Questions: Which of the following cell types initiates a secondary immune response? A) cytotoxic T cells D) plasma cells B) memory cells C) Schwann cells

The answer is B) memory cells.

Explanation for each option:

A) Cytotoxic T cells: These cells are involved in the direct killing of infected or cancerous cells. They play a crucial role in the primary immune response but are not responsible for initiating a secondary immune response.

B) Memory cells: These cells are responsible for initiating a secondary immune response. They are long-lived cells that were generated during the primary immune response and can quickly respond to a previously encountered antigen, providing a faster and more robust immune response upon re-exposure.

C) Schwann cells: These are not involved in the immune response. Schwann cells are a type of glial cell in the peripheral nervous system that helps in the formation of myelin sheaths around nerve fibers.

D) Plasma cells: These are differentiated B cells that produce antibodies during the primary immune response. They do not initiate a secondary immune response.

In summary, memory cells are the ones that initiate a secondary immune response by recognizing and responding more rapidly to antigens that the body has encountered before.