What happens when immune complexes are not cleared in Type III hypersensitivity?

Correct Answer: B

Rationale: The correct answer is B because when immune complexes are not cleared in Type III hypersensitivity, they deposit in tissues, activating complement cascades and causing inflammation. This leads to tissue damage and the recruitment of inflammatory cells. A: Immune complexes do not directly activate T cells in Type III hypersensitivity. C: Phagocytosis of immune complexes can lead to cell activation and inflammation. D: Immune complexes do not suppress antibody production in Type III 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.

Correct Answer: B

Rationale: The correct answer is B: Signal propagation in T cells. CD3 is a protein complex found on the surface of T cells that is crucial for T cell receptor signaling and activation. It helps propagate signals within T cells, leading to T cell activation and immune responses. Choice A (Antigen binding) is incorrect as CD3 is not directly involved in antigen binding. Choice C (Signal propagation in B cells) is incorrect as CD3 is specific to T cells, not B cells. Choice D (T cell homing to lymph nodes) is incorrect as CD3 is not responsible for the physical migration of T cells to lymph nodes.