Q.1 Which of the following is considered the first line of defense in innate immunity?
Skin and mucous membranes
T cells
B cells
Cytokines
Explanation - The skin and mucous membranes act as physical and chemical barriers, forming the first line of defense in innate immunity.
Correct answer is: Skin and mucous membranes
Q.2 Which cell type is primarily responsible for phagocytosis in innate immunity?
Neutrophils
T helper cells
B lymphocytes
Natural killer cells
Explanation - Neutrophils are the most abundant white blood cells and are highly efficient phagocytes that engulf and destroy pathogens.
Correct answer is: Neutrophils
Q.3 Which of the following is NOT a feature of innate immunity?
Immediate response
Non-specific recognition
Memory formation
Physical barriers
Explanation - Innate immunity lacks immunological memory, which is a key feature of adaptive immunity.
Correct answer is: Memory formation
Q.4 Toll-like receptors (TLRs) recognize which type of molecules?
Pathogen-associated molecular patterns
Antibodies
Cytokines
Major histocompatibility molecules
Explanation - TLRs detect pathogen-associated molecular patterns (PAMPs) to trigger innate immune responses.
Correct answer is: Pathogen-associated molecular patterns
Q.5 Which innate immune cell kills virus-infected cells directly without prior sensitization?
Natural killer cells
Cytotoxic T cells
Dendritic cells
Macrophages
Explanation - NK cells recognize stressed or infected cells and kill them without prior antigen exposure.
Correct answer is: Natural killer cells
Q.6 Which soluble factor is part of innate immunity?
Complement proteins
Immunoglobulin G
T cell receptor
MHC class II
Explanation - Complement proteins are innate soluble factors that help opsonize pathogens and promote inflammation.
Correct answer is: Complement proteins
Q.7 Defensins are:
Antimicrobial peptides
Cytokines
Cell adhesion molecules
Enzymes that degrade DNA
Explanation - Defensins are small antimicrobial peptides that disrupt microbial membranes.
Correct answer is: Antimicrobial peptides
Q.8 Which cell bridges innate and adaptive immunity by presenting antigens?
Dendritic cells
Basophils
Neutrophils
NK cells
Explanation - Dendritic cells are antigen-presenting cells that link innate sensing with adaptive responses.
Correct answer is: Dendritic cells
Q.9 Which of the following is a primary function of macrophages?
Phagocytosis
Antibody production
Cytotoxic activity
Histamine release
Explanation - Macrophages engulf and destroy pathogens and present antigens to T cells.
Correct answer is: Phagocytosis
Q.10 Which cytokine is most important for inducing fever during innate responses?
IL-1
IL-2
IL-4
IL-10
Explanation - IL-1 is a pyrogenic cytokine that induces fever as part of the innate immune response.
Correct answer is: IL-1
Q.11 The complement system can be activated by which pathway in innate immunity?
Classical pathway
Lectin pathway
Alternative pathway
All of the above
Explanation - Complement activation occurs via classical, lectin, or alternative pathways in innate defense.
Correct answer is: All of the above
Q.12 Which innate immune cell releases histamine during allergic responses?
Mast cells
Neutrophils
Dendritic cells
NK cells
Explanation - Mast cells release histamine and other mediators in innate and allergic responses.
Correct answer is: Mast cells
Q.13 Which organ is most important for producing innate immune cells?
Bone marrow
Liver
Spleen
Thymus
Explanation - Bone marrow is the site of hematopoiesis, producing innate immune cells such as neutrophils and macrophages.
Correct answer is: Bone marrow
Q.14 Which enzyme in tears and saliva contributes to innate immunity?
Lysozyme
Amylase
Lipase
Pepsin
Explanation - Lysozyme hydrolyzes bacterial cell walls, providing antimicrobial defense.
Correct answer is: Lysozyme
Q.15 Pattern recognition receptors (PRRs) detect:
PAMPs
Antibodies
MHC molecules
Cytotoxic T cells
Explanation - PRRs identify pathogen-associated molecular patterns to initiate innate responses.
Correct answer is: PAMPs
Q.16 Which innate defense mechanism involves restricting free iron to inhibit bacterial growth?
Lactoferrin activity
Lysozyme activity
Complement activation
Antibody binding
Explanation - Lactoferrin binds iron, making it unavailable to bacteria and limiting their growth.
Correct answer is: Lactoferrin activity
Q.17 Which of the following cells can act as both phagocytes and antigen-presenting cells?
Macrophages
NK cells
Basophils
Mast cells
Explanation - Macrophages ingest pathogens and present antigens to T cells.
Correct answer is: Macrophages
Q.18 Interferons primarily protect against which type of pathogens?
Viruses
Bacteria
Fungi
Parasites
Explanation - Interferons are antiviral cytokines that interfere with viral replication.
Correct answer is: Viruses
Q.19 Which innate immune cell forms extracellular traps (NETs) against pathogens?
Neutrophils
NK cells
Macrophages
Eosinophils
Explanation - Neutrophils release extracellular traps (NETs) composed of DNA to trap and kill microbes.
Correct answer is: Neutrophils
Q.20 Which organ filters blood and contributes to innate immune defense?
Spleen
Liver
Thymus
Pancreas
Explanation - The spleen filters pathogens from the blood and supports innate and adaptive immunity.
Correct answer is: Spleen
Q.21 What role do basophils play in innate immunity?
Release inflammatory mediators
Phagocytosis
Antibody production
Antigen presentation
Explanation - Basophils release histamine and other mediators, contributing to inflammation.
Correct answer is: Release inflammatory mediators
Q.22 Which complement fragment acts as an opsonin?
C3b
C5a
C9
C1q
Explanation - C3b coats pathogens, enhancing their recognition and ingestion by phagocytes.
Correct answer is: C3b
Q.23 Which of the following innate immune responses is immediate?
Inflammation
Antibody production
Memory cell activation
Cytotoxic T cell response
Explanation - Inflammation is an immediate innate response to infection or injury.
Correct answer is: Inflammation
Q.24 Which type of immunity do newborns primarily rely on before developing adaptive responses?
Innate immunity
Cell-mediated immunity
Humoral immunity
Passive immunity
Explanation - Newborns depend heavily on innate immunity until their adaptive immune system matures.
Correct answer is: Innate immunity
Q.25 Which acute phase protein increases during innate immune responses?
C-reactive protein
Albumin
Hemoglobin
Troponin
Explanation - C-reactive protein (CRP) is an acute phase reactant that enhances innate immune defense.
Correct answer is: C-reactive protein