Carcinoembryonic antigen, a tumor-associated glycoprotein induces defective lymphocyte function

Standard carcinoembryonic antigen(s) (CEA) obtained commercially, and CEA preparations from cell membranes and spent media of cultured human malignant melanotic melanoma (HMMC-ShAc and HMMC-ShAm) and of human colon adenocarcinomas (Levo c, Levo m, SW-403 c and SW-403 m) suppressed human peripheral blood lymphocyte (PBL). CEA preparations obtained from products of in vitro synthesis mediated by mRNA coding for CEA enhanced, whereas glycosylation-deficient preparations of CEA obtained from tumor cells harvested from growth media supplemented with nontoxic levels, i.e. 0.3 microgram/ml of tunicamycin, had no effect on immunoglobulin synthesis by human PBL. CEA caused defective lymphocyte: sheep red blood cell rosette production. It is suggested that CEA is an immunoregulatory glycoprotein synthesized by human tumor cells. The carbohydrate moiety of the glycoprotein is the regulatory determinant.