Immunology and Serology MCQs with Answer and Explanations | Chapter 10

Answer: Live attenuated vaccine

Live attenuated vaccines contain weakened forms of the disease-causing microorganism. A single dose of a live attenuated vaccine is often sufficient to induce a robust immune response and confer long-lasting immunity against the disease.

The other options are incorrect:

• Killed vaccine: Killed vaccines contain inactivated forms of the disease-causing microorganism. They typically require multiple doses or booster shots to provide adequate immunity.
• Taxoids: Taxoids are a class of drugs used in chemotherapy, not vaccines.
• None of the above: This option is incorrect because live attenuated vaccines can often provide sufficient immunization with a single dose.

Answer: Syphilis

The VDRL (Venereal Disease Research Laboratory) test is a screening test used for the diagnosis of syphilis. It detects the presence of antibodies produced in response to Treponema pallidum, the bacterium that causes syphilis.

The other options are incorrect:

• Tuberculosis: Tuberculosis is not diagnosed using the VDRL test. Tuberculosis is typically diagnosed through methods such as sputum culture, chest X-rays, and tuberculin skin tests.
• Pneumonia: The VDRL test is not used for the diagnosis of pneumonia. Pneumonia is diagnosed based on symptoms, physical examination, and imaging studies such as chest X-rays.
• AIDS: The VDRL test is not used for the diagnosis of AIDS (Acquired Immunodeficiency Syndrome). AIDS is diagnosed based on clinical criteria and laboratory tests to detect HIV infection.

Answer: AIDS

ELISA (Enzyme-Linked Immunosorbent Assay) is commonly used for the diagnosis of AIDS (Acquired Immunodeficiency Syndrome) by detecting antibodies or antigens associated with HIV (Human Immunodeficiency Virus) infection in blood samples.

The other options are incorrect:

• Night blindness: ELISA is not used for the diagnosis of night blindness. Night blindness is often related to vitamin A deficiency or other underlying eye conditions and is diagnosed through clinical evaluation and specific tests related to eye health.
• Sickle cell anaemia: ELISA is not used for the diagnosis of sickle cell anemia. Sickle cell anemia is diagnosed through hemoglobin electrophoresis or other specialized tests that detect abnormal hemoglobin variants characteristic of the disease.
• All of the above: This option is incorrect because ELISA is not used for the diagnosis of night blindness or sickle cell anemia. It is primarily used for the diagnosis of HIV/AIDS.

Answer: IgM Anti HBc antobody

Acute hepatitis B infection is best diagnosed by detecting IgM antibodies against hepatitis B core antigen (IgM Anti HBc). IgM Anti HBc antibodies appear early in the course of infection and indicate recent or acute hepatitis B infection.

The other options are incorrect:

• HBsAg: HBsAg (Hepatitis B surface antigen) indicates the presence of hepatitis B virus and is typically detected during the acute and chronic phases of infection, but it does not specifically indicate acute infection.
• HBeAg: HBeAg (Hepatitis B e antigen) is a marker of active viral replication in chronic hepatitis B infection, but its presence does not specifically indicate acute infection.
• HBcAg: HBcAg (Hepatitis B core antigen) is not routinely used for the diagnosis of acute hepatitis B infection. It is mainly detected in liver tissue and is not commonly used in diagnostic testing.

Answer: IgM Anti HBc antobody

IgM anti-HBc antibody is the best marker for diagnosing acute hepatitis B infection. Its presence indicates recent or acute infection, as IgM antibodies are typically produced early in the course of infection.

The other options are incorrect:

• HBsAg: HBsAg is a marker of hepatitis B virus infection but does not specifically indicate acute infection. It can be detected during acute and chronic phases of infection.
• HBeAg: HBeAg is a marker of active viral replication in chronic hepatitis B infection, not specifically indicative of acute infection.
• HBcAg: HBcAg is not routinely detected in diagnostic tests for hepatitis B infection. It is mainly found in liver tissue and is not used for diagnosing acute infection.

Answer: IgG

IgG is the only antibody that efficiently crosses the placenta from the mother to the fetus, providing passive immunity to the newborn during the early months of life.

The other options are incorrect:

• IgA: IgA is primarily found in mucosal secretions like saliva and breast milk but does not cross the placenta in significant amounts.
• IgE: IgE antibodies are involved in allergic responses and are not known to cross the placenta.
• IgM: IgM antibodies are too large to cross the placenta efficiently and do not provide passive immunity to the fetus.

