Nokea
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.
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Dendritic cells migrating from tissues enter the lymph nodes through
- A. Thoracic duct
- B. HEV
- C. Afferent lymphatics
- D. Efferent lymphatics
Correct Answer: C
Rationale: The correct answer is C: Afferent lymphatics. Dendritic cells migrate from tissues to lymph nodes through afferent lymphatics, which are small vessels that carry lymph into the lymph nodes. Once inside the lymph nodes, dendritic cells interact with T cells to initiate immune responses. The thoracic duct (A) drains lymph from the entire body into the bloodstream, not directly into lymph nodes. High endothelial venules (HEV) (B) are specialized blood vessels in lymph nodes where lymphocytes enter from the bloodstream, not dendritic cells. Efferent lymphatics (D) carry lymph out of the lymph nodes, not into them.
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 of the following statements about innate immunity is TRUE?
- A. It has no role in stimulating adaptive immunity
- B. It requires prior exposure to pathogens to function
- C. It includes both physical and cellular defenses
- D. It is antigen-specific
Correct Answer: C
Rationale: Step 1: Innate immunity is the body's first line of defense against pathogens.
Step 2: Physical defenses include barriers like skin and mucous membranes.
Step 3: Cellular defenses include immune cells like macrophages and natural killer cells.
Step 4: These defenses are present from birth and do not require prior exposure to pathogens.
Step 5: Choice C is true as innate immunity encompasses both physical and cellular defenses, making it the correct answer.
Other choices are incorrect:
A: Innate immunity does play a role in stimulating adaptive immunity through antigen presentation.
B: It does not require prior exposure to function, as it is a rapid and non-specific response.
D: Innate immunity is not antigen-specific; adaptive immunity is responsible for antigen-specific responses.
Ferrets have recently been objects of an intense debate within the scientific community in the field of Flu research because
- A. Of a recent outbreak caused by a novel Influenza strain
- B. Of a recent outbreak caused by a highly virulent H1N1 strain
- C. Mutations have been introduced in H5N1 creating a strain transmissible among these mammals
- D. Two publications on this animal model for Flu were put on hold due to biosecurity reasons
Correct Answer: C
Rationale: The correct answer is C because it indicates a specific reason for the intense debate within the scientific community regarding ferrets in Flu research. Mutations in H5N1 creating a strain transmissible among ferrets is significant as it highlights a potential threat of cross-species transmission and the need for further study.
A is incorrect as it does not provide a specific reason related to ferrets and their role in Flu research. B is incorrect because it focuses on a specific strain (H1N1) rather than mutations in H5N1. D is incorrect as it mentions publications being put on hold but does not address the core issue of mutations and transmissibility among ferrets.
TLRs contain a cytoplasmic TIR domain also found in the receptor of
- A. Type I Interferons
- B. IL-1β
- C. TNF-α
- D. IL-8
Correct Answer: B
Rationale: Step-by-step rationale for Choice B (IL-1β) being correct:
1. The TIR domain is present in Toll-like receptors (TLRs) and IL-1 receptor.
2. TLRs recognize various microbial products, while IL-1 receptor binds IL-1 cytokines.
3. Both TLRs and IL-1 receptor signal through the TIR domain.
4. IL-1β is a cytokine that binds to IL-1 receptor, which contains a TIR domain.
Summary of why the other choices are incorrect:
A: Type I Interferons - Type I interferons signal through JAK-STAT pathway, not TIR domain.
C: TNF-α - TNF receptor family signals through TNF receptor-associated death domain, not TIR domain.
D: IL-8 - IL-8 binds to CXCR1 and CXCR2 receptors, which do not contain a TIR domain.
In summary, Choice B