Which of the following vaccines is recommended for healthcare workers to protect against hepatitis B?

Explanation: B cells are a type of lymphocyte that plays a crucial role in the immune response by recognizing and binding to specific antigens. When a B cell encounters an antigen that matches its specific receptor, it becomes activated and differentiates into plasma cells, which produce antibodies against the antigen.

Incorrect choices:

b. Cytotoxic T cells are responsible for directly attacking and killing infected or abnormal cells during cell-mediated immunity. They do not primarily recognize antigens during the immune response.

c. Macrophages are antigen-presenting cells that engulf and process pathogens to present their antigens to other immune cells, such as T cells and B cells. While they are involved in antigen recognition, they are not the primary cells responsible for this function.

d. Red blood cells do not have a direct role in antigen recognition or the immune response. Their primary function is to transport oxygen throughout the body.

Explanation: Memory cells recognize and respond rapidly to previously encountered pathogens. Memory cells are a type of immune cell that are formed after an initial infection or vaccination. They "remember" the specific pathogen and allow the immune system to mount a faster and stronger response upon subsequent exposures to the same pathogen, providing long-term immunity.

Incorrect choices:

a. Memory cells do not directly attack pathogens in the body. They serve as a form of immune "memory" to help the body respond more effectively to future infections.

b. Memory cells do not produce antibodies upon initial pathogen exposure. B cells are responsible for producing antibodies in response to the pathogen.

d. Memory cells do not regulate the body's temperature during an infection. Temperature regulation is mainly controlled by the hypothalamus in the brain in response to infection or other stimuli.