Abstract
Protective significance of some seminal plasma components is described. Lactoferrin is characterized as a primary defense factor against microbial invasion. The agglutinating factor in seminal vesicle fluid may prevent premature elimination of the spermatozoa by leukocytes infiltrating into the female genital tract. The protease inhibitors neutralize the activity of the proteases, thereby protecting the tissues and spermatozoa against proteolytic degradation. Antigens absorbed to spermatozoa during the ejaculation may protect the spermatozoa against the immune system of female reproductive tract. Ejaculated spermatozoa contain immunosuppressive substances that inhibit cell-mediated cytotoxicity as well as lymphocyte response to allogenic cells. These substances may constitute the system that prevents immune damage of spermatozoa.