Expression of sialyl Lewis(x) antigen on human T cells

Sialyl Lewis(x) (sLe(x)) antigen, which has been introduced as tumor-associated cell surface carbohydrates, was demonstrated to be expressed on a subpopulation of human CD4+ and CD8+ T cells. It was also demonstrated that the majority of gamma delta T cells as well as natural killer cells expressed a high level of sLe(x) antigen. The sLe(x) expression on T cells were up-regulated by activation with various T cell stimulants. The sLe(x)+ CD4+ T cells were enriched in CD4+CD45RO+ memory type of T cells but not in CD4+CD45RA+ T cells. Moreover, sLe(x)+ CD4+ T cells were demonstrated to show higher proliferative responses to T cell stimulants such as CD4+CD45RO+ T cells. These results initially clarified the expression of sLe(x) carbohydrate on human T cells and indicated the important role of sLe(x)-expressing T cells in immune responses.