25.24 : 細胞傷害性T細胞を介した免疫応答

Cytotoxic T cells target body cells infected by viruses, intracellular bacteria, or parasites. They also eliminate cancerous cells and foreign cells introduced during transplants.

Their ability to monitor, identify, and eliminate cells presenting non-self antigens is termed immunological surveillance.

For successful activation, TCRs on naive CD8 T cells must meet their target antigens presented on MHC-I molecules expressed on all nucleated cells.

Additionally, dendritic cells engulf dying virus-infected cells or tumor cells and display these antigens complexed with MHC I for these T cells.

After binding the infected cell, the naive CD8 T cell receives cytokine co-stimulatory signals from a helper T cell, eventually differentiating into a cytotoxic T cell.

This effector T cell releases granules with perforin, creating pores in the membrane of infected cells for cytolysis.

Some granules release granzymes, which enter and rupture the cell via apoptosis.

In some cases like cancer, the cytotoxic cells may also release cytokines that activate apoptotic genes or lymphotoxins to destroy the target cell.