Which cell type bridges innate and adaptive immunity?

Correct Answer: B

Rationale: The correct answer is B: Dendritic cells. Dendritic cells bridge innate and adaptive immunity by capturing antigens, processing them, and presenting them to T cells to initiate adaptive immune responses. NK cells (A) are part of innate immunity, while plasma cells (C) produce antibodies in adaptive immunity. Mast cells (D) are involved in allergic responses, not bridging innate and adaptive immunity.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Hypersensitivity in immunology refers to an exaggerated or inappropriate immune response. 2. This excessive response can lead to tissue damage and various immune-mediated conditions. 3. Choice A accurately describes this concept. Summary: - Choice A is correct as it accurately defines hypersensitivity. - Choice B is incorrect as hypersensitivity involves an exaggerated immune response, not an inability to mount one. - Choice C is incorrect as hypersensitivity is not a low-level immune reaction. - Choice D is incorrect as hypersensitivity is not a mechanism for faster immune response, but rather an overreaction.

Correct Answer: B

Rationale: The correct answer is B, Grave's disease, for Type V hypersensitivity. In Type V hypersensitivity, antibodies target cell surface receptors, leading to abnormal stimulation or blockage. In Grave's disease, antibodies target the thyroid-stimulating hormone receptor, leading to excessive thyroid hormone production. Multiple sclerosis (A) is an example of Type IV hypersensitivity involving T cell-mediated response. Rheumatoid arthritis (C) is an example of Type III hypersensitivity involving immune complex deposition. Type 1 diabetes mellitus (D) is an example of Type II hypersensitivity involving antibody-mediated destruction of cells.

Correct Answer: D

Rationale: The correct answer is D: T cell apoptosis. Anaphylaxis is a severe allergic reaction that involves a rapid immune response. T cell apoptosis is not a typical symptom of anaphylaxis. Rationale: 1. A: Sudden drop in blood pressure is associated with anaphylaxis due to systemic vasodilation. 2. B: Massive edema is common in anaphylaxis due to increased vascular permeability. 3. C: Severe bronchoconstriction is a hallmark of anaphylaxis, leading to respiratory distress. 4. D: T cell apoptosis is not a characteristic feature of anaphylaxis. T cells play a role in adaptive immunity, not the immediate hypersensitivity reaction seen in anaphylaxis. Summary: T cell apoptosis is not typically associated with anaphylaxis, unlike the other symptoms listed which are common manifestations of this severe allergic reaction.

Correct Answer: B

Rationale: The primary effector cell in delayed-type hypersensitivity is T cells. T cells play a crucial role in initiating and orchestrating the immune response in delayed hypersensitivity reactions. Upon exposure to the antigen, T cells are activated and release cytokines that recruit and activate macrophages, leading to the inflammatory response characteristic of delayed-type hypersensitivity. Mast cells are involved in immediate hypersensitivity reactions mediated by IgE. Neutrophils are primarily involved in acute inflammation and combating bacterial infections. B cells are responsible for antibody production in humoral immunity, not in delayed hypersensitivity reactions. Therefore, the correct answer is B: T cells.