Post-thymic T-cell development in the rat.

The presence or absence of CD4, CD8, Thy-1, RT6 and CD45RC revealed a number of T-cell subpopulations in the rat. Vascular thymus transplantation was used in RT7 congenics to establish the lineage relationship between these subpopulations by following phenotypic changes after thymus emigration. We found that recent thymic emigrants exhibit the Thy-1+/RT6-/CD45RC- phenotype and express either CD4 or CD8. Within 11 days after emigration, these cells differentiated into Thy-1-/RT6+/CD45RC+ cells. From 33 to 76 days following transplantation, a proportion of the latter lost RT6 and/or CD45RC expression, suggesting further differentiation. The pathway of 'mature' T-cell differentiation could be reconstructed from these data and analysis of the differences between T-cell subsets in thymectomized and normal control rats. End-stages of post-thymic T-cell differentiation in the rat were most likely to be Thy-1-/RT6+/CD45RC- and Thy-1-/RT6-/CD45RC+ T cells.