Q.1 Which of the following cells is the primary phagocytic cell in the innate immune system?
B lymphocyte
Macrophage
Plasma cell
T helper cell
Explanation - Macrophages are specialized phagocytes that engulf and digest pathogens as part of the innate immune response.
Correct answer is: Macrophage
Q.2 The thymus is primarily responsible for the maturation of which immune cells?
B cells
T cells
Macrophages
Neutrophils
Explanation - The thymus is the central organ where immature T lymphocytes undergo maturation and selection.
Correct answer is: T cells
Q.3 Which organ is considered the primary site of B cell development in humans?
Thymus
Bone marrow
Spleen
Lymph nodes
Explanation - B cells develop and mature in the bone marrow before migrating to peripheral lymphoid organs.
Correct answer is: Bone marrow
Q.4 Which cells act as antigen-presenting cells (APCs)?
T helper cells
Dendritic cells
Natural killer cells
Cytotoxic T cells
Explanation - Dendritic cells process and present antigens to T cells, initiating adaptive immune responses.
Correct answer is: Dendritic cells
Q.5 Which immune organ filters blood and removes old red blood cells?
Spleen
Thymus
Liver
Bone marrow
Explanation - The spleen acts as a blood filter, removing damaged red blood cells and pathogens.
Correct answer is: Spleen
Q.6 Natural killer (NK) cells belong to which part of immunity?
Adaptive immunity
Innate immunity
Humoral immunity
Passive immunity
Explanation - NK cells provide rapid responses to virally infected and tumor cells as part of innate immunity.
Correct answer is: Innate immunity
Q.7 Which cells are responsible for antibody production?
Helper T cells
Plasma cells
Dendritic cells
NK cells
Explanation - Plasma cells are differentiated B cells that secrete antibodies.
Correct answer is: Plasma cells
Q.8 Where are lymphocytes primarily found?
Heart
Pancreas
Lymph nodes
Kidneys
Explanation - Lymph nodes are major secondary lymphoid organs where lymphocytes encounter antigens.
Correct answer is: Lymph nodes
Q.9 Which T cell subset directly kills infected cells?
Cytotoxic T cells
Helper T cells
Regulatory T cells
Memory T cells
Explanation - Cytotoxic T cells (CD8+) destroy virus-infected and cancerous cells.
Correct answer is: Cytotoxic T cells
Q.10 What is the main function of the bone marrow?
Filter blood
Produce immune cells
Store antibodies
Digest pathogens
Explanation - Bone marrow is the site of hematopoiesis, where immune cells originate.
Correct answer is: Produce immune cells
Q.11 Which cells provide long-term immunity after an infection?
Memory cells
NK cells
Neutrophils
Mast cells
Explanation - Memory B and T cells persist long-term to quickly respond to repeat infections.
Correct answer is: Memory cells
Q.12 Which immune cell releases histamine during allergic reactions?
Neutrophil
Macrophage
Mast cell
Plasma cell
Explanation - Mast cells release histamine and other mediators during allergic responses.
Correct answer is: Mast cell
Q.13 Which lymphoid organ atrophies with age?
Spleen
Bone marrow
Thymus
Lymph nodes
Explanation - The thymus shrinks with age, reducing new T cell production.
Correct answer is: Thymus
Q.14 Peyer's patches are found in which part of the body?
Lungs
Small intestine
Skin
Brain
Explanation - Peyer's patches are lymphoid tissues in the small intestine important for gut immunity.
Correct answer is: Small intestine
Q.15 Which cells bridge innate and adaptive immunity by presenting antigens?
Neutrophils
Dendritic cells
NK cells
Eosinophils
Explanation - Dendritic cells present antigens to T cells, linking innate and adaptive immunity.
Correct answer is: Dendritic cells
Q.16 Which type of lymphocyte requires antigen presentation to become activated?
B cells
Cytotoxic T cells
Helper T cells
NK cells
Explanation - Helper T cells require antigen presentation via MHC-II molecules for activation.
Correct answer is: Helper T cells
Q.17 Which immune cells are most abundant in blood?
Eosinophils
Neutrophils
Basophils
Monocytes
Explanation - Neutrophils are the most abundant white blood cells, important for rapid infection response.
Correct answer is: Neutrophils
Q.18 Which organ is the main site for immune responses to antigens in the blood?
Spleen
Thymus
Bone marrow
Lymph node
Explanation - The spleen monitors blood-borne antigens and mounts immune responses.
Correct answer is: Spleen
Q.19 What is the role of regulatory T cells?
Kill infected cells
Produce antibodies
Suppress immune responses
Activate macrophages
Explanation - Regulatory T cells prevent overactive immune responses and maintain tolerance.
Correct answer is: Suppress immune responses
Q.20 Which immune cells target parasites?
Eosinophils
Neutrophils
NK cells
Dendritic cells
Explanation - Eosinophils release toxic granules effective against parasites.
Correct answer is: Eosinophils
Q.21 Where do mature B and T cells encounter antigens?
Primary lymphoid organs
Secondary lymphoid organs
Bone marrow
Thymus
Explanation - Lymph nodes and spleen are secondary organs where lymphocytes interact with antigens.
Correct answer is: Secondary lymphoid organs
Q.22 Which cell type plays a key role in allergic asthma?
Neutrophil
Mast cell
Macrophage
NK cell
Explanation - Mast cells release histamine and mediators contributing to asthma symptoms.
Correct answer is: Mast cell
Q.23 Which lymphoid organ is strategically located at mucosal surfaces?
MALT
Thymus
Bone marrow
Spleen
Explanation - Mucosa-associated lymphoid tissue (MALT) protects mucosal entry points.
Correct answer is: MALT
Q.24 Which immune cells are the first to arrive at infection sites?
Neutrophils
Plasma cells
NK cells
Basophils
Explanation - Neutrophils are rapid responders and the first leukocytes to reach infection sites.
Correct answer is: Neutrophils
Q.25 Which structure connects lymph nodes to allow lymphocyte circulation?
Blood vessels
Lymphatic vessels
Capillaries
Nerves
Explanation - Lymphatic vessels transport lymphocytes and antigens between lymph nodes.
Correct answer is: Lymphatic vessels