Answer: IgA

IgA is an example of surface Ig, also known as sIg or membrane Ig. It is found on the surface of mucosal epithelial cells and plays a crucial role in mucosal immunity, particularly in defense against pathogens at mucosal surfaces.

The other options are incorrect:

• IgG: IgG is primarily found in the bloodstream and interstitial fluids, where it provides systemic immunity rather than mucosal immunity.
• IgE: IgE antibodies are involved in allergic responses and are not typically associated with mucosal surfaces.
• IgM: IgM antibodies are present mainly in the bloodstream and are not typically associated with mucosal surfaces.

Answer: IgE

Type I hypersensitivity reactions, also known as immediate hypersensitivity reactions or allergic reactions, are mediated by IgE antibodies. IgE antibodies bind to mast cells and basophils, sensitizing them to allergens and triggering the release of inflammatory mediators upon re-exposure to the allergen.

The other options are incorrect:

• IgA: IgA antibodies are primarily found in mucosal secretions and are not involved in Type I hypersensitivity reactions.
• IgG: IgG antibodies are involved in various immune responses, including secondary immune responses and some types of hypersensitivity reactions, but they are not specifically associated with Type I hypersensitivity.
• IgM: IgM antibodies are mainly involved in primary immune responses and are not typically associated with Type I hypersensitivity reactions.

Answer: Type I

Wheal and flare reactions are characteristic of Type I hypersensitivity reactions. In this type of reaction, exposure to an allergen triggers the release of histamine and other inflammatory mediators, leading to localized swelling (wheal) and redness (flare) at the site of allergen exposure.

The other options are incorrect:

• Type II: Type II hypersensitivity reactions involve cytotoxic antibodies targeting specific cells or tissues, leading to cell destruction. They do not typically manifest as wheal and flare reactions.
• Type IV: Type IV hypersensitivity reactions, also known as delayed-type hypersensitivity reactions, involve T cell-mediated immune responses and do not typically present as wheal and flare reactions.
• Type V: Type V hypersensitivity reactions are not a recognized category of hypersensitivity reactions.

Answer: Autoimmune hemolytic anemia

Type I hypersensitivity reactions are immediate allergic reactions mediated by IgE antibodies and mast cell activation. They involve the release of inflammatory mediators such as histamine and cytokines, leading to symptoms like itching, hives, and asthma. Autoimmune hemolytic anemia, on the other hand, is a Type II hypersensitivity reaction where antibodies target antigens on the surface of red blood cells, leading to their destruction.

The other options are incorrect:

• Anaphylaxis: Anaphylaxis is a severe, systemic allergic reaction that is a classic example of Type I hypersensitivity.
• Extrinsic asthma: Extrinsic asthma, also known as allergic asthma, is caused by allergens triggering Type I hypersensitivity reactions in the airways, leading to bronchoconstriction and asthma symptoms.
• Hay fever: Hay fever, or allergic rhinitis, is an allergic reaction to airborne allergens such as pollen, which triggers Type I hypersensitivity reactions in the nasal mucosa, leading to symptoms like sneezing, runny nose, and nasal congestion.

Answer: Type IV hypersensitivity

A positive tuberculin test, also known as a Mantoux test, is an example of Type IV hypersensitivity reaction. In this type of reaction, there is a delayed cell-mediated immune response to an antigen, which in the case of the tuberculin test, is the purified protein derivative (PPD) derived from Mycobacterium tuberculosis.

The other options are incorrect:

• Type I hypersensitivity: Type I hypersensitivity reactions, also known as immediate hypersensitivity reactions, involve the release of histamine and other mediators from mast cells and basophils upon exposure to an allergen. They are associated with conditions such as allergic rhinitis, asthma, and anaphylaxis.
• Type II hypersensitivity: Type II hypersensitivity reactions involve the production of antibodies that bind to antigens on the surface of cells or tissues, leading to cell destruction. Examples include autoimmune hemolytic anemia and certain drug reactions.
• Type III hypersensitivity: Type III hypersensitivity reactions involve the formation of immune complexes that deposit in tissues, triggering inflammation and tissue damage. Examples include systemic lupus erythematosus and serum sickness.

Answer: Second set rejection

When a skin graft from the same donor is applied for the second time, the recipient’s immune system has already been sensitized to the donor’s antigens. This sensitization results in accelerated rejection known as second set rejection.

Incorrect Options:

• First set rejection: First set rejection occurs when a graft from a donor is applied to a recipient for the first time and is rejected due to the recipient’s immune response.
• Both: The rejection occurring when a graft is applied for the second time is specifically referred to as second set rejection, so the option “Both” is incorrect.
• None: Rejection of a graft upon repeat application is a known phenomenon, so the option “None” is incorrect.

