Nokea
The immunoglobulin class which is the least abundant in the normal adult is
- A. IgG
- B. IgA
- C. IgE
- D. IgD
Correct Answer: C
Rationale: The correct answer is C, IgE. IgE is the least abundant immunoglobulin in the normal adult because it is primarily involved in allergic responses and parasitic infections, leading to its lower baseline levels compared to other classes. IgG is the most abundant and provides long-term immunity. IgA is found in mucosal areas and secretions, crucial for local immunity. IgD functions primarily as a B cell receptor and its levels are relatively low in circulation. Therefore, IgE stands out as the least abundant in the normal adult due to its specialized role in immune responses.
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All of the following are true of antigen EXCEPT which one of the following?
- A. They contain paratopes
- B. They will react with antibodies.
- C. They contain antigenic determinants.
- D. They can elicit an immune response.
Correct Answer: A
Rationale: The correct answer is A. Paratopes are actually parts of antibodies that bind to antigens, not the antigens themselves. A is incorrect because antigens do not contain paratopes; rather, they contain epitopes or antigenic determinants that are recognized by antibodies. B, C, and D are true statements about antigens. B is true because antigens react with antibodies. C is true because antigens contain antigenic determinants that antibodies recognize. D is true because antigens can elicit an immune response by stimulating the production of antibodies. Therefore, the correct answer is A because antigens do not contain paratopes.
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.
Which T lymphocytes are involved in direct attack and destruction of foreign pathogens?
- A. Dendritic cells
- B. Natural killer cells
- C. T helper (CD4) cells
- D. T cytotoxic (CD8) cells
Correct Answer: D
Rationale: T cytotoxic (CD8) cells directly attack and destroy infected or abnormal cells, making them crucial for eliminating pathogens.
Which of the following statements is NOT true?
- A. B cells are important in the defense against extracellular pathogens
- B. The number of memory B cells recognizing antigen X is always smaller than the number of naïve B cells recognizing antigen X, as most specific B cells are killed when the immune response subsides
- C. Memory B cells are B cells differentiated from cells that have encountered the antigen and are long-lived
- D. The B cell repertoire is virtually infinite and includes specificities for any possible antigen
Correct Answer: B
Rationale: The correct answer is B because the statement is false. Memory B cells are formed during an immune response and persist long-term, allowing for a faster and more robust response upon reinfection with the same antigen. The number of memory B cells recognizing an antigen is typically greater than the number of naïve B cells, as they are specifically primed and preserved. In contrast, naïve B cells are naive to the antigen and need to undergo activation and differentiation upon encountering the antigen for the first time. Therefore, statement B is incorrect as it inaccurately suggests that memory B cells are always fewer than naïve B cells recognizing the same antigen.
CD3 is a complex of proteins involved in
- A. Antigen binding
- B. Signal propagation in T cells
- C. Signal propagation in B cells
- D. T cell homing to lymph nodes
Correct Answer: B
Rationale: The correct answer is B: Signal propagation in T cells. CD3 is a protein complex found on the surface of T cells that is crucial for T cell receptor signaling and activation. It helps propagate signals within T cells, leading to T cell activation and immune responses. Choice A (Antigen binding) is incorrect as CD3 is not directly involved in antigen binding. Choice C (Signal propagation in B cells) is incorrect as CD3 is specific to T cells, not B cells. Choice D (T cell homing to lymph nodes) is incorrect as CD3 is not responsible for the physical migration of T cells to lymph nodes.