True or False: Immune disorders are always associated with an overactive immune system.

Correct answer: B

Explanation: T cells, specifically cytotoxic T cells (CD8+ T cells), are responsible for cell-mediated immunity. They directly recognize and attack infected or abnormal cells, leading to their destruction. This process is crucial in controlling viral infections and cancer cells.

Incorrect choices:
a. B cells, not T cells, are responsible for the production of antibodies during the humoral immune response.
c. Phagocytosis of pathogens is mainly carried out by macrophages and neutrophils, not T cells.
d. Allergic reactions are primarily mediated by a different type of T cells called helper T cells (CD4+ T cells), not cytotoxic T cells.

Explanation: The secondary immune response provides long-lasting immunity because of the presence of memory B cells and memory T cells. These memory cells "remember" the specific antigen and can quickly mount a strong and effective immune response upon re-exposure to the same antigen, providing long-term protection.

Incorrect choices:

a. The primary immune response is primarily mediated by IgM antibodies, while the secondary immune response involves the predominance of IgG antibodies, which are more effective and provide long-lasting immunity.

b. The secondary immune response occurs after the primary immune response and is faster, not slower, due to the presence of memory cells.

c. Memory cells are a key component of the secondary immune response, playing a central role in providing rapid and robust immunity.

VI. Immune Disorders and Clinical Considerations: