DEVELOPMENTAL EXPRESSION OF THE ALPHA(IEL)BETA(7) INTEGRIN ON T-CELL RECEPTOR-GAMMA-DELTA AND T-CELL RECEPTOR-ALPHA-BETA T-CELLS

A novel monoclonal antibody, 2E7, was shown by immunoprecipitation to be reactive with the alpha(IEL)beta(7) integrin and was employed to an alyze the expression of this integrin in lymphocyte subsets and during T cell ontogeny. In adult lymph nodes, alpha(IEL) was expressed at lo w levels by 40-70% of CD8(+) T cells and < 5% of CD4(+) T cells. Howev er, virtually all intestinal intraepithelial lymphocytes and similar t o 20% of lamina propria CD4(+) T cells were 2E7(+), indicating a prefe rential expression of this integrin on mucosal T cells. Examination of alpha(IEL) integrin expression during thymus ontogeny revealed that s imilar to 3-5% of fetal or adult thymocytes were 2E7(+). Interestingly , early in fetal thymus ontogeny, similar to 40% of 2E7(+) cells expre ssed T cell receptor (TcR)-gamma delta and this subset persisted throu gh birth. A developmental switch occurred such that 2E7(+) TcR(-) CD4( -)8(+) cells detected on fetal day 19 were followed by 2E7(+) TcR-alph a beta CD4(-)8(+) cells in the neonatal thymus. The latter population persisted throughout thymus ontogeny into adulthood. Interestingly, a subset of TcR-gamma delta V gamma 3(+) day 16 fetal thymocyte dendriti c epidermal cell (DEC) precursors were 2E7(+), but all mature DEC expr essed high levels of alpha(IEL) integrin, suggesting that the alpha(IE L) integrin was acquired late in DEC maturation. This possibility was strengthened by immunohistochemical localization of the majority of 2E 7(+) gamma delta and alpha beta T cells to the medullary regions of th e thymus. Overall, the results demonstrate a developmentally ordered e xpression pattern of the alpha(IEL)beta(7) integrin that suggests a co mmon function for this integrin during TcR-gamma delta and -alpha beta CD4(-)8(+) T cell thymocyte development or perhaps in effector functi ons for these subsets.