ANTIGENIC DETERMINANTS OF HUMAN SPERM TAIL FIBROUS SHEATH PROTEINS

Mouse anti-fibrous sheath antisera (MAFA) produced by immunizing mice with purified preparations of human sperm tail fibrous sheath (FS) rea cted with the principal piece of less than 10% of freshly isolated spe rmatozoa which were immotile and probably dead. Following their dememb ranation by detergents or repeated freezing and thawing, all spermatoz oa were stained. This was also demonstrated on spermatozoa dried onto slides, but the undiluted xenoantisera showed additional reactivity wi th the acrosomal zone (AZ). Using immunogold electron microscopy, the target antigens were ultrastructurally localized to the FS, and a few spermatozoa showed some reaction at the AZ subacrosomal perinuclear th eca. Following titration of the antibodies, the anti-AZ-reaction becam e undetectable at a dilution of 1:20 while their reactivity with the p rincipal piece continued to a 1:400-dilution. These results indicated that the xenoantisera probably contained an additional unrelated antib ody component which reacted with the AZ. Western blotting and staining of purified FS with MAFA detected seven major protein bands with MW r anging between 25 kDa and 97.4 kDa. In human testes, the 1:50 diluted MAFA reacted with sperm tails only, indicating the late expression of the antigenic determinants during spermatogenesis. MAFA did not react with oesophagus, stomach, duodenum, ileum, nasal lining tissues, uteru s, pericardium, pancreas, thyroid gland, or cultured fibroblasts. The xenoantisera did, however stain the skin epidermis and cultured kerati nocytes which exhibited filamentous cytoplasmic staining although thei r target antigens could not be biochemically identified. These results indicate that the FS proteins express antigenic determinants which ar e not shared with other cytoskeletal elements within the sperm flagell um or a variety of somatic tissues.