses.
- Antigen Presenting Cells (APCs): These cells (e.g., macrophages, dendritic cells) process antigens and present them to T lymphocytes, initiating the adaptive immune response.
- Complement factor through which common pathway begins_____?
- C3
- C5
- C2
- Protein B
Answer and Explanation
Answer: C3
The complement system has multiple activation pathways, but they all converge at the level of C3. Cleavage of C3 by C3 convertase (formed via different pathways) is the central point where the common pathway begins, leading to a cascade of events that eliminate pathogens.
The other options are incorrect:
- C5: C5 is a downstream component of the common pathway involved in membrane attack complex formation, not the initiation point.
- C2: C2 is a component needed for C3 convertase formation in the classical and lectin pathways, but cleavage of C3 marks the start of the common pathway.
- Protein B: Protein B is a factor specifically involved in the alternative pathway, not the common pathway initiated by C3 cleavage.
- The term epitope refers to_____?
- complete antigen molecule
- Hapten
- Immunogen
- Smallest antigenic determinant
Answer and Explanation
Answer: Smallest antigenic determinant
An epitope is the specific region on an antigen molecule that is recognized and bound by antibodies or T-cell receptors. It’s the smallest part of the antigen that triggers an immune response.
The other options are incorrect:
- Complete antigen molecule: An antigen is the entire molecule recognized by the immune system, and the epitope is a specific part of that molecule.
- Hapten: A hapten is a small molecule that can bind to antibodies but cannot trigger an immune response on its own. It may require attachment to a larger carrier molecule to become immunogenic.
- Immunogen: An immunogen is any molecule capable of inducing an immune response, which can encompass the entire antigen molecule or a fragment containing the epitope.
- Post streptococcal acute glomerulo nephritis is an example of_______?
- Type I hypersensitivity
- Type II hypersensitivity
- Type III hypersensitivity
- Type IV hypersensitivity
Answer and Explanation
Answer: Type III hypersensitivity
Post-streptococcal acute glomerulonephritis is an example of a Type III hypersensitivity reaction, where immune complexes deposit in the glomeruli, leading to inflammation and kidney damage.
The other options are incorrect:
- Type I hypersensitivity (immediate hypersensitivity): This type involves IgE-mediated allergic reactions, not immune complex deposition.
- Type II hypersensitivity (antibody-dependent cellular cytotoxicity): This type involves antibodies directly targeting and damaging host cells, not immune complex formation.
- Type IV hypersensitivity (delayed type hypersensitivity): This type involves T cell-mediated reactions taking 48-72 hours to develop, not involving immediate immune complex effects
- The type of immunoglobulin most commonly increased in multiple myeloma is_____?
- IgG
- IgA
- IgM
- IgD
Answer and Explanation
Answer: IgG
IgG is the most common type of immunoglobulin found elevated in multiple myeloma. Around 70% of patients with multiple myeloma have high levels of IgG protein in their blood.
The other options are incorrect:
- IgA: IgA is the second most common immunoglobulin increased in multiple myeloma, affecting about 20% of patients.
- IgM, IgD: These immunoglobulins are very rarely elevated in multiple myeloma. IgM elevation is more indicative of Waldenstrom’s macroglobulinemia, another plasma cell malignancy.
- The function of IgD is_______?
- Antigen recognition by B cells
- Localization protection in external secretion
- Compliment activation
- Reagin activity
Answer and Explanation
Answer: Antigen recognition by B cells
The primary function of IgD is antigen recognition by B cells. IgD is expressed on the surface of mature B cells along with IgM and serves as a receptor for antigen recognition.
The other options are incorrect:
- Localization protection in external secretion: IgA is the primary immunoglobulin involved in protecting mucosal surfaces.
- Complement activation: IgD is not known to directly activate the complement system.
- Reagin activity: This term is often used in the context of IgE, which is involved in allergic reactions. IgD doesn’t have this specific function.
- Cleavage of IgG molecule by Papin gives rise to:One Fc fragment and two Fab fragments_____?
- One Fc fragment and two Fab fragments
- One Fc fragment and four Fab fragments
- Two Fc fragments and two Fab fragments
- Two Fc fragment and one Fab fragment
Answer and Explanation
Answer: One Fc fragment and two Fab fragments
Papain, a cysteine protease, specifically cleaves the hinge region of IgG molecules. This cleavage separates the antigen-binding Fab fragments (two identical arms) from the Fc fragment (crystallizable fragment) responsible for effector functions.
