A novel heteromorphic human cell surface alloantigen, gp60, defined by a human monoclonal antibody.

A human mAb (DSM1) generated from a patient immunized with irradiated allogeneic melanoma cells detects a new cell surface alloantigen of restricted cell type distribution. The Ag is a 60,000-Da glycoprotein (gp60) that displays considerable heteromorphism in its cytosolic and cytoskeletal (52 to 62 kDa) and membrane forms (60 to 64 kDa). The gp60 Ag has been purified using lectin affinity, ion exchange, and Mono P fast performance liquid chromatography. Rabbit antiserum against purified gp60 recognizes a homologous gp60 molecule on DSM1-nonreactive cells. Molecular properties of gp60 and a partial amino acid sequence of a tryptic gp60-derived peptide distinguish it from other known human alloantigens. This is the first report of a human alloantigenic system whose definition required a cell type other than those of bone marrow derivation.