Answer: Isograft

An isograft refers to a transplant where the recipient and donor are genetically identical. This means their tissues share the same histocompatibility antigens, eliminating the risk of immune rejection.

The other options are incorrect:

• Autograft: This refers to a graft where the recipient and donor are the same individual. For example, skin taken from one area of the body and transplanted to another.
• Allograft: This refers to a transplant where the recipient and donor are of the same species but genetically different. In this case, the recipient’s immune system might recognize the donor’s tissue as foreign and reject the transplant.
• Xenograft: This refers to a transplant where the recipient and donor are from different species. Xenografts are very challenging due to significant incompatibility between tissues and are rarely successful.

Answer: Salk polio vaccine

Live-attenuated vaccines contain weakened versions of a virus or bacteria that can still replicate in the body but don’t cause the full-blown disease. This stimulates the immune system to develop immunity. The Salk polio vaccine, however, is an inactivated vaccine, meaning the poliovirus particles are killed and cannot replicate.

The other options are incorrect:

• MMR (measles, mumps, rubella): This is a live-attenuated vaccine that combines weakened forms of the measles, mumps, and rubella viruses.
• Yellow fever 17D vaccine: This is a live-attenuated vaccine derived from a weakened strain of the yellow fever virus.
• Sabin polio vaccine: This is another live-attenuated vaccine that contains weakened poliovirus strains to provide immunity against polio.

Answer: IgE

IgE is more sensitive to heat and can be inactivated at higher temperatures compared to other immunoglobulins.

The other options are incorrect:

• IgG: This is the most abundant immunoglobulin in the blood and is relatively stable at higher temperatures.
• IgA: This immunoglobulin is found in mucous membranes and bodily secretions and has moderate heat stability.
• IgM: This is the first immunoglobulin produced in response to an infection and is relatively stable at higher temperatures.

Answer: Glycoproteins

Immunoglobulins, also known as antibodies, are proteins produced by the immune system. They have a Y-shaped structure and contain attached carbohydrate chains, making them glycoproteins. These carbohydrates play a role in the function and stability of the antibodies.

The other options are incorrect:

• Glycolipids: These are molecules with sugar molecules attached to lipids (fats). They are not involved in the immune response.
• Polypeptides: These are simply chains of amino acids, the building blocks of proteins. Immunoglobulins are more complex than just a chain of amino acids, with a specific folded structure.
• Proteoglycans: These are complex molecules consisting of a protein core with glycosaminoglycan chains attached. While they are involved in various biological processes, they are not directly related to the immune response like immunoglobulins.

Answer: immunogenicity

An adjuvant is a substance added to some vaccines to enhance the immune response (immunogenicity) to the antigen in the vaccine. This can be achieved by stimulating the immune system in various ways, such as by creating a depot effect at the injection site or by activating antigen-presenting cells.

The other options are incorrect:

• Distribution: Adjuvants do not directly affect the distribution of the vaccine in the body. They primarily focus on enhancing the immune response at the injection site.
• Absorption: Similar to distribution, adjuvants are not primarily concerned with absorption. The body’s natural processes handle absorption of the vaccine.
• Shelf life: Adjuvants may have some influence on the stability of the vaccine, but enhancing shelf life is not their main function. They are primarily used to improve the effectiveness of the vaccine.

Answer: Natural passive immunity

When a pregnant woman receives a tetanus toxoid vaccine, she develops antibodies against tetanus. These antibodies can then cross the placenta and pass to the developing baby. This provides the infant with short-term protection against tetanus until they can receive their own vaccinations. This type of immunity acquired from the mother is called natural passive immunity.

The other options are incorrect:

• Innate immunity: This is the body’s nonspecific defense system present at birth and doesn’t involve antibodies.
• Natural active immunity: This occurs when an individual develops immunity after exposure to a natural infection. The infant isn’t directly exposed to tetanus in this scenario.
• Artificial active immunity: This is immunity acquired through vaccination, but the vaccination is given directly to the infant, not the mother.

Answer: Artificial passive immunity

Anti-D immunoglobulin (RhIg) is given to a Rh-negative pregnant woman with a Rh-positive fetus to prevent hemolytic disease of the newborn. This is an example of artificial passive immunity because the woman is given pre-formed antibodies.

