Binding of retinoblastoma and normal sera to retinoblastoma-derived cultured cells.

We have observed increased binding of retinoblastoma patients' sera to a retinoblastoma-derived cultured cell line (Y-79). This reactivity was mediated by the serum IgG fraction and was directed toward different tumor or target cell (Y-79, Molt, Raji, and fibroblasts) cultured in media containing fetal calf serum. Normal pooled serum IgG fractions did not demonstrate any similar binding. When target cells were cultured in media containing human serum instead of fetal calf serum, a considerable reduction in retinoblastoma sera binding activity was observed. Reactivity against target retinoblastoma cells could be reduced but not entirely eliminated by quantitative absorption with nonretinoblastoma (Molt) cells grown in media with fetal calf serum. Retinoblastoma and normal sera binding to autologous fibroblasts, nonautologous fibroblasts, and cultured melanoma cells was also minimal. These findings suggest that residual binding activity in the sera tested may be directed against retinoblastoma tumor antigens. The fetal calf serum component responsible for reactivity with certain retinoblastoma sera was shown by immunoprecipitation, competitive inhibition, and gel electrophoresis to be bovine serum albumin.