Which of the following is NOT a random event

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.

Correct Answer: D

Rationale: Step 1: HIV is a retrovirus because it contains RNA as its genetic material and uses the enzyme reverse transcriptase to convert its RNA into DNA. Step 2: HIV is an RNA virus because its genetic material is RNA. Step 3: HIV is a lentivirus which is a subgroup of retroviruses known for causing slow-progressing diseases. Therefore, the correct answer is D as all statements A, B, and C are true based on the characteristics of HIV.

Correct Answer: B

Rationale: The correct answer is B: Infectious diseases. The immune system's main function is to protect the body from foreign invaders such as bacteria, viruses, and parasites. It recognizes and eliminates these pathogens to prevent infections. Autoimmune diseases (A) occur when the immune system mistakenly attacks healthy cells. Neurological disorders (C) and cardiovascular diseases (D) are not primarily defended against by the immune system as they are not caused by external pathogens.

Correct Answer: C

Rationale: The correct answer is C because adaptive immunity involves T and B lymphocytes that provide specific immune responses tailored to particular pathogens. T and B lymphocytes are key players in adaptive immunity, recognizing and targeting specific antigens. Choice A is incorrect because macrophages are part of innate immunity. Choice B is incorrect because innate immunity is nonspecific and immediate, while adaptive immunity is specific and takes time to develop. Choice D is incorrect because physical barriers are a characteristic of innate immunity, not adaptive immunity.

Correct Answer: C

Rationale: The correct answer is C: Identifying and eliminating abnormal cells. This function is most relevant to cancer because the immune system's ability to recognize and destroy abnormal cells is crucial in preventing the development and spread of cancer. The immune system constantly surveys the body for cells that have mutated or become cancerous, and when identified, it initiates an immune response to eliminate them. This process is essential for maintaining the body's health and preventing cancerous cells from proliferating. Choice A (Suppressing cytokine release) is incorrect because cytokines play a role in regulating the immune response, which can be important in cancer immunity. Choice B (Promoting adaptive immunity only) is incorrect as both innate and adaptive immune responses are involved in combating cancer. Choice D (Limiting the effectiveness of phagocytes) is incorrect as phagocytes are important in recognizing and destroying cancer cells.