The other options are incorrect:

• Artificial active immunity: Involves the stimulation of the immune system to produce antibodies through vaccination.
• Natural passive immunity: Involves the transfer of antibodies from mother to child naturally, either through the placenta or breast milk.
• Adoptive immunity: Involves the transfer of immune cells from a donor to a recipient, usually in the context of certain therapies or treatments.

Answer: Type Il hypersensitivity

Graves’ disease is an autoimmune disorder in which antibodies target the thyroid-stimulating hormone receptor (TSHR) on thyroid cells, leading to hyperthyroidism. This antibody-mediated cytotoxic reaction characterizes Type II hypersensitivity.

The other options are incorrect:

• Type I hypersensitivity: Involves IgE-mediated allergic reactions, such as anaphylaxis, asthma, and hay fever.
• Type III hypersensitivity: Involves immune complex-mediated reactions, where antigen-antibody complexes deposit in tissues, leading to inflammation, as seen in conditions like systemic lupus erythematosus.
• Type IV hypersensitivity: Involves T-cell-mediated delayed-type hypersensitivity reactions, such as contact dermatitis and tuberculin reactions.

Answer: Type Il hypersensitivity

Rh incompatibility involves Type II hypersensitivity, where maternal antibodies target Rh-positive fetal red blood cells, leading to hemolysis.

The other options are incorrect:

• Type I hypersensitivity: This involves IgE-mediated allergic reactions, such as anaphylaxis, asthma, and hay fever.
• Type III hypersensitivity: This involves immune complex-mediated reactions, where antigen-antibody complexes deposit in tissues, causing inflammation, as seen in conditions like systemic lupus erythematosus.
• Type IV hypersensitivity: This involves T-cell-mediated delayed-type hypersensitivity reactions, such as contact dermatitis and tuberculin reactions.

Answer: Any of the above

Antigens are molecules that can trigger an immune response in the body. They come in a variety of chemical forms, including:

• Lipids: Fats or fat-like molecules can sometimes act as antigens, especially when combined with carrier proteins.
• Polysaccharides: Complex sugars can be recognized by the immune system as foreign and trigger an immune response.
• Proteins: These are the most common type of antigen. The immune system can recognize specific shapes and features on protein molecules and generate antibodies against them.

Answer: Tuberculin test

The tuberculin test is an example of cell-mediated (Type IV) hypersensitivity. This type of hypersensitivity involves T-cell mediated immune responses, which lead to tissue damage at the site of antigen exposure, typically seen 48-72 hours after the test.

The other options are incorrect:

• Transfusion reactions: These are typically Type II hypersensitivity reactions, where antibodies target foreign red blood cells, leading to their destruction.
• Arthus reactions: These are Type III hypersensitivity reactions, which involve immune complex deposition in tissues, causing inflammation and tissue damage.
• Type II lepra reaction: This involves Type III hypersensitivity reactions, where immune complexes contribute to the inflammatory process.

Answer: Type IV hypersensitivity

The tuberculin test is an example of Type IV hypersensitivity, also known as delayed-type hypersensitivity (DTH). It is mediated by T cells, which recognize antigens and release cytokines that attract macrophages and other immune cells to the site, causing inflammation and induration.

The other options are incorrect:

• Type I hypersensitivity: This involves IgE-mediated allergic reactions, such as anaphylaxis, asthma, and hay fever, which occur immediately after exposure to an allergen.
• Type II hypersensitivity: This involves antibody-mediated cytotoxic reactions where antibodies target antigens on cell surfaces, leading to cell destruction, as seen in transfusion reactions and autoimmune hemolytic anemia.
• Type III hypersensitivity: This involves immune complex-mediated reactions, where antigen-antibody complexes deposit in tissues, causing inflammation and tissue damage, as seen in conditions like systemic lupus erythematosus and Arthus reactions.

Answer: 250-500 units

The recommended dose of human tetanus immunoglobulin (TIG) for post-exposure prophylaxis in non-immune individuals is typically 250-500 units. This dose provides immediate passive immunity against the tetanus toxin.

The other options are incorrect:

• 500-750 units: This range is higher than the standard recommended dose and is not typically used for routine post-exposure prophylaxis.
• 750-1000 units: This range is also higher than the standard recommended dose and not typically used for routine post-exposure prophylaxis.
• 1000-1200 units: This range is significantly higher than the standard recommended dose and is not typical for post-exposure prophylaxis.

Answer: Syphilis

The VDRL (Venereal Disease Research Laboratory) test is a screening tool specifically designed to detect antibodies produced by the body in response to a syphilis infection.

