The c-kit+ Maturation Pathway in Mouse Thymic T Cell Development: Lineages and Selection

AbstractPositive selection of T cells begins with TCRαβlo thymic progenitors. Here, we show that the most efficient TCRlo progenitors are c-kit+ with intermediate levels of CD4 and CD8 (DPint). Positive selection of DPint TCRlo c-kit+ cells results in TCRmed 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 DPint c-kit+ progenitors fail positive selection, and become DPhi c-kit− cells that lose Bcl-2 expression. Some DPhi c-kit− blast cells can be salvaged to produce mature single-positive (SP) cells. DPint c-kit+ maturation to SP cells can occur in