The chemotactic properties of porcine seminal components toward neutrophils in vitro

Our objectives were to investigate the mechanisms of postbreeding inflammat ion in swine by examining the chemotactic properties of polymorphonuclear n eutrophilic granulocytes (PMN) and of various populations of spermatozoa an d seminal plasma. Epididymal. spermatozoa from two boars obtained under ste rile conditions, washed ejaculated spermatozoa from two boars, and pooled s eminal plasma from eight boars of known fertility were examined for chemota xis to PMN. The chemotaxis of blood-derived PMN in response to sperm and se minal plasma was evaluated and expressed as a percentage of a positive cont rol (lipopolysaccharide-activated blood plasma). The mean chemotactic effec t of washed sperm alone (4.4 +/- 0.04) and of epididymal sperm alone (3.4 /- 0.06) was not different from that of the negative controls (3.1 +/- 0.05 ) of McCoy's medium with 10% heat-inactivated fetal calf serum. A marked ch emotactic effect was detected when washed ejaculated and epididymal sperm w ere incubated with blood plasma, compared with blood plasma without spermat ozoa (P < 0.001). Washed sperm in blood plasma (86.2 <plus/minus> 5.6) and epididymal sperm in blood plasma (83.9 +/- 7.7) were different from blood p lasma alone (11.2 +/- 1.5), but no differences were detected between the tw o populations of sperm. This effect, however, was not completely inhibited by heat inactivation of the blood plasma. The chemotactic response of washe d ejaculated and epididymal spermatozoa incubated in lipopolysaccharide-tre ated, heat-inactivated blood plasma were greater than that of the negative control (P < 0.05). Polymorphonuclear neutrophilic granulocyte migration to ward seminal plasma was similar to the negative control (4.0 <plus/minus> 0 .04 vs 3.1 +/- 0.05). It seems that porcine epididymal sperm and ejaculated sperm activate chemotactic components in porcine blood plasma and heat-ina ctivated blood plasma, suggesting that, at least partially, a heat-stable ( noncomplement) blood plasma component may be involved in sperm-induced PMN chemotaxis. In contrast, porcine seminal plasma was not chemotactic to PMN. These results support the hypothesis that spermatozoa play an active role in initiating postbreeding endometritis.