The other options are incorrect:

• HIV: HIV diagnosis relies on tests that directly detect the presence of the HIV virus or its antibodies. VDRL is not specific to HIV and wouldn’t be used for this purpose.
• Typhoid: Typhoid fever is diagnosed through blood tests that identify the Salmonella Typhi bacteria causing the infection. VDRL is not relevant to typhoid diagnosis.
• Tuberculosis: While both syphilis and tuberculosis involve immune responses, the VDRL test is not specific for the bacteria causing tuberculosis. Different diagnostic tests are used for TB detection.

Answer: 5 IU

The usual dose of purified protein derivative (PPD) used in the Mantoux test is 5 IU (International Units). This dose is injected intradermally to test for tuberculosis infection.

The other options are incorrect:

• 50 IU: This is significantly higher than the standard dose and could lead to excessive local reactions and false-positive results.
• 100 IU: This is also much higher than the standard dose and not used for routine Mantoux testing.
• 500 IU: This dose is extremely high and inappropriate for the Mantoux test, likely causing severe reactions and inaccurate results.

Answer: 10mm

A positive Mantoux test is generally defined by an area of induration measuring 10mm or more in diameter, which indicates exposure to Mycobacterium tuberculosis or a prior BCG vaccination.

The other options are incorrect:

• 6-9mm: An induration of 6-9mm is typically considered a borderline or doubtful result and may require further evaluation depending on the individual’s risk factors and clinical context.
• <5mm: An induration less than 5mm is generally considered negative, indicating no significant exposure or infection.
• >20mm: While an induration greater than 20mm is certainly positive, it is more specific to consider the threshold at 10mm for typical diagnostic purposes.

Answer: h Ag

Individuals with the Bombay blood group (Oh) lack the H antigen on their red blood cells and instead have the h antigen. This unique feature means they do not express A or B antigens and cannot receive blood from A, B, AB, or even O blood types that have the H antigen.

The other options are incorrect:

• A Ag: Individuals with the A blood type have the A antigen on their red blood cells. This is not present in Bombay blood group individuals.
• B Ag: Individuals with the B blood type have the B antigen on their red blood cells. This is not present in Bombay blood group individuals.
• H Ag: Most individuals with the O blood type have the H antigen on their red blood cells. However, individuals with the Bombay blood group lack the H antigen and instead have the h antigen.

Answer: I_g A

Immunoglobulin A (IgA) provides local immunity, particularly in mucosal surfaces such as the gastrointestinal tract, respiratory tract, and urogenital tract. It plays a crucial role in the immune function of mucous membranes by preventing the attachment and invasion of pathogens.

The other options are incorrect:

• IgM: This is the first antibody produced in response to an infection and is primarily found in the blood and lymphatic fluid. It is important in the initial stages of immune response but not specifically associated with local immunity.
• IgD: This immunoglobulin is present in small amounts in the blood and is primarily involved in the activation and regulation of B cells, not specifically in providing local immunity.
• IgG: This is the most abundant immunoglobulin in the blood and is crucial for systemic immunity. It can cross the placenta to provide passive immunity to the fetus but is not primarily associated with local immunity at mucosal surfaces.

Answer: Western blot

The Western blot test is used as a confirmatory test for AIDS (Acquired Immunodeficiency Syndrome) after an initial positive result from a screening test like ELISA. It detects specific proteins related to HIV, thereby confirming the presence of the virus.

The other options are incorrect:

• Southern blot: This technique is used to detect specific DNA sequences in DNA samples and is not used for confirming HIV/AIDS.
• ELISA: While ELISA (Enzyme-Linked Immunosorbent Assay) is a commonly used screening test for HIV, it is not a confirmatory test. ELISA is used to detect antibodies to HIV in the blood.
• CLIA: Chemiluminescent immunoassay (CLIA) is another method used for screening and initial testing but is not typically used as a confirmatory test for HIV/AIDS.

Answer: syphilis.

RPR (Rapid Plasma Reagin) and VDRL (Venereal Disease Research Laboratory) tests are both used for the diagnosis of syphilis. They detect antibodies produced by the body in response to the bacterium Treponema pallidum, which causes syphilis.

The other options are incorrect:

• AIDS: These tests are not used for the diagnosis of AIDS (Acquired Immunodeficiency Syndrome). AIDS is diagnosed through specific tests for detecting HIV (Human Immunodeficiency Virus) antibodies or antigens.
• Hepatitis: RPR and VDRL tests are not used for diagnosing hepatitis. Hepatitis is diagnosed through specific tests for detecting hepatitis viruses or markers of liver inflammation.
• Malaria: These tests are not used for diagnosing malaria. Malaria is diagnosed through blood tests to detect the presence of the malaria parasite or its antigens.

