Cellular Immunology — Notes OmpathStudy

Question 1 The ability of an organism to resist infections by the pathogens is called A. Infection B. Hypersensitivity C. Immunity D. Allergy E. Attenuation Answer: C. Immunity Explanation: Immunity is the body's natural defense mechanism against pathogenic microorganisms, toxins, and other harmful substances. --- Question 2 Name the group of pattern recognition molecules which functions exclusively as a signaling receptor A. CRP B. Toll-like receptor C. MBL D. LPS E. MMLS Answer: B. Toll-like receptor Explanation: Toll-like receptors (TLRs) are pattern recognition receptors that recognize PAMPs and function exclusively as signaling receptors. --- Question 3 Name the first cells which are recruited at the place of infection A. NK cells B. Basophils C. Neutrophils D. Macrophages E. A and B Answer: C. Neutrophils Explanation: Neutrophils are the first immune cells to arrive at the site of infection during acute inflammation. --- Question 4 Which of the following antibody gives a primary immune reaction A. IgG B. IgM C. IgA D. IgE E. A and B Answer: B. IgM Explanation: IgM is the first antibody produced during a primary immune response and is most effective at complement activation. --- Question 5 Which of these is NOT a characteristic feature of adaptive immunity A. Immunogenic memory B. Adaptive immunity C. Self/non-self recognition D. Diversity E. None of the above Answer: B. Adaptive immunity Explanation: Adaptive immunity is highly antigen-specific, unlike innate immunity which is non-specific. --- Question 6 The major role of the complement system is to work in conjunction with A. Antibodies to lyse cells via the C8 and C9 components B. Antibodies to lyse cells via the perforin molecules C. Antibodies to opsonize cells D. The major histocompatibility complex for cell recognition E. The T-cell receptor for production of lymphokines Answer: A. Antibodies to lyse cells via the C8 and C9 components Explanation: The complement system works with antibodies to form the membrane attack complex (MAC) using C5b-C9 components. --- Question 7 One principal function of complement is to A. Bind antibodies attached to cell surfaces and to lyse these cells B. Cross-link allergens C. Inactivate perforins D. Mediate the release of histamine E. Phagocytize antigens Answer: A. Bind antibodies attached to cell surfaces and to lyse these cells Explanation: The complement system binds to antibodies on target cells and forms MAC to lyse the cells. --- Question 8 Complement component C3 is cleaved by A. C3bB B. C3bBb C. Factor B D. Factor D E. Factor H Answer: A. C3bB Explanation: C3bBb is the C3 convertase of the alternative pathway that cleaves C3 into C3a and C3b. --- Question 9 The membrane attack complex in the complement pathway consists of A. C3b3b, Bb B. C5b,6,7,8,9 C. Colicins D. OH E. Properdin Answer: B. C5b,6,7,8,9 Explanation: The membrane attack complex (MAC) is formed by complement components C5b, C6, C7, C8, and C9. --- Question 10 Acute inflammation can be initiated by A. An increase in vascular permeability B. C3 C. Influx of neutrophils D. Lysozyme E. Mast cell activation Answer: E. Mast cell activation Explanation: Mast cell activation releases inflammatory mediators like histamine, which initiate acute inflammation. --- Question 11 Clonal selection occurs when antigen is encountered by A. Basophils B. Eosinophils C. Mast cells D. Neutrophils E. Clonal selection Answer: E. Clonal selection Explanation: Clonal selection is the process where specific T cells that recognize a particular antigen are selected for proliferation. --- Question 12 Complement component C3b A. Directly injures bacteria B. Is an anaphylatoxin C. Is chemotactic D. Is the inactive form of C3 E. Opsonizes bacteria Answer: E. Opsonizes bacteria Explanation: C3b is a major opsonin that coats bacteria, marking them for phagocytosis by immune cells. --- Question 13 Naturally acquired active immunity would be most likely acquired through which of the following processes A. Vaccination B. Drinking colostrum C. Natural birth D. Infection with disease-causing organism followed by recovery E. Both A and C Answer: D. Infection with disease-causing organism followed by recovery Explanation: Naturally acquired active immunity occurs when the immune system responds to a natural infection. --- Question 14 Which of the following convey the longest-lasting immunity to an infectious agent A. Naturally acquired passive immunity B. Artificially acquired passive immunity C. Naturally acquired active immunity D. All of these E. None of these Answer: C. Naturally acquired active immunity Explanation: Naturally acquired active immunity provides the longest-lasting protection through memory cell development. --- Question 15 Which of the following substances will not stimulate an immune response unless they are bound to a larger molecule A. Antigen B. Virus C. Hapten D. Mitogen E. Antibody Answer: C. Hapten Explanation: Haptens are small molecules that become immun