If the BCR of a developing cell has no binding affinity for self-antigens in the bone marrow the B cell will be:

Correct Answer: D

Rationale: The correct answer is D: Allowed to mature and enter the periphery. In this scenario, since the developing B cell has no binding affinity for self-antigens in the bone marrow, it will not undergo clonal deletion or anergy. Therefore, it will be allowed to mature and enter the periphery where it can encounter foreign antigens and participate in the immune response. Choices A and B are incorrect because clonal deletion and anergy are mechanisms used to eliminate or inactivate self-reactive B cells to prevent autoimmunity. Choice C is incorrect because a B cell without self-binding affinity is not a cause of autoimmunity in the periphery.

Correct Answer: C

Rationale: The correct answer is C because smallpox was indeed introduced to the Americas by European explorers, leading to devastating effects on the Native populations who had no immunity. This weakened the Natives' ability to fight back against the Europeans. Option A is incorrect as there was no ongoing smallpox epidemic in the Americas before the arrival of the Europeans. Option B is also incorrect as there is no evidence that the Native populations used a lethal form of vaccination against smallpox. Option D is incorrect as only option C accurately explains the impact of smallpox on the Native populations in relation to European conquest.

Correct Answer: B

Rationale: The correct answer is B because Helicobacter pylori is not typically associated with nosocomial infections. Nosocomial infections are usually caused by bacteria commonly found in healthcare settings, such as Clostridium difficile, which is mentioned in choice D. Choices A, C, and D are correct as nosocomial infections can be caused by both Gram-negative and Gram-positive bacteria, often antibiotic-resistant species, and commensal flora bacteria like Clostridium difficile.

Correct Answer: C

Rationale: The correct answer is C: CARD. CARD stands for Caspase Activation and Recruitment Domain, which is crucial for the assembly of the inflammasome complex. It facilitates the recruitment and activation of caspase enzymes, leading to inflammatory responses. Leucine rich repeats (A) and TIR domain (B) are not directly involved in the assembly of the inflammasome. Therefore, the correct choice is C, as it specifically pertains to the structural domain essential for this process.

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.