A differentiation-related molecule on the cell surface of human granulosa cells.

We raised a monoclonal antibody (OG-1) specifically reactive to human ovarian granulosa cells. Indirect immunofluorescence staining of freshly isolated granulosa cells from preovulatory follicles showed the OG-1 antigen on the cell surface of granulosa cells. The antigen was purified from granulosa cells by immunoaffinity chromatography. Under reducing or nonreducing conditions, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of the purified antigen showed two specific protein bands, corresponding to mol wt of 125 and 145 kilodaltons. Immunohistologically, the OG-1 antigen on granulosa cells of primary follicles seemed to increase during follicular development. After ovulation, the antigen was detected on granulosa cells during corpus luteum formation. The antigen expression began to decrease on corpus luteum days 10-12 and disappeared on corpus luteum days 13-14. Luteal cells of pregnancy did not express the OG-1 antigen. Granulosa cells in atretic follicles expressed the OG-1 antigen. On the contrary, thecal or small luteal cells did not express it throughout the menstrual cycle. These results indicate that OG-1 antigen is a differentiation-related surface antigen of human granulosa cells.