Expression of an endothelial surface antigen on activated human lymphocytes: lymphocyte subset distribution and...

In this study we have utilized a monoclonal antibody, B721, to demonstrate the expression of an endothelial surface antigen on activated human lymphocytes. Using one- and two-color flow cytometry we have demonstrated that this antigen appears in vitro on cultured lymphocytes stimulated by mitogen or by MLC. The appearance and expression of the antigen are similar regardless of the stimulus. The antigen first appears on Day 2 of culture and expression continues through Day 6 of culture. At the time of its maximum expression, the antigen is present on a majority of B lymphoblasts and CD8 T lymphoblasts, but is present on only a subpopulation of CD4 T lymphoblasts. This antigen appears distinct from other lymphocyte activation antigens, endothelial antigens, and trophoblast antigens. It may play a role in lymphocyte activation and immune responses.