Seminal plasma-induced suppression of the respiratory burst of polymorphonuclear leukocytes and monocytes

Based on recent findings indicating suppression of lymphocytic functions by seminal plasma (SP) we tested the effects of SP from men with normo- and oligozoospermia (n = 7, each) on the generation of luminol-enhanced chemiluminescence (CL) of polymorphonuclear leukocytes (PMN) and monocytes (M psi) stimulated in vitro with zymosan. We found a complete suppression of CL of PMN and M psi by undiluted SP's, 1,000-fold dilutions still induced greater than or equal to 20 percent inhibition. There was no difference between normo- and oligozoospermic men in inhibition of CL both with PMN and M psi. Protein concentrations of SP's were closely the same; all SP were free of the complement components C4 and C3c. After dialysis of SP the inhibition of PMN - and M psi - generated CL was no longer present. Our results demonstrate that SP exerts extremely potent inhibition of cells mediating nonspecific defense and/or antigen presentation. The inhibitor appears to be of low molecular weight. These findings may be important for infections acquired by the genital tract and may provide an explanation for the immunotolerance of spermatozoa in the female reproductive system.