Idiotypic determinants are located within

Correct Answer: A

Rationale: The idiotypic determinants are unique antigenic determinants located within the hypervariable regions of heavy and light chains. These regions are highly variable and contribute to the diversity of antibodies. The correct answer is A because idiotypic determinants are specific to the variable regions of antibodies, not the constant regions. Choices B, C, and D are incorrect because idiotypic determinants are not found in the constant regions or hinge region of antibodies. The variability in the hypervariable regions allows antibodies to recognize and bind to a wide range of antigens, making them crucial for the specificity of the immune response.

Correct Answer: A

Rationale: The correct answer is A: IgG. IgG is the class of immunoglobulins that crosses the placenta from the mother to the fetus, leading to high concentrations in newborns. IgM is the first class produced in response to infection but is not present in high levels in newborns. IgA is primarily found in mucosal areas and secretions, not in high concentrations in the blood. IgD is mainly present on the surface of B cells and has limited presence in the bloodstream. Therefore, IgG is the most abundant immunoglobulin in the blood of a human newborn due to passive transfer from the mother.

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: The correct answer is A: a single terminal sugar residue. Blood group A and B antigens are determined by the presence of specific sugar molecules at the terminal end of glycoproteins on red blood cells. The specificity is based on the addition of a single sugar residue - either N-acetylgalactosamine (A antigen) or galactose (B antigen) to the H antigen precursor. This single terminal sugar residue determines the blood group specificity. Choice B is incorrect because amino acids are not involved in determining blood group antigens. Choice C is incorrect as blood group antigens are determined by single sugar residues, not multiple differences in the carbohydrate portion. Choice D is incorrect as blood group antigens are based on sugar residues, not protein differences.

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.