The other options are incorrect:
- One Fc fragment and four Fab fragments: Papain cleavage yields two Fab fragments, not four.
- Two Fc fragments and two Fab fragments: Papain cleaves within the hinge region, resulting in one Fc fragment, not two.
- Two Fc fragment and one Fab fragment: Similar to the previous option, papain cleavage yields two Fab fragments, not one.
- T cell matures in____?
- Payers patch
- Lymph node
- Thymus
- Busra of Fabricius
Answer and Explanation
Answer: Thymus
T cells, also known as thymocytes, develop and mature in the thymus, a specialized lymphoid organ located in the upper chest area. The thymus plays a crucial role in shaping the T cell repertoire by eliminating self-reactive T cells that could attack the body’s own tissues.
The other options are incorrect:
- Peyer’s Patches: These are lymphoid structures in the small intestine involved in mucosal immunity and B cell activation.
- Lymph Node: Lymph nodes are filter stations for immune cells throughout the body, but they are not the primary site for T cell maturation.
- Bursa of Fabricius: This lymphoid organ is present in birds and plays a role in B cell development. It’s not relevant to T cell maturation in humans.
- CD4 cells recognize the antigens in association with______?
- MHC I
- MHC II
- MHC III
- B-cell receptor
Answer and Explanation
Answer: MHC II
CD4 cells recognize antigens in association with Major Histocompatibility Complex (MHC) class II molecules. MHC class II molecules present exogenous antigens to CD4+ T cells, initiating an immune response.
The other options are incorrect:
- MHC I: MHC class I molecules are primarily associated with antigen presentation to CD8+ T cells (cytotoxic T lymphocytes).
- MHC III: MHC class III molecules are less well-characterized but are not typically involved in classical antigen presentation by T cells.
- B-cell receptor: The B-cell receptor is a protein complex on the surface of B cells that allows them to recognize antigens directly, not requiring MHC presentation.
- IL-1 is produced by______?
- Helper T cells
- Helper B cells
- Monocytes
- Macrophages
Answer and Explanation
Answer: Macrophages
Interleukin-1 (IL-1) is primarily produced by macrophages. It plays a key role in the immune response by stimulating the production of other cytokines, promoting inflammation, and activating lymphocytes.
The other options are incorrect:
- Helper T cells (Th cells): While Th cells can produce other cytokines, IL-1 production is not a major function of these T lymphocyte subsets.
- Helper B cells: Similar to Th cells, B cells are not primary producers of IL-1. Their primary role is antibody production.
- Monocytes: Monocytes are precursors to macrophages and can produce various cytokines, but IL-1 is mainly produced by mature macrophages.
- Grave’s disease is an example of type immunologic response______?
- Type I
- Type II
- Type III
- Type IV
Answer and Explanation
Answer: Type II
Graves’ disease is an autoimmune disorder characterized by the presence of antibodies that mimic the thyroid-stimulating hormone (TSH) and stimulate the thyroid gland to produce excessive thyroid hormones. This falls under Type II hypersensitivity.
The other options are incorrect:
- Type I (immediate hypersensitivity): This type involves IgE-mediated allergic reactions, not antibody-induced stimulation of a healthy tissue.
- Type III (immune complex-mediated hypersensitivity): This type involves immune complexes causing tissue damage, not direct cellular stimulation.
- Type IV (delayed type hypersensitivity): This type involves T cell-mediated reactions taking 48-72 hours to develop, not antibody-driven effects.
- Type IV hypersensitivity reaction is mediated by which of the following_______?
- B-cells
- Active T cells
- NK cells
- Plasma cells
Answer and Explanation
Answer: Active T cells
Type IV hypersensitivity reactions, also known as delayed-type hypersensitivity reactions, are mediated by activated T cells, particularly CD4+ T cells (helper T cells) and CD8+ T cells (cytotoxic T cells).
The other options are incorrect:
- B-cells: B-cells are responsible for antibody production, not directly involved in cell-mediated immunity of type IV hypersensitivity.
- NK cells (Natural Killer cells): While NK cells play a role in immune defense, they are not the primary mediators of type IV hypersensitivity reactions.
