Nokea
The rearrangement of gene segments that occurs randomly in B cell receptor genes and T cell receptor genes:
- A. Occurs during clonal expansion of B cells and T cells
- B. Involves rapid genetic mutation after lymphocytes become activated
- C. Allows the mature lymphocyte population to recognize an enormous diversity of antigens
- D. Occurs in the DNA of all cells in the body
Correct Answer: C
Rationale: Step 1: Gene rearrangement in B cell and T cell receptor genes creates unique receptor proteins.
Step 2: This diversity allows mature lymphocytes to recognize a wide range of antigens.
Step 3: This process is crucial for adaptive immune response and antigen specificity.
Step 4: Choices A and B do not accurately describe gene rearrangement.
Step 5: Choice D is incorrect as gene rearrangement is specific to lymphocytes, not all cells in the body.
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Which of the following molecules can function both as complement initiators and as opsonins?
- A. C3b
- B. C-reactive protein
- C. MBL
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D, All of the above. C3b, C-reactive protein, and MBL can all function as complement initiators and opsonins. C3b is a key complement protein involved in both processes. C-reactive protein can activate complement and enhance phagocytosis. MBL can also activate complement and enhance phagocytosis by binding to pathogens. All choices can serve as both initiators of the complement cascade and as opsonins, making D the correct answer.
Which cells play a central role in Type I hypersensitivity reactions?
- A. Neutrophils
- B. Mast cells
- C. Macrophages
- D. Dendritic cells
Correct Answer: B
Rationale: The correct answer is B: Mast cells. Mast cells play a central role in Type I hypersensitivity reactions by releasing histamine, cytokines, and other inflammatory mediators in response to allergens. This triggers the allergic response. Neutrophils (A), Macrophages (C), and Dendritic cells (D) are not central to Type I hypersensitivity reactions. Neutrophils are involved in acute inflammation, macrophages play a role in phagocytosis and antigen presentation, and dendritic cells are important in initiating adaptive immune responses.
Which of the following best describes granuloma formation?
- A. IgE-mediated mast cell activation
- B. Persistent recruitment of macrophages around undigested antigens
- C. Deposition of immune complexes in tissues
- D. Complement-mediated cell lysis
Correct Answer: B
Rationale: Granuloma formation is characterized by the persistent recruitment of macrophages around undigested antigens. Initially, macrophages attempt to phagocytose the antigen but fail to digest it completely, leading to the formation of a granuloma. This process is a protective mechanism to isolate the antigen and prevent its spread. IgE-mediated mast cell activation (choice A) is associated with allergic reactions, not granuloma formation. Deposition of immune complexes in tissues (choice C) is linked to immune complex-mediated diseases, not granuloma formation. Complement-mediated cell lysis (choice D) involves the destruction of target cells by the complement system, which is not directly related to granuloma formation.
Which of the following is not an outcome of phagocytosis in macrophages
- A. Respiratory burst
- B. Nitric oxide production
- C. Antigen presentation
- D. Complement activation
Correct Answer: D
Rationale: The correct answer is D: Complement activation. Phagocytosis by macrophages involves engulfing and digesting pathogens. Complement activation occurs through a separate pathway involving a series of proteins that enhance the immune response. Phagocytosis does not directly lead to complement activation. Choices A, B, and C are outcomes of phagocytosis in macrophages: Respiratory burst involves production of reactive oxygen species, nitric oxide production helps destroy pathogens, and antigen presentation is important for activating other immune cells.
Which immune system function is most relevant to cancer?
- A. Suppressing cytokine release
- B. Promoting adaptive immunity only
- C. Identifying and eliminating abnormal cells
- D. Limiting the effectiveness of phagocytes
Correct Answer: C
Rationale: The correct answer is C: Identifying and eliminating abnormal cells. This function is most relevant to cancer because the immune system's ability to recognize and destroy abnormal cells is crucial in preventing the development and spread of cancer. The immune system constantly surveys the body for cells that have mutated or become cancerous, and when identified, it initiates an immune response to eliminate them. This process is essential for maintaining the body's health and preventing cancerous cells from proliferating.
Choice A (Suppressing cytokine release) is incorrect because cytokines play a role in regulating the immune response, which can be important in cancer immunity. Choice B (Promoting adaptive immunity only) is incorrect as both innate and adaptive immune responses are involved in combating cancer. Choice D (Limiting the effectiveness of phagocytes) is incorrect as phagocytes are important in recognizing and destroying cancer cells.