What is confirmed about antibody-mediated immunity (AMI)?

Antibody-mediated immunity (AMI), also known as humoral immunity, is primarily characterized by the production of antibodies by B lymphocytes (B cells). When B cells encounter specific antigens, they can differentiate into plasma cells that synthesize and secrete antibodies. These antibodies circulate in the blood and lymph, binding to pathogens such as bacteria and viruses, neutralizing them, and marking them for destruction by other components of the immune system. This mechanism is essential for defending against a wide range of pathogens and is not limited to one type of infection.

The other options present incorrect associations with AMI. AMI is not restricted solely to viral infections; it also plays a significant role in defending against bacterial infections and other pathogens. Phagocytic natural killer (NK) cells are primarily associated with the innate immune response and do not directly mediate antibody production or function. Additionally, the humoral immunity response is defined by the action of B lymphocytes, not T lymphocytes; T lymphocytes are involved in cell-mediated immunity, which targets infected or cancerous cells rather than secreting antibodies.