The role of lymphokine-activated cell-associated antigen. II. Distribution and correlation with cell cycle.

It has previously been shown that killer-blocking monoclonal antibody (KBA MAb) recognizes lymphokine-activated cell-associated antigen (LAA) involved in broad-reactive killer. (BRK) cell-mediated cytotoxicity. We now report that LAA is expressed on all lymphoid cells, though the amount of LAA on unstimulated lymphocytes is low. In contrast, lymphocytes activated in vitro with either concanavalin A, alloantigens, lipopolysaccharide, or recombinant interleukin 2 express high levels of LAA. In addition, in vivo activated lymphocytes, such as OK-432-activated lymphocytes and tumor-infiltrating lymphocytes express higher levels of LAA than unstimulated lymphocytes. We also demonstrate that the expression of LAA is restricted in T-cell lymphomas and a M phi cell line, while myelomas, fibrosarcomas, and carcinomas do not express LAA. Cell cycle analysis using propidium iodide and KBA MAb showed that LAA expression was closely correlated with the transition of cells from G1a to G1b phase.