Immunodiffusion and immunoelectrophoretic analyses, including absorption tests, were used to determine the heterogeneity of antigens in bull spermatozoa and reproductive fluids and to characterize antisera against these antigens. Antisera were produced against bull seminal plasma, seminal vesicle fluid, cauda epididymal plasma, blood serum, washed ejaculated spermatozoa, washed cauda epididymal spermatozoa and sperm fractions. Four sperm-specific antigens were detected. One antigen was located in the sperm head, one in the sperm tail and two others were common to both the head and tail. The tailspecific antigen was detected only after mechanical rupture of washed spermatozoa. The major antigens of spermatozoa are localized in the cell membrane and acrosome. Apparently, sperm antigens were present in cauda epididymal plasma and seminal plasma. These antigens may have been released by physiologically normal spermatozoa or they may represent end products of sperm dissolution within the epididymis and vas deferens. Their presence makes immunological analyses of reproductive fluids difficult.
Cauda epididymal plasma and seminal vesicle fluid shared at least two antigens not present in blood serum. These antigens in cauda epididymal plasma coated the sperm cell and probably were secreted by the caput epididymidis. Coating antigens were more tightly bound to ejaculated spermatozoa than to spermatozoa from the cauda epididymidis.