Answer: Coombs test

The Coombs test, also known as the antiglobulin test, is used to detect incomplete antibodies or antibodies that are bound to the surface of red blood cells. It helps in diagnosing autoimmune hemolytic anemia and certain other autoimmune disorders.

The other options are incorrect:

• Electrophoresis: Electrophoresis is a technique used to separate proteins based on their size and charge. It is not specifically used to detect incomplete antibodies.
• Agglutination test: Agglutination tests, such as the blood typing tests, are used to detect the presence of specific antibodies that cause clumping or aggregation of cells. They are not typically used to detect incomplete antibodies.
• VDRL test: The VDRL (Venereal Disease Research Laboratory) test is used for screening and diagnosing syphilis, not for detecting incomplete antibodies.

Answer: IL-1

IL-1 (Interleukin-1) is a multilineage cytokine, meaning it can act on and influence various cell types involved in the immune response. It plays a crucial role in initiating inflammation and immune defense mechanisms.

The other options are incorrect:

• IL-2: While important for T cell activation and proliferation, IL-2 primarily targets T lymphocytes and wouldn’t be classified as multilineage.
• IL-3: This cytokine mainly affects hematopoietic stem cells and progenitor cells, promoting the development of various blood cell types like red blood cells, white blood cells, and platelets. Its influence is limited to these lineages.
• IL-4: IL-4 is primarily involved in promoting B cell activation and antibody production, along with functions in allergic responses. It wouldn’t be considered multilineage due to its more specific cellular targets.

Answer: NK cells

Large Granular Lymphocytes (LGLs) are a type of lymphocyte characterized by their large size and granular appearance when viewed under a microscope. Natural Killer (NK) cells are a subset of LGLs that play a critical role in the innate immune response by recognizing and destroying virus-infected cells and tumor cells.

The other options are incorrect:

• Plasma cells: Plasma cells are differentiated B lymphocytes that produce antibodies. They are not typically referred to as Large Granular Lymphocytes.
• T-cells: T-cells are a type of lymphocyte involved in cell-mediated immunity, including the activation of other immune cells and the destruction of infected or abnormal cells. They are not typically referred to as Large Granular Lymphocytes.
• K-cells: There is no specific cell type known as “K-cells” in the context of immunology.

Answer: CD3

CD3 is the most reliable and specific pan T-cell marker. It’s a co-receptor molecule present on all mature T cells throughout their development and function. Its presence signifies a mature T cell.

The other options are incorrect:

• CD-2: While CD2 is also expressed on most mature T cells, it can be found on some other cell types like natural killer (NK) cells. Therefore, it’s not as specific for T cells as CD3.
• CD19: This marker is specific for B cells, not T cells. It’s crucial for B cell development and function.
• CD25: CD25 is the IL-2 receptor alpha chain. While it’s expressed on activated T cells, it’s not present on all T cells and can also be found on some regulatory T cells. Therefore, it’s not a reliable pan T-cell marker.

Answer: The chains are formed by genetic rearrangement after maturation

The statement that the chains of immunoglobulin (Ig) molecules are formed by genetic rearrangement after maturation is true. During B cell development, genetic rearrangement processes, such as V(D)J recombination, occur to generate the diverse repertoire of Ig molecules. This process involves the rearrangement of gene segments encoding the variable (V), diversity (D), and joining (J) regions of the Ig heavy and light chains.

The other options are incorrect:

• Coded in the same site of a chromosome: This is incorrect because the genes encoding the different chains of Ig molecules (heavy and light chains) are located on different chromosomes.
• Coded in the different site of a chromosome: This is incorrect because the genes encoding the different chains of Ig molecules are not located on the same chromosome.
• Different chains of the same Ig are coded by the same chromosome: This is incorrect because the genes encoding the heavy and light chains of Ig molecules are located on different chromosomes.

Answer: HBsAg +, HBeAg +, Anti-HBcIgM +, Anti-HBs -, Anti-HBe –

During the acute phase of highly infectious Hepatitis B Virus (HBV) infection, the serological profile typically includes the presence of HBsAg (surface antigen) and HBeAg (e antigen) in the blood. Additionally, there is usually a presence of IgM antibodies against HBcAg (core antigen) indicating recent infection. Anti-HBs (antibodies against HBsAg) and Anti-HBe (antibodies against HBeAg) are typically absent during the acute phase.

