Positive selection of T cells begins with TCRαβ(lo) thymic progenitors. Here, we show that the most efficient TCR(lo) progenitors are c-kits with intermediate levels of CD4 and CD8 (DP(int). Positive selection of DP(int) TCR(lo) c-kit+ cells results in TCR(med) CD69+ c-kit+ transitional intermediates that show increased TCRVβ frequencies to selecting superantigen (SAg) that are committed to the CD4 or CD8 pathway. The cells on the c-kit+ maturation pathway maintain Bcl-2 expression. Most DP(int) c-kit+ progenitors fail positive selection, and become DP(hi) c-kit- cells that lose Bcl-2 expression. Some DP(hi) c-kit- blast cells can be salvaged to produce mature single-positive (SP) cells. DP(int) c-kit+ maturation to SP cells can occur in <12 hr in vitro on thymic stromal monolayers.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy
- Infectious Diseases