Fc and C3b receptors on cultured retinoblastoma cells

Fc and C3b receptors were identified on cultured retinoblastoma cells. Labeled receptor protein bound to affinity gels prepared with IgG, Aggregated IgG, and Fc but not to control gels prepared from Fab'2 or Sepharose-4B alone. Eluted Fc receptors was partially characterized by polyacrylamide gel electrophoresis. Molecular weight of the isolated receptor or its subunit was approximately 4.3 X 10(4) daltons. Cultured retinoblastoma cells were found to rosette with human indicator erythrocytes specific for C3b and Fc receptors. This study indicates that considerable reactivity between retinoblastoma patients' sera and cultured tumor cells may be mediated by these receptors as well as by reactivity toward retinoblastoma antigens.