Effect of intra-rectal administration of boar seminal immunosuppressive fraction on mouse lymphocytes.

The repeated deposition of an immunosuppressive fraction isolated from boar vesicular gland secretion into the rectum of healthy male and female mice reduced responses of lymphocytes to mitogens in vitro. Rectal deposition of the immunosuppressive component also led to a decrease in the activity of plaque-forming cells. These findings indicate that repeated rectal deposition of semen may compromise some aspects of the immune system and may be an important cofactor in the development of viral or bacterial infections among homosexual men.