Two human tumor-associated antigens, p155 and p210, detected by monoclonal antibodies.

BALB/c mice were immunized with human melanoma cells and their spleen cells hybridized with NS-1 myeloma cells. The hybrids were screened for the production of antibodies that bound to melanoma cells. Two hybridomas of interesting specificity were identified and cloned. Hybridoma 5.1 produce an IgG1 antibody that binds to about half of the melanomas and carcinomas tested. The target is a polypeptide with an apparent molecular weight of 210 kilodaltons on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The antigen, denoted p210, is also expressed in normal adult brain and in certain fetal tissues. Hybridoma 6.1 produces an IgM antibody that binds to about 50% of the melanomas, and 80% of the kidney carcinomas tested. The antigen defined by this antibody in melanomas has an apparent molecular weight of 155 kilodaltons and is denoted p155. It has not been observed on any normal adult or fetal tissues. The antigen present in the kidney carcinomas was not p155, but rather consisted of two proteins of approximately 60,000 and 250,000-300,000 daltons. This observation suggests the possibility that the antigenic determinant recognized by antibody 6.1 may be present on several distinct protein molecules.