Placental protein 14 (PP14) content and immunosuppressive activity of human cervical mucus.

Extracts of cervical mucus contain measurable levels of placental protein 14 (PP14), a protein known to suppress proliferative responses of human peripheral blood lymphocytes. Such extracts have been shown to exert suppressive activities on allogeneically stimulated peripheral blood lymphocytes in a dose-dependent manner. However, there was no correlation between the PP14 content of cervical mucus samples and their suppressive activities. Such activity could not be removed from the extracts by dialysis, suggesting high molecular weight mediators. These results indicate that there may be an immunosuppressive factor in human cervical mucus which functions to protect inseminated sperm in a potentially immunologically hostile environment in the female reproductive tract.