Figure 4.

Possible developmental trajectory of exhausted T cells and the comparison and relationship with memory or effector T cells. Under continuous antigen stimulation, T cells transform from precursor exhausted cells into terminally exhausted T cell populations, which mainly depends on the expression of the transcription factor TCF-1, accompanied by the high expression of a variety of inhibitory receptors. The relationship between the differentiation of T cell subsets and exhausted T cells remains to be explored. PD-1, PD ligand 1; TCF1, T cell factor-1; TIM-3, T-cell immunoglobulin domain and mucin domain protein 3; LAG-3, lymphocyte activation gene 3; TOX, thymocyte selection-associated high-motility group (HMG) box protein.