AJ-FS9 MONOCLONAL-ANTIBODY DETECTS MASKED ANTIGENS WITHIN THE HUMAN SPERM TAIL FIBROUS SHEATH

AJ-FS9 is one of a new series of monoclonal antibodies (mAbs) raised b y immunizing mice with isolated human sperm tail fibrous sheath (FS). Using indirect immunofluorescence (IIF) of human spermatozoa dried ont o slides, the AJ-FS9 mAb reacted with the principal piece of occasiona l spermatozoa. Following their enzymatic treatment with trypsin, dispa se or collagenase, but not sulphatase, all the spermatozoa were staine d at their principal piece. The ultrastructural localization of the an tigens to the FS was established by immunogold electron microscopy, wh ich showed the distribution of gold particles on the FS outer surface of spermatozoa sequentially treated with 1% Triton and dispase; sperma tozoa demembranated by Triton alone showed no reaction. For biochemica l characterization, spermatozoa were lysed with 1% Triton, and the spe rm pellet was run through a reducing sodium dodecyl sulphate-polyacryl amide gel electrophoresis, Western blotted and immunostained with AJ-F S9. The results showed the reaction of the antibody with three protein bands with molecular masses ranging between 46 and 56 kDa. IIF screen ing of human testicular cryostat sections with AJ-FS9 mAb showed its r eactivity with occasional sperm tails; but following their dispase tre atment, all spermatozoa were stained. The restricted staining of the a ssembled FS of maturing sperm tails indicated the late appearance of t he antigens during spermatogenesis. The antibody did not react with sp erm cell precursors or other cell types within/without the seminiferou s tubules. Untreated and dispase-treated frozen sections of skin, oeso phagus, tongue, liver, kidney, stomach, ileum or their blood vessels s howed no reaction. These data provide the first evidence for the prese nce of masked antigens within the human sperm tail FS, and their signi ficance is discussed.