Recognition of E‐cadherin on epithelial cells by the mucosal T cell integrin αM290β7 (αEβ7)

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Abstract
The integrin αM290β7 on the surface of a T cell hybridoma, MTC‐1, mediated adhesion of these cells to the mouse epithelial cell line CMT93. This interaction was critically dependent on the presence of divalent cations; Mn2+ strongly promoted adhesion, Ca2+ was ineffective and Mg2+ gave intermediate results. Antibodies to molecules on the surface of CMT93 cells were tested for inhibition of adhesion. One monoclonal antibody (mAb) against E‐cadherin, ECCD‐2, was found to have significant inhibitory activity. Other mAb to E‐cadherin and antibodies to other molecules had no effect. To show that inhibition by ECCD‐2 was specific for adhesion mediated by αM290β7, MTC‐1 cells were induced to adhere to CMT93 via the LFA‐1/ICAM‐1 pathway. For this purpose, the epithelial cells were treated with interferon‐γ and tumor necrosis factor‐α to induce ICAM‐1 expression and, in addition, αM290β7 on MTC‐1 cells was down‐regulated by culturing the cells in the absence of transforming growth factor β. Under these circumstances adhesion of MTC‐1 cells to CMT93 was inhibited by an antibody to LFA‐1 but not by ECCD‐2. Transfection of mouse L cells with cDNA for mouse E‐cadherin enabled MTC‐1 cells to adhere to them through the αM290β7 integrin; this interaction was inhibited both by ECCD‐2 and by blocking antibody against the integrin. These data strongly suggest that E‐cadherin is a principal ligand for αM290β7.