Functional maturation of two murine medullary-type CD8SP thymocytes

TCRαβCD4-CD8+ thymocytes are heterogeneity. They may undergo phenotypic and functional maturation within thymic medulla. Medullary-type CD8SP thymocytes were divided into seven subsets based on phenotypic analysis, and their precursor-progeny relationship along with the differential pathway was also delineated. To further testify the validity of the maturation pathway, we purified 6C10-CD69+ cells representing the early stage and 6C10-Qa-2+ cells representing the later stage among medullary-type CD8SP thymocytes and compared their functional maturation levels. CD8+ T cells of spleen were used as the control. It is shown that there is no obvious difference of proliferation ability among these three subsets; however, intracytoplasmic cytokine assay shows that there is a hier archy of IFN-γ and TNFα secretion among these subsets, strikingly comparable to their phenotypic status among medullary type CD8SP thymocytes. The bioassays of IL-2 and IFN-γ in culture supernatant give the similar results.