EXPRESSION OF MUC1 MUCIN ON ACTIVATED HUMAN T-CELLS - IMPLICATIONS FOR A ROLE OF MUC1 IN NORMAL IMMUNE REGULATION

MUC1 mucin is expressed by normal and malignant epithelial cells and i s thought to function through cell-cell interactions and transmembrane signal transduction events, Secreted cancer-associated MUC1 is immuno suppressive and inhibits human T-cell proliferation, We report here th at newly synthesized MUC1 is expressed on the surface of mitogen-activ ated human T cells and is also found in soluble form in the supernatan ts from cultures of mitogen-activated human T cells, After removal of the mitogenic stimulus from the T-cell cultures, MUC1 expression is do wnregulated. The addition of anti-MUC1 monoclonal antibody to mitogen- activated cultures partially inhibits the T-cell proliferative respons e. These data suggest that MUC1 serves an immunodulatory function for human T lymphocytes.