With regard to NADPH oxidase, which of the following statements in not correct?

Correct Answer: C

Rationale: The correct answer is C because NADPH oxidase is not constitutively expressed as a complex of 5 subunits in unstimulated cells. Instead, it is assembled and activated upon stimulation, such as during the respiratory burst following phagocytosis. Choice A is correct as NADPH oxidase is indeed involved in the respiratory burst. Choice B is correct as mutations in NADPH oxidase subunits lead to impaired pathogen killing and recurrent infections. Choice D is correct as NADPH oxidase controls the production of reactive oxygen species.

Correct Answer: B

Rationale: Correct Answer: B - Hematopoietic stem cells are not typically found within secondary lymphoid tissues because they are located in the bone marrow where they give rise to various blood cells. In contrast, secondary lymphoid tissues like lymph nodes and spleen primarily consist of mature immune cells and support immune responses. Naïve lymphocytes (A), dendritic cells (C), and antigens (D) are commonly found in secondary lymphoid tissues as they play crucial roles in the immune response.

Correct Answer: B

Rationale: Step 1: Memory response produces antibodies of higher affinity due to affinity maturation. Step 2: Memory response involves class switching, leading to production of IgG, IgA, and IgE. Step 3: IgM is predominant in primary response, but memory response shifts towards other classes. Summary: Choice B is correct as memory response produces antibodies of higher affinity and different classes. Choices A and C are incorrect as memory response does not typically result in more IgM or lower affinity antibodies. Choice D is incorrect as only choice B is accurate.

Correct Answer: B

Rationale: Step 1: SCID is a genetic disorder affecting the immune system. Step 2: Inherited genetic mutations cause abnormalities in immune cells. Step 3: These mutations lead to severe deficiencies in immune function. Step 4: Choice B accurately reflects the genetic basis of SCID. Summary: Choice A is incorrect because SCID is not caused by HIV. Choice C is incorrect as it oversimplifies the immune deficiencies in SCID. Choice D is incorrect because SCID primarily affects immune cells, not stem cells.

Correct Answer: C

Rationale: Rationale: C is incorrect because naïve lymphocytes actually enter the lymph node through the afferent lymphatic vessel, not the efferent. A carries lymphocytes into the lymph node, and D is true since antigens enter through afferent vessels. B is correct, as naïve T cells are found in the paracortex.