What is the primary role of memory cells in the immune system?

Explanation: During antibody-mediated immunity, B cells produce antibodies, also known as immunoglobulins. Antibodies are Y-shaped proteins that specifically recognize and bind to antigens on the surface of pathogens or foreign substances. This binding marks the pathogens for destruction by other immune cells or neutralizes their harmful effects.

Incorrect choices:

a. Cytokines are small proteins that serve as signaling molecules in the immune system, regulating the behavior and activity of immune cells. B cells can secrete cytokines, but their primary function is antibody production.

b. Cytotoxic granules contain substances like perforin and granzymes and are released by cytotoxic T cells to induce apoptosis in infected or abnormal cells. B cells do not produce cytotoxic granules.

d. Perforin is a protein released by cytotoxic T cells and natural killer cells to create pores in the membrane of infected cells, leading to cell death. B cells do not produce perforin.

Explanation: Cytotoxic T cells (CD8+ T cells) are the effector cells of cell-mediated immunity. Their primary role is to directly recognize and kill infected or abnormal cells, such as virus-infected cells or cancer cells. Cytotoxic T cells release cytotoxic granules containing perforin and granzymes, which induce apoptosis (cell death) in the target cells.

Incorrect choices:

a. Helper T cells, not cytotoxic T cells, recognize antigens presented by macrophages and play a crucial role in activating other immune cells.

b. B cells are responsible for producing antibodies against pathogens during the humoral immune response, not cytotoxic T cells.

d. Regulatory T cells (suppressor T cells) are involved in regulating the immune response to prevent excessive inflammation and tissue damage, not cytotoxic T cells.