[Demonstration of a 100-110 kd immunosuppressive fraction in the seminal fluid of swine].

The boar seminal fluid was fractionated in order to purify semen immunosuppressive factors. This species was chosen for its extremely abundant semen which allows large scale purifications and analyses. The fractions were tested on Balb/c mice spleen cells stimulated with LPS or PHA. The most active fraction was found in the 100-110 kd molecular weight range. The immunosuppressive activity occurred on both B and T cells, but was higher on the former. The active molecule is likely to be a protein. Another fraction of greater than 500 kd MW was also immunosuppressive but its activity disappeared by concentration. It possibly contained aggregates of the 100 kd molecules. The biological role of these immunosuppressive agents could be to protect sperm against female local immune reactions. Similar molecules in human semen might exist and favor the occurrence of acquired immunodeficiency syndrome in male homosexuals.