THE GAMMA-DELTA T-LYMPHOCYTES OF THE PERINATAL MURINE THYMUS

We have previously shown that the adult thymus contains three subsets of gamma delta T cells that can be defined by the expression of Thy-1 and heat-stable antigen (HSA). In this study, the number of cells in e ach of these thymic gamma delta populations was investigated at differ ent stages throughout life. In adult mice, the populations stayed rela tively constant, however, in contrast, there were major variations in them early in development. It was shown that only two of the gamma del ta populations were present in the prenatal thymus, a major population of Thy-1(+) HSA cells, and a smaller population of Thy-1(+) HSA(+) ce lls. However, after birth, most of the Thy-1(+) HSA cells appear to lo ose the Thy-1 antigen, forming the third population of HSA(-) Thy-1(-) cells. The adult configuration of populations appeared to be establis hed within the first week after birth. Therefore, whereas the gamma de lta populations stayed relatively constant from this time point onward s, there were major Variations early in development. Throughout life, most gamma delta thymocytes are CD4(-) CD8(-), however, in the neonata l thymus, there are some CD4(+) and CD8(+) gamma delta thymocytes, and these are contained in the Thy-1(+) HSA(-) population.