In which one of the following situations would a graft-versus-host reaction be MOST likely to occur?

Correct Answer: C

Rationale: The correct answer is C because the recipient is X-irradiated, which impairs their immune system, making them more susceptible to graft-versus-host reaction when receiving cells from a different strain. In this scenario, the adult strain A spleen cells injected into an X-irradiated strain AB adult, the immune system of the recipient is compromised, increasing the likelihood of the reaction. Choice A is less likely as newborns have an immature immune system. Choice B is less likely because x-irradiation of the donor reduces the likelihood of a reaction. Choice D is less likely because the recipient is a newborn, having an immature immune system.

Correct Answer: A

Rationale: Rationale for Correct Answer (A): A: The statement is incorrect. Tolerance is antigen-specific, meaning the immune system can distinguish between self and non-self antigens. Paralysis of immune cells leads to a lack of response against specific antigens, not many. Therefore, this statement is incorrect. Summary of Incorrect Choices: B: Tolerance is actually more easily induced in B cells than in T cells due to their inherent self-tolerance mechanisms. C: Tolerance is actually more easily induced in neonates due to their developing immune system, but it can be induced in adults as well. D: Tolerance can be induced by both simple and complex molecules, but the level of ease may vary depending on the specific context.

Correct Answer: B

Rationale: The correct answer is B: stimulating antibody production. Vaccinations introduce a weakened or inactive form of a pathogen to trigger the immune response. This leads to the production of specific antibodies that recognize and attack the pathogen upon future exposure. Antibodies play a crucial role in neutralizing and eliminating pathogens. A: Inhibiting antigen production is incorrect because vaccines aim to stimulate the immune system's response to antigens, not inhibit their production. C: Inhibiting white blood cell production is incorrect because white blood cells are vital components of the immune system and are not suppressed by vaccinations. D: Stimulating red blood cell production is incorrect because vaccinations do not have a direct impact on red blood cell production, which is primarily regulated by the body's own mechanisms.

Correct Answer: B

Rationale: The correct answer is B because Hepatitis A is transmitted through the fecal-oral route by consuming contaminated food or water. Stopping the consumption of raw clams, which could potentially be contaminated, is an appropriate precaution. A is incorrect as it mentions Hepatitis B transmission through shared needles and unclean tattoo equipment, which is not relevant to Hepatitis A. C is incorrect as avoiding all physical contact is an extreme measure and unnecessary for preventing Hepatitis A transmission. D is incorrect as boiling drinking water for 10 minutes is not a specific preventive measure for Hepatitis A, which is mainly spread through contaminated food and water.

Correct Answer: B

Rationale: Rationale: B is correct because HIV can be transmitted through contact with infected blood, with the highest concentration of the virus found in blood. Other body fluids like sputum, saliva, cerebrospinal fluid, urine, and semen can also contain the virus. Incorrect Choices: A is incorrect as HIV is not necessarily transmitted when symptoms manifest or during the asymptomatic period. C is incorrect as HIV can be transmitted through various routes, not just sexual contact. D is incorrect as HIV is not transmitted through airborne means.