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

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: Memory in the immune system refers to the ability of immune cells, particularly memory B cells and memory T cells, to recognize and respond more quickly and effectively to specific antigens upon subsequent exposure. This leads to a faster and stronger secondary immune response.

Incorrect choices:
b. The ability of immune cells to differentiate between self and non-self antigens refers to the concept of immune tolerance, which helps prevent the immune system from attacking the body's own cells and tissues.
c. The process of phagocytosis by macrophages is a mechanism by which immune cells engulf and destroy pathogens and cellular debris, but it is not directly related to memory in the immune system.
d. The ability of B cells to produce antibodies is an essential part of the primary immune response, but it is not specific to memory in the immune system.