Q.1 Which of the following cells is primarily responsible for antibody production?
T lymphocytes
B lymphocytes
Macrophages
Neutrophils
Explanation - B lymphocytes differentiate into plasma cells that secrete antibodies specific to antigens.
Correct answer is: B lymphocytes
Q.2 What is the main function of helper T cells (CD4+) in the immune system?
Kill virus-infected cells
Activate B cells and cytotoxic T cells
Phagocytose pathogens
Produce histamine
Explanation - Helper T cells recognize antigens presented by antigen-presenting cells and stimulate B cells and cytotoxic T cells.
Correct answer is: Activate B cells and cytotoxic T cells
Q.3 Which immunoglobulin is most abundant in the serum?
IgA
IgG
IgM
IgE
Explanation - IgG is the most abundant antibody in the blood and extracellular fluid, providing long-term immunity.
Correct answer is: IgG
Q.4 Which of the following is a primary lymphoid organ?
Spleen
Lymph node
Bone marrow
Tonsils
Explanation - Primary lymphoid organs, such as bone marrow and thymus, are sites where lymphocytes develop and mature.
Correct answer is: Bone marrow
Q.5 Which complement pathway is activated by antigen-antibody complexes?
Classical pathway
Alternative pathway
Lectin pathway
Inflammatory pathway
Explanation - The classical complement pathway is triggered when antibodies bind to antigens on a pathogen surface.
Correct answer is: Classical pathway
Q.6 Which type of immunity is mediated by T lymphocytes without antibodies?
Humoral immunity
Cell-mediated immunity
Innate immunity
Passive immunity
Explanation - Cell-mediated immunity involves T cells directly attacking infected or abnormal cells without antibody involvement.
Correct answer is: Cell-mediated immunity
Q.7 Which cytokine is primarily responsible for inducing fever?
Interleukin-1 (IL-1)
Interferon-gamma (IFN-γ)
Tumor necrosis factor-beta (TNF-β)
Transforming growth factor-beta (TGF-β)
Explanation - IL-1 is produced by macrophages and stimulates the hypothalamus to raise body temperature during infection.
Correct answer is: Interleukin-1 (IL-1)
Q.8 Which antibody class is mainly found in mucosal surfaces?
IgG
IgA
IgM
IgE
Explanation - IgA is secreted across mucosal surfaces like the gut, respiratory tract, and saliva, providing local immunity.
Correct answer is: IgA
Q.9 Which cells act as antigen-presenting cells to T cells?
Neutrophils
Macrophages
Red blood cells
Platelets
Explanation - Macrophages process and present antigens on MHC molecules to helper T cells to initiate adaptive immune responses.
Correct answer is: Macrophages
Q.10 Which of the following is NOT a feature of innate immunity?
Immediate response
Specific antigen recognition
Physical barriers
Phagocytosis
Explanation - Innate immunity is nonspecific and provides the first line of defense, unlike adaptive immunity which recognizes specific antigens.
Correct answer is: Specific antigen recognition
Q.11 Which immune cell is primarily responsible for allergic reactions?
Neutrophils
Basophils
Eosinophils
Mast cells
Explanation - Mast cells release histamine and other mediators when IgE antibodies bind to allergens, causing allergic symptoms.
Correct answer is: Mast cells
Q.12 Which receptor on T cells recognizes antigen-MHC complexes?
T-cell receptor (TCR)
B-cell receptor (BCR)
CD8 co-receptor
Fc receptor
Explanation - TCRs bind to antigen fragments presented on MHC molecules, enabling T cells to respond to specific antigens.
Correct answer is: T-cell receptor (TCR)
Q.13 Which antibody is first produced in response to a new infection?
IgG
IgM
IgA
IgE
Explanation - IgM is the primary antibody produced during the initial immune response and forms pentamers to efficiently bind antigens.
Correct answer is: IgM
Q.14 Which molecule is considered a major histocompatibility complex (MHC) class II molecule?
HLA-A
HLA-B
HLA-DR
CD8
Explanation - MHC class II molecules, such as HLA-DR, present antigens to CD4+ helper T cells.
Correct answer is: HLA-DR
Q.15 Which of the following is a type of passive immunity?
Vaccination
Maternal antibodies via breast milk
Recovery from infection
Exposure to pathogens
Explanation - Passive immunity involves the transfer of preformed antibodies from one individual to another, such as from mother to infant.
Correct answer is: Maternal antibodies via breast milk
Q.16 Which immune cells kill virus-infected cells and tumor cells directly?
Helper T cells
Cytotoxic T cells
B cells
Macrophages
Explanation - Cytotoxic T cells (CD8+) recognize antigens presented by MHC I and induce apoptosis in infected or abnormal cells.
Correct answer is: Cytotoxic T cells
Q.17 Which type of hypersensitivity reaction involves IgE and mast cells?
Type I
Type II
Type III
Type IV
Explanation - Type I hypersensitivity is immediate and mediated by IgE antibodies, causing allergies and anaphylaxis.
Correct answer is: Type I
Q.18 Which part of the antibody binds to the antigen?
Fc region
Fab region
Hinge region
Constant region
Explanation - The Fab region of an antibody contains the variable region that specifically binds to antigens.
Correct answer is: Fab region
Q.19 Which of the following cells are professional antigen-presenting cells (APCs)?
Macrophages, B cells, Dendritic cells
Neutrophils, Eosinophils, Basophils
T cells, NK cells, Mast cells
Red blood cells, Platelets, Endothelial cells
Explanation - Professional APCs can process and present antigens to helper T cells to initiate adaptive immunity.
Correct answer is: Macrophages, B cells, Dendritic cells
Q.20 Which cytokine is produced by Th1 cells to activate macrophages?
IL-4
IL-10
IFN-gamma
TNF-alpha
Explanation - Th1 cells secrete IFN-gamma, which enhances the microbicidal activity of macrophages.
Correct answer is: IFN-gamma
Q.21 Which immune mechanism is primarily responsible for transplant rejection?
Innate immunity
Cell-mediated immunity
Humoral immunity
Passive immunity
Explanation - T cells recognize foreign MHC molecules in transplanted tissues and trigger rejection via cytotoxicity.
Correct answer is: Cell-mediated immunity
Q.22 Which immune cell is mainly involved in controlling parasitic infections?
Neutrophils
Eosinophils
B cells
Cytotoxic T cells
Explanation - Eosinophils release toxic granules and mediators that target multicellular parasites like helminths.
Correct answer is: Eosinophils
Q.23 Which of the following best describes the function of natural killer (NK) cells?
Produce antibodies
Present antigens
Kill virus-infected and tumor cells
Activate B cells
Explanation - NK cells are part of innate immunity and can induce apoptosis in infected or abnormal cells without prior sensitization.
Correct answer is: Kill virus-infected and tumor cells
Q.24 Which of the following is a feature of adaptive immunity?
Immediate response
Memory response
Physical barriers
Inflammation
Explanation - Adaptive immunity is characterized by specificity and memory, providing stronger responses upon subsequent exposures to the same antigen.
Correct answer is: Memory response