Immunohistochemical localization of interferon-gamma in normal human ovary

There is increasing evidence that cytokines are important intraovarian non-steroidal regulators. The aim of the present study was to evaluate the presence in the human ovary of interferon (IFN)-gamma, a cytokine produced by T lymphocytes after mitogenic or antigenic stimulation. Very low levels of IFN-gamma (0.025-0.057 IU/ml) were found in follicular fluid of large spontaneously maturing follicles, in the ovarian vein (< 0.01-0.079 IU/ml) or peripheral blood (< 0.01-0.06 IU/ml). The avidin-biotin immunocytochemical technique, with appropriate monoclonal antibodies, was used to localize IFN-gamma-positive cells, human leukocyte antigen (HLA)-DR molecules, activated T cells, T helper/inducer cells and T cytotoxic/suppressor cells. IFN-gamma-positive cells were only detected in preovulatory follicles, associated with the follicular basal lamina, thecal vessels and interstitial tissue. In the same large follicles very few T helper/inducer cells were detected, but a high proportion of T lymphocytes expressed the CD8 phenotype in the theca, interstitial tissue and follicular cavity. No IFN-gamma-positive cells were observed in preantral and small antral follicles. The results indicate that the human ovary contains immunoreactive IFN-gamma, suggesting that the cytokine plays a paracrine role in human ovarian function.