T cells are primarily involved in which type of immunity?

T cells are primarily involved in cell-mediated immunity, a key component of the adaptive immune response. This type of immunity is characterized by the activation of T cells which recognize and respond to specific antigens presented by infected or abnormal cells.

T cells play a critical role in identifying and eliminating cells that have been infected by pathogens, particularly viruses, as well as in combating cancerous cells. They do this through direct cytotoxic activity mediated by cytotoxic T lymphocytes (CD8+ T cells) or by helping other immune cells through helper T cells (CD4+ T cells). The ability of T cells to recognize specific antigens and mount a tailored response is a hallmark feature of adaptive immunity, distinguishing it from other types of immunity, such as humoral immunity, where B cells produce antibodies.

The other types of immunity mentioned do not primarily involve T cells. Humoral immunity, for instance, mainly relies on B cells and the antibodies they produce. Innate immunity encompasses first-line defenses like physical barriers and non-specific immune responses that are not reliant on T cells. Passive immunity, on the other hand, typically involves the transfer of antibodies from one individual to another and does not involve the activity of T cells.