FIG. 1.
Mechanisms involved in thymic differentiation of TIM cells. T cell development in the thymus produces many lineages of mature T cells. (A) When the TCR of a single positive CD8 (SP8) cell recognizes an MHC-Ia molecule expressed on TEC, it results in the development of a conventional CD8+ T cell. (B) In the context of MHC-Ib expression, SP8 thymocytes can be successfully selected either by TECs or HCs. While SP8 cells selected on TECs have “a more naive” phenotype, the same precursors selected by HCs and exposed to interleukin-4 (IL-4) derived from PLZF-expressing thymocytes convert into TIM cells. (C) Reduced TCR signaling in SP8 cells in the presence of IL-4 induces Eomes expression and TIM phenotype acquisition. IL-4 has little effect on Eomes induction when T cells receive a strong TCR signal giving rise mainly to conventional naive SP8 cells. TEC, thymic epithelial cell; HC, hematopoietic cell.