Dendritic cells induce MUC1 expression and polarization on human T cells by an IL-7-dependent mechanism. 
The MUC1 transmembrane mucin is expressed on the surface of activated human T cells; however, the physiologic signals responsible for the regulation of MUC1 in T cells are not known.  The present studies demonstrate that IL-7, but not IL-2 or IL-4, markedly induces MUC1 expression on CD3+ T cells.  MUC1 was also up-regulated by IL-15, but to a lesser extent than that found with IL-7.  The results show that IL-7 up-regulates MUC1 on CD4+, CD8+, CD25+, CD69+, naive CD45RA+, and memory CD45RO+ T cells.  In concert with induction of MUC1 expression by IL-7, activated dendritic cells (DC) that produce IL-7 up-regulate MUC1 on allogeneic CD3+ T cells.  DC also induce MUC1 expression on autologous CD3+ T cells in the presence of recall Ag.  Moreover, DC-induced MUC1 expression on T cells is blocked by a neutralizing anti-IL-7 Ab.  The results also demonstrate that DC induce polarization of MUC1 on T cells at sites opposing the DC-T cell synapse.  These findings indicate that DC-mediated activation of Ag-specific T cells is associated with induction and polarization of MUC1 expression by an IL-7-dependent mechanism.