Figure 2.

In the T cell activation cascade, the T cell receptor (TCR), along with co-stimulatory and co-receptor molecules like CD28, IL2R, and IL7R, orchestrates activation via the PI3K-Akt-cMyc axis. In contrast, programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) serve as inhibitory checkpoints, dampening T cell activation by modulating the PI3K-Akt pathway. The diagrammatic representation employs red arrows to denote the pathways promoting T cell activation, while blue arrows indicate the pathways conferring inhibitory signals that antagonize activation.