Nokea
The epitopes recognized by T cells are always:
- A. Conformational
- B. Linear
- C. On the antigen surface
- D. Buried inside the antigen
Correct Answer: B
Rationale: The correct answer is B: Linear. T cells recognize linear epitopes, which are sequences of amino acids displayed in a linear fashion on the antigen's surface. This recognition occurs through the T cell receptor binding to the linear epitope. Conformational epitopes (A) involve multiple amino acid residues brought together in a specific three-dimensional structure. Epitopes on the antigen surface (C) are correct, but not all T cell epitopes are necessarily on the surface. Epitopes buried inside the antigen (D) are not accessible to T cell receptors for recognition. Thus, the correct choice is B due to the linear presentation of epitopes for T cell recognition.
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How does interferon help the body’s natural defenses?
- A. Directly attacks and destroys virus-infected cells
- B. Augments the immune response by activating phagocytes
- C. Induces production of antiviral proteins in cells that prevent viral replication
- D. Is produced by viral infected cells and prevents the transmission of the virus to adjacent cells
Correct Answer: C
Rationale: Interferons induce the production of antiviral proteins in uninfected cells, preventing viral replication and spread.
Which hypersensitivity type is mediated by T cells?
- A. Type I
- B. Type II
- C. Type III
- D. Type IV
Correct Answer: D
Rationale: The correct answer is D: Type IV hypersensitivity. This type is mediated by T cells, specifically CD4+ helper T cells and CD8+ cytotoxic T cells. The process involves antigen-presenting cells activating T cells, leading to a delayed response. Choices A, B, and C involve different mechanisms and are not mediated by T cells. Type I is mediated by IgE antibodies, Type II involves antibody-mediated cell destruction, and Type III involves immune complex deposition. Therefore, Type IV is the only hypersensitivity type directly mediated by T cells.
A major antibody-mediated mechanism of defense against parasitic worms involves:
- A. Neutrophil degranulation
- B. Opsonization
- C. Triggering of physiological responses (such as coughing) that expel the worm
- D. Neutralization by IgE along the mucosal surface of the gut
Correct Answer: D
Rationale: The correct answer is D because neutralization by IgE along the mucosal surface of the gut is a major antibody-mediated mechanism against parasitic worms. IgE binds to antigens on the worm's surface, leading to the release of histamine and other mediators that help expel the worm. Neutrophil degranulation (A) is more associated with bacterial infections, opsonization (B) is mainly for phagocytosis of pathogens, and triggering physiological responses (C) is not a direct antibody-mediated defense against parasitic worms.
A cytokine essential for clonal expansion of T cells is
- A. IL-1
- B. IL-2
- C. IL4
- D. IL-5
Correct Answer: B
Rationale: The correct answer is B: IL-2. IL-2 is essential for the clonal expansion of T cells as it promotes T cell proliferation. It is produced by activated T cells themselves and plays a crucial role in regulating immune responses. IL-1 is involved in inflammation, not T cell expansion. IL-4 is important for Th2 cell differentiation, while IL-5 is critical for eosinophil activation. In summary, IL-2 specifically promotes T cell clonal expansion, making it the correct choice in this context.
The earliest event of an inflammatory response is
- A. Release of chemokines
- B. Recruitment of neutrophils
- C. Activation of adaptive immunity
- D. Activation of TLRs
Correct Answer: D
Rationale: The correct answer is D: Activation of TLRs. The earliest event in an inflammatory response is the activation of Toll-like receptors (TLRs) by recognizing pathogen-associated molecular patterns (PAMPs). This triggers a signaling cascade leading to the release of pro-inflammatory cytokines and chemokines, which then recruit neutrophils to the site of infection. Activation of adaptive immunity (choice C) occurs later in the immune response, as it involves the activation of T and B cells. While chemokines (choice A) are involved in recruiting immune cells, their release is a consequence of TLR activation. Neutrophils (choice B) are recruited after the release of chemokines.