Nokea
What happens to B cells after clonal selection and expansion?
- A. They produce cytokines
- B. They differentiate into plasma cells to produce antibodies
- C. They initiate phagocytosis
- D. They present antigens to T cells
Correct Answer: B
Rationale: After clonal selection and expansion, B cells differentiate into plasma cells to produce antibodies. This is crucial for the immune response as plasma cells are specialized in antibody production. B cells do not produce cytokines (choice A), initiate phagocytosis (choice C), or present antigens to T cells (choice D) post-clonal selection. Plasma cell differentiation is the key outcome of the B cell activation process, enabling the body to mount an effective immune response against pathogens.
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Which of the following complement components mediate inflammation?
- A. C3b
- B. C3a, C4a, and C5a
- C. C5b
- D. C1q
Correct Answer: B
Rationale: The correct answer is B (C3a, C4a, and C5a) because these complement components are known as anaphylatoxins that mediate inflammation by inducing vasodilation, increasing vascular permeability, and recruiting immune cells. C3b (choice A) is involved in opsonization, not inflammation. C5b (choice C) is part of the membrane attack complex for cell lysis. C1q (choice D) initiates the classical complement pathway, but it does not directly mediate inflammation.
Rolling' of neutrophils on endothelial cells is mediated by:
- A. Selectins expressed on endothelial cells
- B. Integrins expressed on leukocytes
- C. Chemokines such as CXCL-8 (IL-8)
- D. TNF
Correct Answer: A
Rationale: The correct answer is A: Selectins expressed on endothelial cells. Rolling of neutrophils on endothelial cells is a crucial step in the process of inflammation and immune response. Selectins are cell adhesion molecules expressed on endothelial cells that facilitate the initial interaction between leukocytes (such as neutrophils) and endothelial cells. This interaction allows for the rolling of neutrophils along the endothelial surface, which is essential for the subsequent steps of adhesion and transmigration into the tissues. Integrins (Choice B) are involved in the firm adhesion of leukocytes to endothelial cells, not in the initial rolling process. Chemokines (Choice C) such as CXCL-8 are signaling molecules that help in the recruitment of leukocytes but do not directly mediate the rolling process. TNF (Choice D) is a pro-inflammatory cytokine but is not directly involved in the rolling of neutrophils on endothelial cells.
Which cytokine group is most commonly associated with antiviral responses?
- A. Interleukins
- B. Interferons
- C. Tumor necrosis factors
- D. Transforming growth factors
Correct Answer: B
Rationale: Interferons are the correct answer as they are a cytokine group primarily associated with antiviral responses. They play a key role in the immune response against viral infections by inhibiting viral replication and spreading to other cells. Interleukins are more diverse and involved in various immune responses, not specifically antiviral. Tumor necrosis factors are more related to inflammation and cell death. Transforming growth factors are involved in cell growth and differentiation, not primarily antiviral responses. Therefore, B: Interferons is the most appropriate choice for cytokine group associated with antiviral responses.
What is a typical time frame for Type IV hypersensitivity reactions to develop?
- A. Within minutes
- B. 1-3 hours
- C. 24-72 hours
- D. 5-7 days
Correct Answer: C
Rationale: The correct answer is C (24-72 hours) for Type IV hypersensitivity reactions to develop. This type of reaction involves T cell-mediated immune responses, which take time to develop. Initially, sensitization occurs, followed by activation of memory T cells upon re-exposure to the antigen. This process typically takes 24-72 hours to manifest clinically. Choices A (Within minutes), B (1-3 hours), and D (5-7 days) are incorrect because Type IV reactions do not exhibit immediate responses like Type I hypersensitivity reactions (Choice A), nor do they typically take as long as 5-7 days to develop (Choice D). The time frame of 1-3 hours (Choice B) is too short for the characteristic delayed hypersensitivity reaction seen in Type IV responses.
What is the normal range for the hematocrit value in a healthy adult?
- A. 20-40%
- B. 40-60%
- C. 60-80%
- D. 80-100%
Correct Answer: B
Rationale: The correct answer is B: 40-60%. Hematocrit represents the percentage of red blood cells in the blood. The normal range for hematocrit in a healthy adult is typically around 40-60%. Values below 40% may indicate anemia, while values above 60% may suggest conditions like dehydration or polycythemia. Choices A, C, and D are incorrect because they fall outside the normal range for hematocrit levels in a healthy adult.