Immunology: AJ-FS9 monoclonal antibody detects masked antigens within the human sperm tail fibrous sheath

Abstract

AJ-FS9 is one of a new series of monoclonal antibodies (mAbs) raised by immunizing mice with isolated human sperm tail fibrous sheath (FS). Using indirect immunofluorescence (IIF) of human spermatozoa dried onto slides, the AJ-FS9 mAb reacted with the principal piece of occasional spermatozoa. Following their enzymatic treatment with trypsin, dispase or collagenase, but not sulphatase, all the spermatozoa were stained at their principal piece. The ultrastructural localization of the antigens to the FS was established by immunogold electron microscopy, which showed the distribution of gold particles on the FS outer surface of spermatozoa sequentially treated with 1% Triton and dispase; spermatozoa demembranated by Triton alone showed no reaction. For biochemical characterization, spermatozoa were lysed with 1% Triton, and the sperm pellet was run through a reducing sodium dodecyl sulphate-polyacrylamide gel electrophoresis, Western blotted and immunostained with AJ-FS9. The results showed the reaction of the antibody with three protein bands with molecular masses ranging between 46 and 56 kDa. IIF screening of human testicular cryostat sections with AJ-FS9 mAb showed its reactivity with occasional sperm tails; but following their dispase treatment, all spermatozoa were stained. The restricted staining of the assembled FS of maturing sperm tails indicated the late appearance of the antigens during spermatogenesis. The antibody did not react with sperm cell precursors or other cell types within/without the seminiferous tubules. Untreated and dispase-treated frozen sections of skin, oesophagus, tongue, liver, kidney, stomach, ileum or their blood vessels showed no reaction.(ABSTRACT TRUNCATED AT 250 WORDS)