Decreased suppression of antibody-dependent cellular cytotoxicity by seminal plasma in unexplained infertility

Objectives: To determine whether seminal plasma (SP) from unexplained infertile males has different suppressive activity on antibody-dependent cellular cytotoxicity (ADCC) than SP from fertile males or SP from males of couples with known infertility factor. Design: Comparative clinical/experimental study. Setting: In vitro fertilization program in a university hospital and a hospital research laboratory. Patient(s): A total of 245 SP samples from 174 infertile and 16 fertile couples were compared. Intervention(s): SP suppression of ADCC was measured by using human (51)chromium-labeled red blood cells (RBC), sensitized with IgG-rabbit anti-human-RBC as targets and peripheral blood lymphocytes as effector cells. Main Outcome Measure(s): Suppressive activity of each sample was determined by calculating Cr-51-release in the presence and absence of SP. Result(s): When analyzed with respect to sperm number, motility, and morphology, suppressive activities of samples with normal semen analyses (n = 142) were significantly higher (x = 37% +/- 14%) than suppressive activities of abnormal samples (n = 103; x = 32% +/- 13%). There was no strong correlation of suppressive activity to other semen parameters. Within the andrologically normal males. SP from the unexplained infertile couples (n = 15) showed significantly lower suppressive activity (x = 24% +/- 11%) compared with the SP from fertile males (n = 16; x = 35% +/- 13%) and from couples with female infertility factor (n = 65; x = 39% +/- 14%). Conclusion(s): Loss of suppressive activity is associated with unexplained infertility, even in male patients who previously were considered normal by traditional methods of semen analysis. (C) 2001 by American Society for Reproductive Medicine.