Retinal S-antigen and retinoblastoma: a monoclonal antibody and flow cytometric study

Retinal S-antigen was demonstrated in the WERI-Rb1 and to a lesser extent the Y-79 tissue cultured retinoblastoma cell lines as well as an ethanol-fixed, paraffin-embedded retinoblastoma by an indirect immunoperoxidase technique using monoclonal antibody MAbA9-C6, and by flow cytometric analysis (FCM) using MAbA9-C6 and MAbA1-G5. In fixed tissue sections, S-antigen immunoreactivity was restricted and localized to small numbers of retinoblastoma cells, including Flexner-Wintersteiner rosettes. By FCM, MAbA9-C6 bound to 15.4% of WERI-Rb1 cells and to 10.99.7% of Y-79 cells whereas MAbA1-G5 bound to 14.66% of WERI-Rb1 and to 4.23% of Y-79 cells respectively. Cell cycle analysis showed that S-antigen was predominately expressed in the resting (G0/G1) phase. The usefulness of MAbA9-C6 in studying the embryological development of the retina and as a marker protein for studying antigenic expression and modulation in retinoblastomas is discussed.