Which types of hypersensitivity are mediated by antibodies?

Correct Answer: B

Rationale: The correct answer is B: Type I, II, III, and V. - Type I hypersensitivity involves IgE antibodies and immediate allergic reactions. - Type II hypersensitivity involves IgG and IgM antibodies attacking self-antigens on cells. - Type III hypersensitivity involves immune complex deposition. - Type V hypersensitivity involves autoantibodies stimulating receptors. Choices A, C, and D are incorrect because they do not include all types of hypersensitivity mediated by antibodies as specified in the question.

Correct Answer: A

Rationale: The correct answer is A. Cross-linking of IgE molecules on the mast cell surface triggers the release of mediators during Type I hypersensitivity. When allergens bind to IgE antibodies on mast cells, it leads to cross-linking of IgE molecules, causing the mast cell to release histamine and other inflammatory mediators. This process initiates the allergic response. Explanation for incorrect choices: B: Activation of complement proteins does not directly trigger mast cell degranulation in Type I hypersensitivity. C: Binding of IgG to antigen is characteristic of Type II and Type III hypersensitivity reactions, not Type I. D: Phagocytosis of allergens does not directly stimulate mast cells to release mediators in Type I hypersensitivity.

Correct Answer: C

Rationale: The correct answer is C (24-72 hours) for Type IV hypersensitivity reactions to develop. This type of reaction involves T cell-mediated immune responses, which take time to develop. Initially, sensitization occurs, followed by activation of memory T cells upon re-exposure to the antigen. This process typically takes 24-72 hours to manifest clinically. Choices A (Within minutes), B (1-3 hours), and D (5-7 days) are incorrect because Type IV reactions do not exhibit immediate responses like Type I hypersensitivity reactions (Choice A), nor do they typically take as long as 5-7 days to develop (Choice D). The time frame of 1-3 hours (Choice B) is too short for the characteristic delayed hypersensitivity reaction seen in Type IV responses.

Correct Answer: B

Rationale: The correct answer is B because correctly identifying the client prior to a blood transfusion helps prevent a type II hypersensitivity reaction, which occurs when the body attacks its own cells due to mismatched blood types. This action ensures that the client receives compatible blood, reducing the risk of a transfusion reaction. Administering steroids for a positive TB test (A) is unrelated to preventing a type II hypersensitivity reaction. Keeping the client free of the offending agent (C) is more relevant to preventing a type IV hypersensitivity reaction. Providing a latex-free environment for the client (D) is important for preventing a type I hypersensitivity reaction in latex-sensitive individuals, not type II reactions related to blood transfusions.

Correct Answer: C

Rationale: The correct answer is C: Afferent lymphatics. Dendritic cells migrate from tissues to lymph nodes through afferent lymphatics, which are small vessels that carry lymph into the lymph nodes. Once inside the lymph nodes, dendritic cells interact with T cells to initiate immune responses. The thoracic duct (A) drains lymph from the entire body into the bloodstream, not directly into lymph nodes. High endothelial venules (HEV) (B) are specialized blood vessels in lymph nodes where lymphocytes enter from the bloodstream, not dendritic cells. Efferent lymphatics (D) carry lymph out of the lymph nodes, not into them.