Q.1 Which part of an antibody determines its antigen specificity?
Fc region
Fab region
Hinge region
Constant region
Explanation - The Fab region (Fragment antigen-binding) contains the variable region that recognizes and binds to a specific antigen.
Correct answer is: Fab region
Q.2 Which immunoglobulin is the first antibody produced in response to an infection?
IgG
IgM
IgA
IgE
Explanation - IgM is the primary antibody produced during the initial exposure to an antigen.
Correct answer is: IgM
Q.3 Which immunoglobulin is most abundant in human serum?
IgA
IgG
IgM
IgE
Explanation - IgG is the most abundant antibody in serum and provides long-term immunity.
Correct answer is: IgG
Q.4 Which antibody is mainly found in mucosal surfaces and secretions like saliva and breast milk?
IgG
IgA
IgM
IgE
Explanation - IgA protects mucosal surfaces and is abundant in secretions such as saliva, tears, and breast milk.
Correct answer is: IgA
Q.5 Which immunoglobulin is primarily involved in allergic reactions?
IgG
IgM
IgE
IgA
Explanation - IgE binds to allergens and triggers histamine release from mast cells, causing allergic reactions.
Correct answer is: IgE
Q.6 Which antibody can cross the placenta to provide passive immunity to the fetus?
IgM
IgG
IgA
IgE
Explanation - IgG is the only antibody class that can cross the placenta, providing passive immunity to the developing fetus.
Correct answer is: IgG
Q.7 Which immunoglobulin forms pentamers in its secreted form?
IgG
IgM
IgA
IgE
Explanation - Secreted IgM exists as a pentamer, allowing it to bind multiple antigens efficiently during the primary immune response.
Correct answer is: IgM
Q.8 Which region of an antibody interacts with Fc receptors on immune cells?
Variable region
Fab region
Hinge region
Fc region
Explanation - The Fc (Fragment crystallizable) region binds to Fc receptors on immune cells to mediate effector functions like phagocytosis.
Correct answer is: Fc region
Q.9 Which immunoglobulin is critical for defense against parasitic infections?
IgG
IgE
IgA
IgM
Explanation - IgE plays a key role in defense against parasitic infections by activating eosinophils and mast cells.
Correct answer is: IgE
Q.10 Which antibody is mainly responsible for agglutination and complement activation?
IgG
IgM
IgA
IgE
Explanation - IgM, being pentameric, is highly efficient in agglutination and activating the complement system.
Correct answer is: IgM
Q.11 Which immunoglobulin is involved in mucosal immunity and is often dimeric in secretions?
IgG
IgA
IgM
IgE
Explanation - Secretory IgA is dimeric and protects mucosal surfaces by preventing pathogen adherence and invasion.
Correct answer is: IgA
Q.12 Which antibody type is produced in largest quantity during secondary immune responses?
IgM
IgG
IgA
IgE
Explanation - IgG is produced in large quantities during secondary responses, providing faster and stronger immunity.
Correct answer is: IgG
Q.13 Which antibody has the shortest half-life in serum?
IgG
IgM
IgA
IgE
Explanation - IgE has the shortest half-life (~2 days) compared to other immunoglobulins.
Correct answer is: IgE
Q.14 Which of the following antibodies is mainly monomeric in serum but dimeric in secretions?
IgG
IgA
IgM
IgE
Explanation - IgA exists as a monomer in serum and as a dimer in mucosal secretions to provide mucosal immunity.
Correct answer is: IgA
Q.15 Which antibody is key in neutralizing toxins and viruses?
IgG
IgM
IgA
IgE
Explanation - IgG neutralizes toxins and viruses effectively and is important in long-term immunity.
Correct answer is: IgG
Q.16 Which antibody is least abundant in the human body?
IgG
IgM
IgA
IgE
Explanation - IgE is the least abundant in circulation but plays a key role in allergies and parasitic defense.
Correct answer is: IgE
Q.17 Which antibody can activate complement via the classical pathway most efficiently?
IgG
IgM
IgA
IgE
Explanation - IgM is highly efficient at activating the classical complement pathway due to its pentameric structure.
Correct answer is: IgM
Q.18 Which immunoglobulin is predominantly found in external secretions like tears and saliva?
IgG
IgA
IgM
IgE
Explanation - IgA is predominant in external secretions, providing first-line defense at mucosal surfaces.
Correct answer is: IgA
Q.19 Which antibody class has four subclasses in humans?
IgG
IgA
IgM
IgE
Explanation - Human IgG has four subclasses: IgG1, IgG2, IgG3, and IgG4, each with specific functions.
Correct answer is: IgG
Q.20 Which region of an antibody is responsible for effector functions like opsonization?
Variable region
Fab region
Fc region
Hinge region
Explanation - The Fc region interacts with immune cells to mediate effector functions like opsonization and ADCC.
Correct answer is: Fc region
Q.21 Which antibody is particularly effective against encapsulated bacteria?
IgG
IgM
IgA
IgE
Explanation - IgM's pentameric form makes it highly effective in agglutinating and targeting encapsulated bacteria.
Correct answer is: IgM
Q.22 Which antibody is primarily involved in hypersensitivity type I reactions?
IgG
IgM
IgE
IgA
Explanation - IgE binds to allergens and triggers mast cell degranulation in type I hypersensitivity reactions.
Correct answer is: IgE
Q.23 Which antibody is mainly responsible for long-term immunity after vaccination?
IgM
IgG
IgA
IgE
Explanation - IgG is produced in large amounts during secondary responses and provides long-lasting immunity after vaccination.
Correct answer is: IgG
Q.24 Which antibody is secreted in largest amounts during early stages of infection?
IgG
IgM
IgA
IgE
Explanation - IgM is the first antibody produced and is predominant in early stages of infection.
Correct answer is: IgM