Antibody activities of serum and uterine fluid samples from rabbits isoimmunized against sperm fractions

Sperm and uterine fluid samples were collected from rabbits that had been isoimmunized systemically and were challenged locally against a sperm extract (soluble fraction of lithium diiodosalicylate extraction) and a sperm-pellet extract (soluble fraction of Nonidet NP.40 treatment of pellet remaining after LIS extraction). Antibody activity against the sperm plasma membrane was found in serum and uterine fluid samples from the sperm-extract immune rabbits, as indicated by an inhibition of sperm attachment to ova in vitro and by indirect immunofluorescent staining on unfixed sperm. A strong acrosome staining was noted with fixed sperm. These samples did not show fluorescent staining of swollen heads of sperm or react with blastocysts. The immune samples from rabbits injected with sperm-pellet extract displayed the opposite reactions. These samples did not react with the plasma membrane of sperm but the IgA antibodies of the uterine fluids caused immunofluorescent staining of the swollen heads of sperm and the blastocyst cell membranes. Uterine fluid from this group of rabbits also inhibited blastocyst development in vitro. Immune samples from rabbits immunized against untreated epididymal sperm gave all the positive reactions.