What type of receptor is found on B cells for antigen recognition?

Correct Answer: B

Rationale: The correct answer is B because B cells express B cell receptors (BCR) on their surface for recognizing antigens. BCRs consist of immunoglobulin molecules that bind specifically to antigens. T cell receptors (A) are found on T cells, not B cells. Fc receptors (C) bind to the Fc region of antibodies, while complement receptors (D) recognize complement proteins, not antigens. Therefore, the BCR is the specific receptor on B cells for antigen recognition.

Correct Answer: B

Rationale: The correct answer is B: Fc fragment. The Fc fragment of an antibody determines its physiological effects by interacting with immune cells and other effector molecules. It mediates processes like opsonization, complement activation, and antibody-dependent cell-mediated cytotoxicity. The Fab fragment (A) contains the antigen-binding site but does not directly influence physiological effects. The variable region (C) is part of both the Fab and Fc portions and contributes to antigen specificity but does not solely determine physiological effects. The antigen-binding site (D) is located within the Fab portion and is responsible for binding to specific antigens, not for exerting physiological effects.

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.