Outer dense fiber proteins are dominant postobstruction autoantigens in adult Lewis rats

Obstruction of the male reproductive tract commonly results in generation o f antisperm autoantibodies. However, only a few of the sperm autoantigens r ecognized by these antibodies have been characterized. To identify postobst ruciton rat sperm autoantigens, sperm proteins were separated by two-dimens ional (2-D) gel electrophoresis. Spots corresponding to proteins that were stained by at least 50% of postvasectomy rat sera on 2-D Western blots were removed from polyacrylamide gels and microsequenced by tandem mass spectro metry. From a total of 21 spots, 12 contained peptides that matched solely to either of two outer dense fiber proteins, odf1 or odf2, Six additional s pots contained peptides comprising odf1 or odf2 and were accompanied by pep tides representing other proteins. Only three spots lacked outer dense fibe r peptides but did contain sequences of other known proteins. The results i ndicate that the outer dense fiber proteins odf1 and odf2 are dominant post obstruciton autoantigens because they were detected in the majority of the immunoreactive protein spots examined. Possible explanations for this obser vation include the abundance of outer dense fiber proteins in spermatozoa, slow solubility, which may provide a sustained supply of antigen, and testi s-specific expression during spermiogenesis.