A new monoclonal antibody (POG-1) detects a differentiation antigen of porcine granulosa and thecal cells and indicates heterogeneity of thecal-stromal cells.

To identify the differentiation antigen of ovarian cells, we raised a murine monoclonal antibody (POG-1 antibody) reactive to porcine granulosa and thecal cells in the ovary. Immunofluorescence staining showed that expression of the POG-1 antigen on granulosa and theca interna cells increased gradually in accordance with follicular development. The thecal cells just outside the basal lamina surrounding the follicles did not express the antigen, whereas some stromal cells around the theca externa layer in the large follicles did express it. These expression profiles indicated the heterogeneity of thecal-stromal cells and that the POG-1 antigen was a differentiation-related antigen of granulosa and thecal cells. Luteal cells also expressed the antigen. In organs other than the ovary, some endocrine and exocrine cells, such as Leydig cells and secretory cells of the breast, expressed the antigen. The POG-1 antigen was purified from granulosa cells by immunoaffinity chromatography. Polyacrylamide gel electrophoresis profiles showed that the antigen consisted of two specific proteins; the major one had a molecular mass of 77, and the other had a molecular mass of 81 kilodaltons. Analysis of the purified POG-1 antigen may contribute to understanding the differentiation mechanism of granulosa and thecal cells.