Q.1 Which of the following cells are primarily responsible for antibody production?
T cells
B cells
Macrophages
Neutrophils
Explanation - B cells differentiate into plasma cells that produce antibodies in response to antigens.
Correct answer is: B cells
Q.2 Which type of immunity is acquired naturally when an individual recovers from an infection?
Active natural immunity
Passive natural immunity
Active artificial immunity
Passive artificial immunity
Explanation - Active natural immunity occurs when the body produces its own antibodies after being exposed to a pathogen.
Correct answer is: Active natural immunity
Q.3 The primary lymphoid organs in humans are:
Spleen and lymph nodes
Thymus and bone marrow
Tonsils and appendix
Liver and kidney
Explanation - Primary lymphoid organs are where lymphocytes are formed and mature: bone marrow for B cells and thymus for T cells.
Correct answer is: Thymus and bone marrow
Q.4 Which immunoglobulin is most abundant in the human serum?
IgA
IgD
IgE
IgG
Explanation - IgG is the most abundant antibody in serum and is responsible for long-term immunity.
Correct answer is: IgG
Q.5 Which of the following is a primary function of macrophages?
Producing antibodies
Phagocytosis of pathogens
Killing virus-infected cells
Secreting histamine
Explanation - Macrophages engulf and digest pathogens, cell debris, and foreign particles through phagocytosis.
Correct answer is: Phagocytosis of pathogens
Q.6 Which cytokine is mainly involved in inducing fever during infection?
Interleukin-1 (IL-1)
Interleukin-2 (IL-2)
Tumor necrosis factor beta (TNF-β)
Interferon-gamma (IFN-γ)
Explanation - IL-1, produced by activated macrophages, acts on the hypothalamus to induce fever.
Correct answer is: Interleukin-1 (IL-1)
Q.7 Which of the following is an example of passive immunity?
Vaccination
Injection of antiserum
Recovery from infection
Exposure to pathogen
Explanation - Passive immunity involves transfer of preformed antibodies, e.g., via antiserum or maternal antibodies.
Correct answer is: Injection of antiserum
Q.8 Which cells are responsible for cell-mediated immunity?
B cells
T cells
Macrophages
Dendritic cells
Explanation - T cells, especially cytotoxic T lymphocytes, mediate cell-mediated immunity by directly killing infected cells.
Correct answer is: T cells
Q.9 The principle of vaccination is based on which type of immunity?
Innate immunity
Passive immunity
Active immunity
Herd immunity
Explanation - Vaccination stimulates the body to produce its own antibodies and memory cells, which is active immunity.
Correct answer is: Active immunity
Q.10 Which of the following is NOT a component of the innate immune system?
Skin
Phagocytes
Complement proteins
Antibodies
Explanation - Innate immunity is non-specific and present at birth, while antibodies are part of adaptive immunity.
Correct answer is: Antibodies
Q.11 Which part of an antibody molecule determines its class?
Fab region
Fc region
Hinge region
Variable region
Explanation - The Fc (constant) region of an antibody determines its class (IgG, IgA, IgM, etc.) and function.
Correct answer is: Fc region
Q.12 Which of the following diseases is caused by an autoimmune response?
Diabetes mellitus type 1
Influenza
Tuberculosis
Malaria
Explanation - Type 1 diabetes occurs when the immune system attacks pancreatic beta cells, making it autoimmune.
Correct answer is: Diabetes mellitus type 1
Q.13 Which organ is responsible for filtering pathogens from the blood?
Liver
Spleen
Kidney
Pancreas
Explanation - The spleen filters blood, removes old RBCs, and traps pathogens for immune response.
Correct answer is: Spleen
Q.14 Which antibody is primarily found in mucosal surfaces like the respiratory tract?
IgG
IgA
IgM
IgE
Explanation - IgA is secreted in mucus, saliva, and tears to protect mucosal surfaces from infection.
Correct answer is: IgA
Q.15 Which type of hypersensitivity reaction involves IgE antibodies and histamine release?
Type I
Type II
Type III
Type IV
Explanation - Type I hypersensitivity is immediate and involves IgE-mediated mast cell degranulation releasing histamine.
Correct answer is: Type I
Q.16 Complement proteins primarily function to:
Directly kill bacteria
Produce antibodies
Stimulate red blood cell formation
Inhibit T cell activation
Explanation - Complement proteins enhance phagocytosis, inflammation, and can form membrane attack complexes to lyse pathogens.
Correct answer is: Directly kill bacteria
Q.17 Which vaccine type uses a weakened form of the pathogen?
Inactivated vaccine
Live attenuated vaccine
Subunit vaccine
Toxoid vaccine
Explanation - Live attenuated vaccines use weakened pathogens that can replicate but do not cause disease, eliciting strong immunity.
