Expression of the Tn antigen on T-lymphoid cell line Jurkat

Expression of the Tn antigen on a T-lymphoid cell line, Jurkat, was investigated using an anti-Tn monoclonal antibody, MLS 128. Immunoprecipitation or immunoaffinity chromatography of a lysate of Jurkat cells led to the isolation of a 120 kDa glycoprotein carrying the Tn antigen. This glycoprotein and leukosialin (CD43) were indistinguishable on SDS-PAGE and as to immunoreactivity with MLS 128. Leukosialin from an erythroid cell line, K562, exhibited no reactivity with MLS 128 despite that this leukosialin has several GalNAc alpha-Ser(Thr) structures. Pulse-chase experiments with the Jurkat leukosialin showed that newly synthesized leukosialin acquired the antigenecity after a lag of about 30 min, whereas incorporation of GalNAc into the leukosialin occurred earlier. These results indicate that the Tn antigen is expressed on leukosialin and that its epitopic structure is more complex than GalNAc alpha-Ser(Thr).