Detection of HL-A and Other Cell-Surface Antigens on Cultured Cells by a Cytotoxic Plating Inhibition Test

Summary A cytotoxic plating inhibition test detected HL-A and other cell-surface antigens on cultured tumor and normal cells. Cultured target cells were typed for HL-A specificities to avoid misinterpretation of HL-A reactions for tumor-associated activity. The validity of the antigens detected was supported by comparisons with lymphocyte typing. When sera from cancer patients were analyzed for HL-A reactivity by being screened against lymphocyte samples from 80 different donors, between 5 and 10% possessed this activity. Aside from these HL-A reactions, a significant degree of cytotoxicity not associated with specific histologic types of tumors was found with sera from cancer patients on cells cultured from tumors and even from normal tissue. Moreover, antigens were detected with sera from normal individuals as well as patients. The demonstration of antigens on cell membranes of cultured cells other than tumor-associated HL-A antigens has implications for interpretations of tests on cultured tumor cells.