The other options are incorrect:

• HBsAg +, HBeAg +, Anti-HBcIgM -, Anti-HBs -, Anti-HBe -: This profile does not reflect an acute HBV infection as it lacks IgM antibodies against HBcAg.
• HBsAg – ,HBeAg-, Anti-HBcIgM -, Anti-HBs +, Anti-HBe -: This profile indicates past infection or immunity to HBV, as there are antibodies against HBsAg and HBeAg, and absence of HBsAg and HBeAg.
• HBsAg -, HBeAg -, Anti-HBcIgG -, Anti-HBs +, Anti-HBe +: This profile also indicates past infection or immunity to HBV, as there are antibodies against HBsAg and HBeAg, and absence of HBsAg and HBeAg. Additionally, the presence of Anti-HBe indicates resolution of infection.

Answer: Immunology

Immunology is a dedicated field of biology that focuses on the study of immune systems across all living things, from plants and animals to even single-celled organisms.

The other options are incorrect:

• Zoology: While zoology studies animals, it doesn’t specifically focus on immune systems. It encompasses a broader range of animal biology.
• Microbiology: This field deals with microscopic organisms, including bacteria, viruses, and fungi. While some aspects of microbiology touch on immune system interactions with these microbes, it’s not the central focus.
• Biotechnology: Although biotechnology utilizes the immune system for various applications, it’s a broader field encompassing the manipulation of biological processes for various purposes, not just immunity.

Answer: Acquired immunity

Acquired immunity is the type of immunity you develop throughout your life in response to exposure to pathogens (through infection or vaccination) or receiving antibodies from another source.

The other options are incorrect:

• Active immunity: This is a subtype of acquired immunity where your body actively develops its own immune response after encountering a pathogen or receiving a vaccine. While it’s acquired during your lifetime, it’s a specific mechanism within the broader category.
• Passive immunity: This is another subtype of acquired immunity, but it involves receiving antibodies from another source (e.g., from a mother via breast milk or through antibody injections). It provides temporary protection but doesn’t involve your own immune system actively building memory.
• None of the above: Acquired immunity is a well-established concept, so this wouldn’t be the correct answer.

Answer: Five.

There are five main types of antibodies classified based on the structure of their heavy chains:

• IgM (Immunoglobulin M)
• IgD (Immunoglobulin D)
• IgG (Immunoglobulin G) – Most abundant in blood
• IgA (Immunoglobulin A)
• IgE (Immunoglobulin E)

The other options are incorrect:

• Three: It underestimates the number of antibody types. While there are more than three, the main classes are IgA, IgD, IgE, IgG, and IgM.
• Two: It significantly underestimates the diversity of antibody types. There are more than two, each with unique functions and properties.
• Four: It does not account for all the major types of antibodies. There are indeed five types, and excluding any would overlook key components of the immune system.

Answer: T cells

T cells are a type of lymphocyte, a white blood cell essential for cell-mediated immunity. They directly attack and destroy infected cells, cancer cells, and some pathogens.

The other options are incorrect:

• Leukaemia: This is not a cell type, but a type of cancer that affects white blood cells.
• Mast cells: These cells are involved in the allergic response, not cell-mediated immunity.
• Thrombocytes: These are also known as platelets and are involved in blood clotting, not immune response.

Answer: Immune system

The immune system is a complex network of specialized organs, cells, and proteins that defend the body against disease-causing pathogens like bacteria, viruses, and parasites. It has various mechanisms to identify and eliminate these threats.

The other options are incorrect:

• Respiratory System: While the respiratory system helps filter out some airborne pathogens, it’s not the primary defense against disease.
• Digestive System: The digestive system plays a role in breaking down food and absorbing nutrients but isn’t the main line of defense against pathogens. While some gut bacteria can help with immunity, the immune system itself is separate.

Answer: Recombinant Vaccine

Hepatitis vaccines are recombinant vaccines. These vaccines use genetically modified organisms to produce specific proteins from the virus. The immune system then recognizes these proteins and builds immunity against the actual virus.

The other options are incorrect:

• Subunit Vaccine: Subunit vaccines are a type of recombinant vaccine, but not all recombinant vaccines are for viruses. Hepatitis vaccines specifically target viral proteins.
• Killer Vaccine: There’s no category of vaccines called “killer vaccines.” Vaccines train the immune system to fight infections, not directly kill pathogens.
• Toxoids Vaccine: Toxoid vaccines are used for bacterial toxins, not viruses like hepatitis. They modify bacterial toxins to prevent them from causing harm.

