Developmental expression of the αIELβ7 integrin on T cell receptor γδ and T cell receptor αβ T cells

Abstract A novel monoclonal antibody, 2E7, was shown by immunoprecipitation to be reactive with the α IEL β7 integrin and was employed to analyze the expression of this integrin in lymphocyte subsets and during T cell ontogeny. In adult lymph nodes, α IEL was expressed at low levels by 40–70% of CD8 + T cells and < 5% of CD4 + T cells. However, virtually all intestinal intraepithelial lymphocytes and ˜20% of lamina propria CD4 + T cells were 2E7 + , indicating a preferential expression of this integrin on mucosal T cells. Examination of α IEL integrin expression during thymus ontogeny revealed that ˜3–5% of fetal or adult thymocytes were 2E7 + . Interestingly, early in fetal thymus ontogeny, ˜40% of 2E7 + cells expressed T cell receptor (TcR)‐γδ and this subset persisted through birth. A developmental switch occurred such that 2E7 + TcR − CD4 − 8 + cells detected on fetal day 19 were followed by 2E7 + TcR‐αβ CD4 − 8 + cells in the neonatal thymus. The latter population persisted throughout thymus ontogeny into adulthood. Interestingly, a subset of TcR‐γδ Vγ3 + day 16 fetal thymocyte dendritic epidermal cell (DEC) precursors were 2E7 + , but all mature DEC expressed high levels of α IEL integrin, suggesting that the α IEL integrin was acquired late in DEC maturation. This possibility was strenghthened by immunohistochemical localization of the majority of 2E7 + γδ and αβ T cells to the medullary regions of the thymus. Overall, the results demonstrate a developmentally ordered expression pattern of the α IEL β 7 integrin that suggests a common function for this integrin during TcR‐γδ and ‐αβ CD4 − 8 + T cell thymocyte development or perhaps in effector functions for these subsets.