- Plasma cells: Plasma cells are terminally differentiated B cells that produce antibodies. They are not directly involved in the initial activation and response seen in type IV hypersensitivity.
- Which of the following are correctly matched ?
- Transfer of antibody from mother to child is through colostrum and acquired passive immunity naturally
- Injection of antibodies (Hepatitis) is artificially acquired passive immunity
- Antigenic stimulus given by vaccine (polio) is artificial active immunity
- All of the above
Answer and Explanation
Answer:All of the above
All the statements are correctly matched:
- Transfer of antibody from mother to child is through colostrum and acquired passive immunity naturally: Colostrum, the first milk produced by mothers after childbirth, is rich in antibodies (IgA) that provide the newborn with temporary immunity until their own immune system matures.
- Injection of antibodies (Hepatitis) is artificially acquired passive immunity: When antibodies are directly injected into a person, as with Hepatitis B immune globulin, it provides immediate but temporary protection against the specific antigen.
- Antigenic stimulus given by vaccine (polio) is artificial active immunity: T Vaccines contain weakened or inactivated pathogens or their antigens. When introduced into the body, the immune system develops an active immune response with memory cells, providing long-term protection against the disease.
- The serum concentration of which of the following human IgG subclass is maximum ?
- IgG1
- IgG2
- IgG3
- IgG4
Answer and Explanation
Answer: IgG1
Among the human IgG subclasses, IgG1 typically has the highest serum concentration.
The other options are incorrect:
- IgG2: IgG2 is one of the human IgG subclasses but does not have the maximum serum concentration.
- IgG3: IgG3 is another human IgG subclass but does not have the maximum serum concentration.
- IgG4: IgG4 is a human IgG subclass but does not have the maximum serum concentration.
- Function of T-lymphocyte is/are_____?
- Production of interferon
- Lymphokine production
- Rosette formation
- All of the above
Answer and Explanation
Answer: All of the above
Here’s a breakdown of the listed functions.
- Production of interferon: T cells can produce various interferons, which are signaling molecules that inhibit viral replication and activate other immune cells.
- Lymphokine production: Lymphokines is an older term encompassing various soluble factors secreted by T cells. These factors include interleukins, chemokines, and growth factors that influence the immune response by regulating the activation, proliferation, and differentiation of other immune cells.
- Rosette formation: This is not a function of T cells, but rather a test used to identify B cells. B cells form rosettes with sheep red blood cells due to the presence of surface receptors for sheep red blood cell antigens.
- Heptane is______?
- Same as epitopes
- Carrier required for specific antibody production
- High molecular protein
- None of the above
Answer and Explanation
Answer: Carrier required for specific antibody production
Heptane is a carrier molecule often used in immunology to conjugate with small molecules or haptens, enabling their recognition by the immune system and specific antibody production.
The other options are incorrect:
- Same as epitopes: Heptane is not the same as epitopes. Epitopes are specific regions on antigens recognized by antibodies or T cells.
- High molecular protein: Heptane is not a high molecular protein; it is a small hydrocarbon molecule used as a carrier.
- None of the above: The correct option is that heptane is a carrier required for specific antibody production.
- Delayed tuberculin test response is due to______?
- B lymphocytes
- T lymphocytes
- Monocytes
- Histiocytes
Answer and Explanation
Answer: T lymphocytes
The delayed tuberculin test response, such as the Mantoux test for tuberculosis, is due to the activation of T lymphocytes. T lymphocytes recognize antigens presented by antigen-presenting cells (APCs) in the context of major histocompatibility complex (MHC) molecules, leading to the delayed hypersensitivity reaction observed in the test.
The other options are incorrect:
- B lymphocytes: While B cells produce antibodies, they are not directly involved in the cell-mediated response measured by a TST.
- Monocytes: Monocytes are phagocytic cells that can ingest pathogens but are not the primary mediators of the delayed hypersensitivity reaction in a TST.
- Histiocytes: Histiocytes are tissue macrophages derived from monocytes. They can be involved in the inflammatory response at the injection site, but T cell activation is the key trigger.
- VDRL is a______?
- Slide flocculation test
- Tube flocculation test
- Tube agglutination test
- Latex agglutination test
Answer and Explanation
Answer: Slide flocculation test
The Venereal Disease Research Laboratory (VDRL) test is a slide flocculation test used for the screening of syphilis. It detects the presence of antibodies produced by the body in response to the Treponema pallidum bacteria, the causative agent of syphilis.