Answer: IgM is primarily restricted in the circulation

Due to its large size and structure as a pentamer (five antibody units linked together), IgM has difficulty passing through tight junctions between cells. This restricts it mainly to the bloodstream.

The other options are incorrect:

• IgM can cross the placenta: IgM antibodies are too large to pass through the placenta and provide passive immunity to the fetus. IgG, a smaller antibody, can cross the placenta.
• IgM can protect the mucosal surface: While IgM can bind to pathogens, its large size limits its ability to access and effectively neutralize them on mucosal surfaces like the gut or respiratory tract. IgA is a more suitable antibody for this role.
• IgM is produced by high-affinity plasma cells: IgM is the first antibody produced in a primary immune response and typically has lower affinity (binding strength) compared to antibodies produced later (IgG) during the same immune response.

Answer: Cytokine barriers

Interferons are a type of cytokine. Cytokines are signaling molecules produced by cells that regulate the immune system and inflammation. Interferons specifically act as messengers between cells, triggering antiviral responses and activating immune cells.

The other options are incorrect:

• Physical barriers: These are structures like skin and mucous membranes that physically block pathogens from entering the body.
• Cellular barriers: These are specialized cells that form physical barriers, like epithelial cells in the skin or gut lining.
• Physiological barriers: These are factors like stomach acid or tears that create unfavorable environments for pathogens. While these barriers contribute to defense, they don’t involve cell signaling like interferons.

Answer: Basophil

Basophils are a type of white blood cell involved in allergic reactions and inflammation through the release of histamine, but they do not perform phagocytosis.

The other options are incorrect:

• Macrophage: Macrophages are highly effective phagocytic cells that reside in tissues and play a crucial role in engulfing pathogens and presenting them to other immune cells.
• Neutrophil: Neutrophils are the most abundant white blood cells and the first line of defense in phagocytosis. They are particularly effective against bacterial infections.
• Eosinophil: Eosinophils are phagocytic cells involved in allergic reactions and parasitic infections. They release enzymes that damage these types of threats.

Answer: Macrophage

Monocytes are a type of white blood cell that circulates in the bloodstream. When they encounter inflammation or infection signals, they migrate to tissues and differentiate into larger phagocytic cells called macrophages. Macrophages are essential for engulfing and destroying pathogens, cellular debris, and foreign particles.

The other options are incorrect:

• Neutrophil: Neutrophils are another type of phagocytic cell, but they develop from a different lineage in the bone marrow compared to monocytes. They are shorter-lived and more specialized for fighting bacterial infections.
• B cell: B cells are lymphocytes that mature in the bone marrow and become plasma cells, which produce antibodies. They are not phagocytic cells.
• T cell: T cells are another type of lymphocyte involved in cell-mediated immunity. They don’t directly engulf pathogens, but rather activate other immune cells and directly target infected or abnormal cells.

Answer: Either live-attenuated or killed

Vaccines against viruses typically fall into two main categories: live-attenuated vaccines, where the virus is weakened but still alive, or killed (inactivated) vaccines, where the virus is no longer active but still retains antigenic properties to stimulate the immune system

The other options are incorrect:

• Given at birth: While some vaccines are recommended shortly after birth, not all are given at birth. The specific timing of vaccinations depends on the disease and the immune system’s development.
• Expensive: Vaccine costs can vary, but many childhood vaccines are readily available and affordable through public health programs.
• Mainly polysaccharide: Polysaccharide vaccines are a specific type of vaccine used for some bacterial infections, not the main type for viruses. Viral vaccines typically target viral proteins.

Answer: Jenner

Edward Jenner is credited with inventing the world’s first successful vaccine, the smallpox vaccine, in 1796. He observed that people who had previously contracted cowpox, a milder disease related to smallpox, were immune to smallpox itself.

The other options are incorrect:

• Pasteur: Louis Pasteur made significant contributions to microbiology and immunology, developing vaccines for rabies, anthrax, and chicken cholera. However, he came after Jenner’s work on the smallpox vaccine.
• Koch: Robert Koch was a renowned microbiologist who discovered the causative agents for several diseases like tuberculosis and anthrax. While his work helped pave the way for vaccine development, he wasn’t directly involved in creating the first vaccine.
• Salk: Jonas Salk developed the first successful polio vaccine in the mid-20th century. This was a major breakthrough, but it came decades after Jenner’s work on smallpox.