Correct answer is: Live attenuated vaccine
Q.18 Which of the following is a characteristic of adaptive immunity?
Non-specific response
Immediate response
Memory formation
Barrier protection
Explanation - Adaptive immunity is specific and involves memory cells that allow faster response upon re-exposure to the pathogen.
Correct answer is: Memory formation
Q.19 Which T cell subtype directly kills virus-infected cells?
Helper T cells
Cytotoxic T cells
Regulatory T cells
Memory T cells
Explanation - Cytotoxic T cells (CD8+) recognize and destroy infected or abnormal cells via perforin and granzymes.
Correct answer is: Cytotoxic T cells
Q.20 Which of the following is NOT a typical symptom of inflammation?
Redness
Swelling
Fever
Pallor
Explanation - Inflammation is characterized by redness, heat, swelling, and pain; pallor is not a typical symptom.
Correct answer is: Pallor
Q.21 Which of the following is an example of a secondary lymphoid organ?
Bone marrow
Thymus
Lymph node
Red bone marrow
Explanation - Secondary lymphoid organs like lymph nodes and spleen are sites where immune responses are initiated.
Correct answer is: Lymph node
Q.22 Which cell type acts as an antigen-presenting cell (APC) to T cells?
Erythrocytes
Neutrophils
Dendritic cells
Platelets
Explanation - Dendritic cells process antigens and present them on MHC molecules to T cells to initiate adaptive immunity.
Correct answer is: Dendritic cells
Q.23 Which disease is caused by a deficiency in B cells?
Severe combined immunodeficiency (SCID)
X-linked agammaglobulinemia
Hodgkin's lymphoma
Leukemia
Explanation - X-linked agammaglobulinemia results from B cell deficiency, leading to low antibody production and recurrent infections.
Correct answer is: X-linked agammaglobulinemia
Q.24 Which of the following best describes herd immunity?
Immunity of an individual after vaccination
Population-level protection due to high immunity
Temporary immunity after infection
Artificial immunity through serum injection
Explanation - Herd immunity occurs when a large portion of the population is immune, indirectly protecting those who are susceptible.
Correct answer is: Population-level protection due to high immunity
Q.25 Which of the following is a key function of helper T cells (CD4+)?
Killing infected cells
Activating B cells and macrophages
Producing antibodies
Phagocytosis of pathogens
Explanation - Helper T cells coordinate immune responses by activating B cells to produce antibodies and macrophages to enhance phagocytosis.
Correct answer is: Activating B cells and macrophages
Q.26 Which of the following cells are primarily responsible for producing antibodies?
T lymphocytes
B lymphocytes
Macrophages
Neutrophils
Explanation - B lymphocytes, when activated by antigens, differentiate into plasma cells that produce antibodies.
Correct answer is: B lymphocytes
Q.27 Which immunoglobulin is most abundant in human serum?
IgA
IgD
IgE
IgG
Explanation - IgG constitutes approximately 75-80% of serum antibodies and provides long-term immunity.
Correct answer is: IgG
Q.28 Which type of immunity is mediated by T lymphocytes without antibodies?
Humoral immunity
Cell-mediated immunity
Innate immunity
Passive immunity
Explanation - Cell-mediated immunity is orchestrated by T cells that destroy infected cells or coordinate immune responses.
Correct answer is: Cell-mediated immunity
Q.29 The primary lymphoid organs include:
Spleen and lymph nodes
Bone marrow and thymus
Tonsils and Peyer's patches
Appendix and spleen
Explanation - Primary lymphoid organs are where lymphocytes mature. B cells mature in bone marrow, T cells in the thymus.
Correct answer is: Bone marrow and thymus
Q.30 Which of the following is NOT a component of the innate immune system?
Macrophages
Natural killer cells
Complement system
Plasma cells
Explanation - Plasma cells are part of the adaptive immune system; innate immunity includes cells like macrophages and NK cells.
Correct answer is: Plasma cells
Q.31 Which cytokine is mainly responsible for inducing fever during infection?
Interleukin-1 (IL-1)
Interleukin-4 (IL-4)
Tumor necrosis factor beta (TNF-β)
Interferon gamma (IFN-γ)
Explanation - IL-1 is a pro-inflammatory cytokine that acts on the hypothalamus to induce fever.
Correct answer is: Interleukin-1 (IL-1)
Q.32 Which antibody class is mainly present in mucosal surfaces?
IgA
IgG
IgM
IgE
Explanation - IgA is secreted in mucosal surfaces like respiratory and intestinal tracts and provides local immunity.
Correct answer is: IgA
Q.33 Which of the following is an example of passive immunity?
Vaccination with inactivated polio virus
Maternal antibodies in newborn
Recovery from chickenpox
Exposure to a pathogen
Explanation - Passive immunity involves the transfer of pre-formed antibodies, such as from mother to child through placenta or breast milk.
