AJ-FS1 monoclonal antibody detects a novel group of non-glycosylated antigens within the human sperm tail fibrous sheath.

AJ-FS1 is one of a new series of monoclonal antibodies (MoAbs) raised by immunizing mice with isolated human sperm tail fibrous sheath. Using indirect immunofluorescence (IIF), the AJ-FS1 MoAb did not react with the surface antigens of viable sperm, but did stain the flagellar principal piece of sperm dried onto slides or those demembranated with 1% Triton X-100. The specificity of the antibody for the fibrous sheath was confirmed by immunogold electron microscopy which showed the distribution of gold particles on the outer fibrous sheath surface, and its reaction with the Western blots of purified fibrous sheath preparations where multiple protein bands with mol. wt ranging between 97 and 28 kDa were identified. The same peptides were also detected in urea-dithiothreitol (DTT) fraction of sequentially extracted spermatozoa but not in Triton or Triton--DTT sperm lysates. The failure of sodium metaperiodate to abrogate the antibody reaction in both Western blotting and IIF indicated the non-glycosylated nature of the antigens. IIF screening of human testicular cryostat sections with AJ-FS1 MoAb showed its reactivity with the assembled fibrous sheath of maturing sperm tails only; thus indicating the late appearance of the antigens during spermatogenesis. The antibody did not react with skin, oesophagus, tongue, liver, kidney, placenta, uterus, cervix or their blood vessels. The significance of these results is discussed together with the importance of AJ-FS1 MoAb as a specific probe for the characterization of the fibrous sheath antigens in both normal and abnormal flagella.