IMMUNOSTAINING OF HUMAN MELANOMAS BY A MONOCLONAL-ANTIBODY TO B700 MOUSE MELANOMA ANTIGEN

Previous studies have shown that B700, an albumin-like murine melanoma antigen, has a human homologue termed H700. Polyclonal antibodies to B700 also bind to all cultured human, swine and hamster melanoma cells , suggesting that B700 is a ''pan-melanoma'' antigen. The objects of t his investigation were: (a) to determine if 2-3-3, a monoclonal antibo dy to B700, can be used to identify human melanomas in formalin-fixed, paraffin-embedded tissues, and (b) to determine the specificity and p otential diagnostic value of 2-3-3. Forty-eight of the 49 human melano mas, including spindle melanoma cells, stained positively, as did five of the eight pigmented naevi including cellular spindle naevi. Twenty -six of the 32 human non-melanomatous lesions were negative for 2-3-3 staining (weakly positive on one breast carcinoma and positive on five neural tumours). These results indicate that 2-3-3, a monoclonal anti body to the mouse melanoma antigen B700, can be used to identify H700 in archival specimens. 2-3-3 may have an advantage over HMB45, which i s the most commonly used antibody for melanoma diagnosis, because of i ts immunoreactivity with spindle melanocytic lesions. Antibodies to B7 00 may prove to be a useful adjunct in the diagnosis of human melanoma and related lesions.