Correct answer is: Maternal antibodies in newborn
Q.34 Major histocompatibility complex (MHC) molecules present antigens to:
B cells
T cells
Neutrophils
Macrophages
Explanation - MHC molecules on antigen-presenting cells display processed antigens to T lymphocytes to initiate immune responses.
Correct answer is: T cells
Q.35 Which of the following is a secondary lymphoid organ?
Thymus
Bone marrow
Spleen
Red marrow
Explanation - Secondary lymphoid organs are sites where lymphocytes encounter antigens. Spleen and lymph nodes are examples.
Correct answer is: Spleen
Q.36 Which immune cells form the first line of defense against viral infections?
Neutrophils
Natural killer cells
B lymphocytes
Eosinophils
Explanation - NK cells can detect and destroy virus-infected cells without prior sensitization.
Correct answer is: Natural killer cells
Q.37 Which antibody is primarily involved in allergic reactions?
IgA
IgD
IgE
IgG
Explanation - IgE binds to allergens and triggers release of histamine from mast cells, leading to allergy symptoms.
Correct answer is: IgE
Q.38 Which of the following is NOT a function of the complement system?
Opsonization
Cell lysis
Antibody production
Chemotaxis
Explanation - Complement system aids in opsonization, cell lysis, and chemotaxis, but does not produce antibodies.
Correct answer is: Antibody production
Q.39 Which disease is caused by a deficiency of vitamin C affecting immunity?
Scurvy
Rickets
Beriberi
Pellagra
Explanation - Vitamin C deficiency leads to scurvy, which impairs collagen formation and weakens immunity.
Correct answer is: Scurvy
Q.40 Which of the following cells acts as a professional antigen-presenting cell (APC)?
Macrophages
Erythrocytes
Platelets
Fibroblasts
Explanation - Macrophages, dendritic cells, and B cells act as APCs that process and present antigens to T cells.
Correct answer is: Macrophages
Q.41 Which of the following vaccines is a live attenuated vaccine?
BCG
Tetanus toxoid
Hepatitis B
Rabies (inactivated)
Explanation - BCG vaccine contains a live, attenuated strain of Mycobacterium bovis to confer immunity against tuberculosis.
Correct answer is: BCG
Q.42 Which immune cells are involved in graft rejection?
Neutrophils
T lymphocytes
Eosinophils
Basophils
Explanation - T cells recognize foreign MHC molecules on transplanted tissues and mediate graft rejection.
Correct answer is: T lymphocytes
Q.43 Which of the following is NOT a symptom of inflammation?
Redness
Heat
Loss of function
Hypotension
Explanation - Classic signs of inflammation are redness, heat, swelling, pain, and loss of function. Hypotension is unrelated.
Correct answer is: Hypotension
Q.44 Which of the following pathogens is recognized by Toll-like receptors (TLRs) in innate immunity?
Bacterial lipopolysaccharides
Glucose molecules
DNA polymerase
Hemoglobin
Explanation - TLRs detect pathogen-associated molecular patterns such as LPS from bacterial cell walls to trigger immune responses.
Correct answer is: Bacterial lipopolysaccharides
Q.45 Which of the following is a characteristic of adaptive immunity?
Immediate response
Memory response
Non-specific
Barrier defense
Explanation - Adaptive immunity is specific to antigens and can generate immunological memory for faster future responses.
Correct answer is: Memory response
Q.46 Which of the following is a major cause of immunodeficiency?
HIV infection
Influenza virus
Tetanus toxin
Vitamin D overdose
Explanation - HIV targets CD4+ T cells leading to immunodeficiency and increased susceptibility to opportunistic infections.
Correct answer is: HIV infection
Q.47 Which type of hypersensitivity reaction is immediate and IgE mediated?
Type I
Type II
Type III
Type IV
Explanation - Type I hypersensitivity reactions are rapid, IgE-mediated, and include allergies, anaphylaxis, and asthma.
Correct answer is: Type I
Q.48 Which organ removes aged and damaged red blood cells and also participates in immune response?
Liver
Spleen
Kidney
Pancreas
Explanation - The spleen filters blood, removes aged RBCs, and provides a site for immune responses against blood-borne antigens.
Correct answer is: Spleen
Q.49 Which of the following molecules serves as a chemotactic factor for neutrophils?
Histamine
C3a and C5a
IgG
IL-10
Explanation - Complement components C3a and C5a act as chemotactic factors attracting neutrophils to sites of infection.
Correct answer is: C3a and C5a
Q.50 Which type of immunity is acquired by exposure to a disease and recovery?
Innate immunity
Artificial passive immunity
Natural active immunity
Artificial active immunity
Explanation - Natural active immunity is developed when the body encounters a pathogen naturally and produces its own antibodies.
Correct answer is: Natural active immunity