Specificity and function of monoclonal antibodies directed against Ewing sarcoma cells.

A selection of 16 monoclonal antibodies has been produced against a fresh Ewing's sarcoma (ES) tumor mixed with a permanent ES cell line. The majority of antibodies identify an 80-kDa molecule, which is not detected on healthy tissues except on certain cultured monocytes. One antibody recognizes the CD2 ligand MIC2 and 2 antibodies (numbers 13 and 16) define a higher-molecular-mass antigen. Antibody 16 is also expressed on mesenchymal fibroblasts of bone marrow or fetal origin. Tumor-specific antigen expression is potentially linked to the chromosome 22 abnormality described in Ewing's sarcoma, products altered expression in tumors with the chromosome 11/22 translocation has not been shown. The putative chimeric protein on chromosome 11 is apparently not expressed to a great extent, as tested by Northern blotting; however, the fusion protein initiated on chromosome 22 and ending on chromosome 11 is readily seen on Northern blots. The altered expression of a number of cellular genes in addition to a novel gene product(s) originating from translocation events were expected to be identified by monoclonal antibodies selected by their unique binding pattern to Ewing's sarcoma (ES) cells.