fig1

Figure 1. T cell activation. CD8⁺ T cells inspect the surface of cells they encounter and are activated if a T cell receptor binds to a presented pMHC-I complex, leading to downstream processes including proliferation, differentiation, and cytokine secretion. CD4⁺ T cells are similarly activated when binding pMHC-II complexes presented by professional APCs such as dendritic cells. A co-stimulating signal from CD28/CD80 (86) binding is required for full activation; its absence leads to T cell anergy. APC: antigen-presenting cell; MHC: major histocompatibility complex; TCR: T cell receptor