The other options are incorrect:
- Tube flocculation test: While flocculation can occur in tubes, the VDRL test specifically utilizes a slide format for observation of antigen-antibody aggregates.
- Tube agglutination test: Agglutination refers to the clumping of cells or particles, which can be used in some tests. However, the VDRL test relies on flocculation, involving the formation of loose, cloudy aggregates.
- Latex agglutination test: Latex agglutination tests use latex beads coated with antigens to detect antibodies. While rapid tests for syphilis may use this principle, the VDRL test is a different method.
- Secretory piece of IgA is synthesized in____?
- T-cells
- B-cells
- Lymph nodes
- Mucosal epithelium
Answer and Explanation
Answer: Mucosal epithelium
The secretory component, which forms the secretory piece of IgA (sIgA), is synthesized and added to IgA molecules by epithelial cells in mucosal tissues like the gut, respiratory tract, and genitourinary tract. This secretory component helps protect IgA from degradation in these environments and facilitates its transport across mucosal surfaces.
The other options are incorrect:
- T-cells: T-cells are involved in cell-mediated immunity, not the production of antibody components like the secretory piece of IgA.
- B-cells: While B-cells produce IgA antibodies, they don’t synthesize the secretory component.
- Lymph nodes: Lymph nodes are lymphoid organs that house immune cells but don’t directly synthesize the secretory component.
- Immunoglobulin consists of______?
- 2 light, 2 heavy chains
- 1 heavy, 2 light chains
- 1 light, 1 heavy chain
- 3 light, 1 heavy chain
Answer and Explanation
Answer: 2 light, 2 heavy chains
Immunoglobulins, also known as antibodies, consist of two identical heavy chains and two identical light chains. These chains are held together by disulfide bonds and non-covalent interactions.
The other options are incorrect:
- 1 heavy, 2 light chains: This is not the typical structure of an immunoglobulin molecule.
- 1 light, 1 heavy chain: This would be an incomplete antibody molecule and wouldn’t have the functional structure for antigen binding.
- 3 light, 1 heavy chain: This arrangement is not found in any known immunoglobulin structure.
- The exact part of the antigen that reacts with the immune system is called as_____?
- Clone
- Epitope
- Idiotope
- Paratope
Answer and Explanation
Answer: Epitope
An epitope is the specific region on an antigen molecule that is recognized and bound by antibodies or T-cell receptors. It’s the smallest part of the antigen that triggers an immune response.
The other options are incorrect:
- Clone: A clone refers to a population of genetically identical cells derived from a single parent cell. It’s not a specific part of the antigen.
- Idiotope: An idiotope is a specific region on an antibody molecule that can be recognized by other antibodies. It’s not part of the antigen itself.
- Paratope: The paratope is the complementary antigen-binding site on an antibody molecule that specifically fits the epitope on the antigen.pen_spark It’s the counterpart of the epitope on the antibody side.
- Phagocytosis enhanced by coating the surface of antigen is called______?
- Opsonization
- Chemotaxis
- De coding
- CFT
Answer and Explanation
Answer: Opsonization
Opsonization is the process by which antigens are coated with specific molecules (opsonins) that enhance their recognition and subsequent phagocytosis by phagocytic cells like macrophages and neutrophils. Opsonins act as tags, making the antigen more “visible” and palatable for the phagocytes.
The other options are incorrect:
- Chemotaxis: This refers to the directed movement of immune cells towards a chemical stimulus, not the specific coating of antigens.
- Decoding: This term isn’t typically used in the context of phagocytosis. The immune system doesn’t need to decode antigens, but rather recognizes specific patterns.
- CFT (Complement Fixation Test): This is a laboratory test used to detect the presence of complement activation, which can be involved in opsonization, but it’s not the process itself.
- Which of the following is a live vaccine______?
- 17 D
- Salk
- Hepatitis
- HDCV
Answer and Explanation
Answer: 17 D
17D is the strain of the yellow fever virus used in the live, attenuated yellow fever vaccine. This vaccine contains a weakened form of the virus that can replicate slightly in the body, but not enough to cause the full-blown disease. This triggers the immune system to develop a strong and lasting immunity against yellow fever.
The other options are incorrect:
- Salk: The Salk vaccine is an inactivated polio vaccine. It contains the inactivated poliovirus, which cannot replicate and cause disease.
