Effect of bovine seminal plasma on neutrophil phagocytosis of bull spermatozoa

Abstract

Seminal plasma was obtained from bulls of known fertility and was assessed for its effect on serum-induced phagocytosis of bull spermatozoa. A non-dialysable component was found to inhibit neutrophil phagocytic uptake of spermatozoa. The component was not destroyed by heating (56°C for 30 min) or removed by ether. Use of a bactericidal assay confirmed the inhibition and suggested that inhibition does not permanently impair neutrophil function. Immunoperoxidase staining demonstrated the presence of bovine IgM, IgG, and IgG2 on spermatozoa incubated in serum. Affinity of spermatozoa for the immunoglobulins was reduced when seminal plasma was added to the serum. These results suggest that bull seminal plasma can regulate phagocytic ingestion of spermatozoa. While the mechanism of this regulation remains obscure, it may be important in providing protection to spermatozoa immediately after ejaculation.