Immunomodulation by human seminal plasma: a benefit for spermatozoon and pathogen?

The immunosuppressive effect of human seminal plasma and its implications for sperm survival are reviewed. Human semen contains high concentrations of prostaglandins that can effect a cytokine-mediated switch away from a cell-mediated immune response. This effect on antigen presenting cells would induce a state of non-responsiveness to sperm antigens in the female reproductive tract. It is postulated that the induction of anergy to sperm antigen may be fundamental to the continuing fecundity of the individual. However, although this immune system modulation will benefit the spermatozoa, the response to infective agents present in semen will also be affected, which may play a critical role in the aetiology and progress of sexually transmitted disease.