- Hepatitis B Vaccine: This is another type of inactivated vaccine.
- HDCV (Hepatitis D Vaccine): This vaccine doesn’t exist yet because Hepatitis D requires the presence of Hepatitis B for infection.
- The killer cells are associated with immunologic response_______?
- Type I
- Type II
- Type III
- Type IV
Answer and Explanation
Answer: Type I
Type I hypersensitivity, also known as immediate hypersensitivity, involves the release of chemicals like histamine from immune cells like mast cells. Killer cells, also known as natural killer (NK) cells, are involved in a different type of immune response (innate) and don’t directly participate in Type I reactions.
The other options are incorrect:
- Type II: This type involves antibodies binding to antigens on the surface of cells, leading to destruction by immune system components. While NK cells can target some cells, they don’t rely on antibodies.
- Type III: This type involves immune complexes (antigen-antibody) depositing in tissues and causing inflammation. Not directly related to NK cell function.
- Type IV: This type is a cell-mediated immune response involving T cells. While NK cells are also lymphocytes, they belong to the innate immune system and have a different function compared to T cells in Type IV hypersensitivity.
FAQs:
What is immunology?
Immunology is the branch of biomedical science that deals with the study of the immune system, its functions, and disorders.
What is the immune system?
The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful invaders like bacteria, viruses, and parasites.
What are the main components of the immune system?
The main components include white blood cells (leukocytes), antibodies, the complement system, lymphatic system, spleen, thymus, and bone marrow.
What are the two types of immunity?
The two types are innate immunity (the body’s initial, non-specific defense mechanism) and adaptive immunity (a specific response developed over time).
How does the innate immune system work?
It acts as the first line of defense, using physical barriers (like skin), chemical signals, and immune cells (like macrophages and neutrophils) to prevent and control infections.
What is adaptive immunity?
Adaptive immunity is a targeted and specific immune response involving the activation of lymphocytes (B cells and T cells) that remember past infections for faster response in future encounters.
What are antibodies?
Antibodies, or immunoglobulins, are proteins produced by B cells that specifically bind to antigens (foreign substances) to neutralize or mark them for destruction.
What are antigens?
Antigens are molecules or molecular structures that are recognized by the immune system as foreign, prompting an immune response.
What role do T cells play in the immune response?
T cells are critical for cell-mediated immunity. They help destroy infected or cancerous cells and assist other immune cells in the immune response.
What is the difference between a vaccine and an antibody treatment?
A vaccine stimulates the immune system to develop immunity against a specific pathogen, whereas antibody treatments provide immediate, but temporary, passive immunity by introducing antibodies directly.
How do vaccines work?
Vaccines work by mimicking infectious agents, prompting the immune system to produce a response and memory cells without causing the disease.
What is an autoimmune disease?
An autoimmune disease occurs when the immune system mistakenly attacks the body’s own healthy cells and tissues.
What are some common autoimmune diseases?
Common autoimmune diseases include rheumatoid arthritis, lupus, type 1 diabetes, and multiple sclerosis.
What is immunodeficiency?
Immunodeficiency refers to a state where the immune system’s ability to fight infectious disease is compromised or entirely absent.
What are primary and secondary immunodeficiencies?
Primary immunodeficiencies are usually genetic and present at birth, while secondary immunodeficiencies are acquired due to external factors such as infections (e.g., HIV/AIDS), malnutrition, or chemotherapy.
What is an allergic reaction?
An allergic reaction is an exaggerated immune response to a normally harmless substance, known as an allergen.
What are cytokines?
Cytokines are signaling proteins released by cells that play a crucial role in cell signaling in the immune system, regulating immunity, inflammation, and hematopoiesis.
How does the immune system differentiate between self and non-self?
The immune system uses a set of molecules known as Major Histocompatibility Complex (MHC) to distinguish between self and non-self. Cells displaying self-MHC molecules are typically left alone, while those with foreign MHC or antigens are targeted.
Can stress affect the immune system?
Yes, chronic stress can suppress immune function, making the body more susceptible to infections and diseases.
What is immunotherapy?
Immunotherapy is a type of treatment that uses certain parts of a person’s immune system to fight diseases such as cancer. This can include stimulating the immune system to work harder or smarter, or providing the immune system with components like antibodies.
Possible References Used