TN ANTIGEN IS EXPRESSED ON LEUKOSIALIN FROM T-LYMPHOID CELLS

Various T-lymphoid cells were labeled with [H-3] glucosamine and then cell lysates were prepared from them. The Tn antigen was immunoprecipi tated and analyzed by sodium dodecyl sulfate-polyacrylamide gel electr ophoresis followed by fluorography. The Tn antigen was found to be exp ressed on leukosialin, a major glycoprotein of T-lymphoid cells. The c arbohydrate moieties of leukosialin were isolated from Jurkat and Molt 4 cells by alkaline borohydride treatment. The leukosialin in both ca ses predominantly contained single N-acetylgalactosamine residues, con sistent with expression of the Tn antigen. Tryptic glycopeptides conta ining antigenic sites were isolated using an MLS 128 immunoaffinity co lumn and purified by gel filtration and reverse phase column chromatog raphies. Sequence analyses revealed that all the glycopeptides obtaine d contained three consecutive residues of N-acetylgalactosamine-Ser/Th r, supporting the idea that the epitopic structure is a cluster of N-a cetylgalactosamine-Ser/Thr.