25.23 : T 细胞类型和功能

Activated T cells with CD4 markers give rise to the effector helper and regulatory T cells, while the effector cytotoxic T cells arise from T cells with CD8 markers.

CD4 T cells differentiate into helper T cell subsets — T_H1, T_H2, and T_H17.

T_H1 effector cells primarily assist the activation and differentiation of CD8 cells into cytotoxic T cells.

Additionally, the T_H1 cells release cytokines for macrophage activation, essential for cell-mediated immunity.

In contrast, the differentiated T_H2 effector subset secretes cytokines like IL-4 that act as co-stimulatory molecules for B cell activation.

T_H17 cells produce IL-17, which triggers inflammatory reactions against extracellular microbes. Unregulated IL-17 production has been implicated in autoimmune diseases.

Similarly, T regulatory cells can suppress self-reactive lymphocytes outside the lymphoid organs.

The cytotoxic T cells patrol the body to neutralize host cells that are cancerous or infected by intracellular pathogens like viruses and foreign cells introduced during transplants.