Which of the following vaccines is typically recommended for older adults to prevent complications from pneumonia?

Explanation: T cells are a type of lymphocyte that plays a central role in cell-mediated immunity. They can recognize and destroy abnormal cells, including cancer cells, through direct cell-to-cell interactions.

Incorrect choices:

b. B cells produce antibodies in response to specific pathogens, but they do not directly attack cancer cells.

c. Antibodies are protein molecules that can bind to specific antigens on pathogens, but they do not have a direct role in attacking cancer cells.

d. Macrophages are phagocytic cells that engulf and destroy foreign substances, including pathogens, but they are not the primary cells responsible for recognizing and attacking cancer cells.

Explanation: B cells are a type of lymphocyte that plays a central role in the adaptive immune response. When activated by the presence of specific antigens, B cells differentiate into plasma cells, which are responsible for producing large quantities of antibodies that can target and neutralize the invading pathogen.

Incorrect choices:

a. T cells are another type of lymphocyte that is involved in cell-mediated immunity, where they directly attack infected or abnormal cells. They do not produce antibodies.

b. Natural killer cells are part of the innate immune system and are responsible for killing infected or cancerous cells. They are not involved in antibody production.

d. Macrophages are phagocytic cells that engulf and destroy pathogens and debris in the body. While they play a crucial role in immune responses, they do not produce antibodies.