Nokea
Developing T cells in the thymus can express
- A. Both CD4 and CD8
- B. Only CD4
- C. Only CD8
- D. Neither CD4 or CD8
Correct Answer: A
Rationale: The correct answer is A because developing T cells initially express both CD4 and CD8 co-receptors in the thymus. This stage is crucial for T cell maturation and selection. Eventually, T cells undergo positive and negative selection processes to become either CD4+ helper T cells or CD8+ cytotoxic T cells based on their specificity and function. Choices B and C are incorrect because T cells initially express both CD4 and CD8. Choice D is also incorrect as T cells do express either CD4 or CD8 during their development in the thymus.
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Which of the following is NOT a random event
- A. Genetic recombination of VDJ segments for TCR assembly
- B. Genetic recombination of VDJ segments for BCR assembly
- C. CD4 vs CD8 T cell fate
- D. TH1 differentiation vs TH2 differentiation
Correct Answer: D
Rationale: The correct answer is D, TH1 differentiation vs TH2 differentiation, as it is not a random event. TH1 and TH2 differentiation is determined by cytokine signals, not random chance. A, Genetic recombination of VDJ segments for TCR assembly, and B, Genetic recombination of VDJ segments for BCR assembly, involve random processes during immune cell development. C, CD4 vs CD8 T cell fate, is determined by random rearrangement of gene segments during T cell development. Thus, D is the only choice that does not involve a random event in immune cell development.
Acquired immunity is a result of previous exposure
- A. serious illness
- B. to vaccination
- C. repeated exposure to the same factor
- D. treatment with penicillin
Correct Answer: B
Rationale: The correct answer is B: to vaccination. Acquired immunity is the immune response developed after exposure to a vaccine, which stimulates the immune system to recognize and remember specific pathogens. Vaccination helps the body build immunity without causing serious illness like choice A, without requiring repeated exposure like choice C, and without being related to treatment with penicillin like choice D. Vaccination mimics natural infection, prompting the body to produce memory cells that can respond more effectively when encountering the actual pathogen in the future.
The oxidation-reduction pairs X/XHâ‚‚ and Y/YHâ‚‚ have reduction potentials of -50 and +75 millivolts, respectively. This means that electrons would most likely be removed from ______ to reduce ______.
- A. XHâ‚‚, Y
- B. Y, XHâ‚‚
- C. YHâ‚‚, X
- D. Y, YHâ‚‚
Correct Answer: A
Rationale: The correct answer is A: XHâ‚‚, Y. This is because the reduction potential of -50 mV for X/XHâ‚‚ indicates that X is more likely to lose electrons compared to Y with a reduction potential of +75 mV. Therefore, electrons would be removed from XHâ‚‚ (X) to reduce Y. Choice B is incorrect because Y has a higher reduction potential than XHâ‚‚, so electrons would not be removed from Y to reduce XHâ‚‚. Choices C and D are also incorrect as they do not consider the relative reduction potentials of X/XHâ‚‚ and Y/YHâ‚‚.
What percent of clients with chronic fatigue syndrome (CFS) will experience hypotension during a tilt table test,which can eventually be diagnostic for these clients?
- A. 60%
- B. 96%
- C. 80%
- D. 20%
Correct Answer: B
Rationale: Approximately 96% of clients with CFS experience hypotension during a tilt table test which helps in diagnosing the condition.
What type of antibodies predominate in the secondary immune response?
- A. IgM
- B. IgE
- C. IgG
- D. IgD
Correct Answer: C
Rationale: The correct answer is C: IgG. In the secondary immune response, IgG antibodies predominate due to memory B cells rapidly producing them upon re-exposure to the same antigen. IgG provides long-lasting immunity and is more efficient in neutralizing pathogens. IgM (A) is the primary antibody in the initial immune response. IgE (B) is involved in allergic reactions. IgD (D) functions as a receptor on B cells.