Functional maturation of two murine medullary-type CD8SP thymocytes

TCR alpha beta (+)CD4(-)CD8(+) thymocytes are heterogeneity. They may under go phenotypic and functional maturation within thymic medulla, Medullary-ty pe CD8SP thymocytes were divided into seven subsets based on phenotypic ana lysis, and their precursor progeny relationship along with the differential pathway was also delineated. To further testify the validity of the matura tion 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 obv ious difference of proliferation ability among these three subsets; however , intracytoplasmic cytokine assay shows that there is a hierarchy of IFN-ga mma and TNF alpha secretion among these subsets, strikingly comparable to t heir phenotypic status among medullary type CD8SP thymocytes. The bioassays of IL-2 and IFN-gamma in culture supernatant give the similar results.