Which type of immunity do B cells and antibodies mediate?

Humoral immunity is specifically mediated by B cells and the antibodies they produce. This type of immunity involves the production of antibodies in response to antigens, which are foreign substances that enter the body. When B cells encounter an antigen, they can differentiate into plasma cells, which are responsible for the secretion of antibodies. These antibodies circulate in body fluids (or humors) and bind to the antigens, marking them for destruction and neutralizing their effects.

This process is distinct from cell-mediated immunity, which is primarily conducted by T cells and involves direct cellular responses to infected or malignant cells. Innate immunity refers to the body's first line of defense against pathogens, involving physical barriers, immune cells, and nonspecific responses. Passive immunity involves the transfer of antibodies from one individual to another, providing temporary protection but not involving the host's immune system in the antibody production process.

Thus, the association of B cells and antibody production with humoral immunity illustrates their critical role in the adaptive immune response, targeting specific pathogens and contributing to long-term immunity through memory cell formation.