Figure 1.

Production and differentiation of T cells. Naive CD4⁺ and CD8⁺ T (T_N), naive regulatory T (Tregs) cells, and double-negative (DN) T cells are released from the thymus. Then CD4⁺ and CD8⁺ T cells get activated and differentiate into effector (T_E) cells after encountering antigens. Only a small part of T_E develops into memory T cells, including stem-like memory (T_SCM), central memory (T_CM), transitional memory (T_TM), effector memory (T_EM), and terminal effector (T_TE) cells. In HIV immunological non-responders, the number of T_N cells produced by the thymus is reduced, while the proportion of activated T cells is increased. DP, double-positive; TCRαβ, T cell receptor alpha and beta; TCRγδ, T cell receptor gamma and delta; Foxp3, factor forkhead box P3.