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

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Abstract
A novel monoclonal antibody, 2E7, was shown by immunoprecipitation to be reactive with the αIELβ7 integrin and was employed to analyze the expression of this integrin in lymphocyte subsets and during T cell ontogeny. In adult lymph nodes, αIEL 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 αIEL 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 αIEL integrin, suggesting that the αIEL 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 αIELβ7 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.