Which cells play a central role in Type I hypersensitivity reactions?

Correct Answer: B

Rationale: The correct answer is B: Mast cells. Mast cells play a central role in Type I hypersensitivity reactions by releasing histamine, cytokines, and other inflammatory mediators in response to allergens. This triggers the allergic response. Neutrophils (A), Macrophages (C), and Dendritic cells (D) are not central to Type I hypersensitivity reactions. Neutrophils are involved in acute inflammation, macrophages play a role in phagocytosis and antigen presentation, and dendritic cells are important in initiating adaptive immune responses.

Correct Answer: B

Rationale: The correct answer is B: Antibody binding to cell surface antigens, triggering complement activation or phagocytosis. In Type II hypersensitivity, antibodies bind to antigens on host cells, leading to complement activation or phagocytosis by immune cells. This results in cell damage or destruction. Immune complex deposition (A) is more characteristic of Type III hypersensitivity. Mast cell degranulation (C) is seen in Type I hypersensitivity. T cell-mediated cytotoxicity (D) is associated with Type IV hypersensitivity, not Type II. Therefore, choice B is the most accurate mechanism of tissue damage in Type II hypersensitivity.

Correct Answer: B

Rationale: Granuloma formation is characterized by the persistent recruitment of macrophages around undigested antigens. Initially, macrophages attempt to phagocytose the antigen but fail to digest it completely, leading to the formation of a granuloma. This process is a protective mechanism to isolate the antigen and prevent its spread. IgE-mediated mast cell activation (choice A) is associated with allergic reactions, not granuloma formation. Deposition of immune complexes in tissues (choice C) is linked to immune complex-mediated diseases, not granuloma formation. Complement-mediated cell lysis (choice D) involves the destruction of target cells by the complement system, which is not directly related to granuloma formation.

Correct Answer: A

Rationale: The correct answer is A. If the client states they don't need to go to the hospital after using the epinephrine autoinjector, additional instruction is needed. The rationale is that after using an epinephrine autoinjector, it is crucial to seek medical attention immediately due to the potential for severe allergic reactions. Choice B is incorrect because carrying two autoinjectors is recommended in case the first dose is not effective. Choice C is incorrect as it demonstrates good practice in tracking the expiration date. Choice D is incorrect as it is acceptable to inject through clothes in an emergency situation.

Correct Answer: C

Rationale: Rationale: VDJ gene rearrangement occurs during lymphocyte development to generate diverse antigen receptors. This process occurs in the bone marrow, specifically in the early stages of B cell development. In the bone marrow, B cell precursors undergo VDJ recombination to create unique antibody specificity. Germinal centers are sites for B cell activation and proliferation, not gene rearrangement. Lymph nodes and spleen are secondary lymphoid organs where mature lymphocytes are activated, not where VDJ recombination occurs.