What is the primary role of Helper T cells in the immune response?

Correct Answer: C

Rationale: Helper T cells primarily secrete cytokines to activate other immune cells. This is crucial for coordinating and amplifying the immune response. They do not kill infected host cells (A), as that is the role of cytotoxic T cells. Producing antibodies (B) is the function of B cells. Suppressing immune responses (D) is the role of regulatory T cells, not Helper T cells.

Correct Answer: C

Rationale: The correct answer is C, displaying antigen fragments for T cell recognition. MHC molecules bind to antigen fragments and present them on the cell surface for T cells to recognize. This process is crucial for activating the immune response. Choice A is incorrect as MHC molecules do not secrete cytokines. Choice B is incorrect as MHC molecules do not directly destroy pathogens. Choice D is incorrect as MHC molecules do not produce antibodies; that is the function of B cells.

Correct Answer: B

Rationale: The correct answer is B: Plasma cells. Plasma cells are a type of white blood cell that produces antibodies in response to antigens. They are essential in the immune response to help fight off infections and other diseases. Helper T cells (A) assist other immune cells but do not directly produce antibodies. Cytotoxic T cells (C) are responsible for killing infected cells, not producing antibodies. Regulatory T cells (D) help regulate the immune response but do not produce antibodies. In summary, only plasma cells are specifically designed to produce antibodies in the immune system.

Correct Answer: B

Rationale: The correct answer is B (IgG and IgM) because in Type II hypersensitivity, antibodies target antigens on cell surfaces or tissues. IgG and IgM antibodies are involved in this type of immune response by binding to antigens and triggering cell destruction through complement activation or phagocytosis. IgE and IgA (choice A) are typically associated with Type I and Type III hypersensitivity, respectively. IgD (choice C) is primarily involved in B cell activation, while IgA (choice D) is more commonly associated with mucosal immunity.

Correct Answer: A

Rationale: The correct answer is A: Crohn's disease. Granulomas are a characteristic feature of Crohn's disease, forming in response to chronic inflammation in the gastrointestinal tract. Granulomas consist of immune cells and are seen in the affected tissues of Crohn's patients. Choice B: Grave's disease is an autoimmune condition affecting the thyroid gland, not typically associated with granulomas. Choice C: Anaphylaxis is a severe allergic reaction involving the immune system's response, but it does not lead to granuloma formation. Choice D: Eczema is a skin condition characterized by inflammation and itching, but it does not typically involve granulomas.