Biochemical characterization of a rat spermatozoal peptide antigen and the induction of a reversible immunosuppression of fertility

: A rat spermatozoal polypeptide with 40 amino acid residues and a N-terminal lysine was purified to homogeneity by high performance liquid chromatography. Following incorporation of the peptide into pure phosphatidylcholine liposomes and immunization of female Wistar rats, a significant reduction of fertility occurred (chi 2 = 6.4, P less than .01). Following 4 months of recovery after the immunization fertility rates returned to normal. No adverse side effects on vital organs from the immunization were detected by light microscopy. The results may be indicative of a pathway for immunologic regulation of fertility.