Which of the following statements concerned with multiple sclerosis (MS) is correct?

Correct Answer: A

Rationale: Rationale: Option A is correct because genetic factors have been identified as playing a role in predisposition to develop MS. Studies have shown a higher risk among individuals with family history. Option B is incorrect because environmental factors, such as vitamin D levels and viral infections, are known to influence MS development. Option C is incorrect as MS is more prevalent in North America and Europe. Option D is incorrect because MS is primarily mediated by T-cell responses, not autoantibodies.

Correct Answer: B

Rationale: The correct answer is B: Response that activates macrophages. Macrophages play a crucial role in controlling Leishmania infection by phagocytizing the parasites. Activating macrophages enhances their ability to kill the intracellular parasites, leading to effective immunity. Antibodies (choice A) are not as effective against intracellular pathogens like Leishmania. Mast cells (choice C) are primarily involved in allergic reactions, not protective immunity against parasites. Anti-bacterial response (choice D) is not directly relevant to combating Leishmania, an intracellular parasite.

Correct Answer: C

Rationale: The correct answer is C: Phagocytosis of microbes. Epithelial cells primarily act as a physical barrier to prevent the entry of microbes. Phagocytosis is a function of immune cells, not epithelial cells. A: Secretion of mucins helps trap pathogens. B: Secretion of antimicrobial peptides aids in defense. D: Tight junctions form a physical barrier between cells. Therefore, phagocytosis is not a direct mechanism exerted by epithelial cells at mucosal sites.

Correct Answer: D

Rationale: The correct answer is D because the binding of allergen-specific IgE to mast cells is actually a key event in anaphylactic shock, leading to the release of inflammatory mediators. Constriction of airways (A), loss of blood pressure (B), and hives (C) are all consequences of anaphylactic shock due to the systemic release of histamine and other mediators. IgE binding to mast cells triggers the release of these mediators, causing the symptoms associated with anaphylaxis. Therefore, D is the correct answer as it is not a consequence but rather an initiating event in anaphylactic shock.

Correct Answer: D

Rationale: Rationale for Correct Answer (D - Interferon): 1. Lymphokines are protein substances produced by lymphocytes. 2. Interferon is a type of lymphokine produced by lymphocytes during viral infections. 3. It helps in regulating the immune response and inhibiting viral replication. 4. Interferon moves from cell to cell carrying messages through the immune system. Summary of Incorrect Choices: A: Vaccine - Not a lymphokine, but a substance used to stimulate the immune system. B: Antigen - Not a lymphokine, but a substance that triggers an immune response. C: Antibody - Not a lymphokine, but a protein produced by the immune system to neutralize pathogens.