Tentative identification of sex-specific antibodies and their application for screening bovine sperm proteins for sex-specificity.

Our previous studies indicated that a purified rabbit antiserum against X-sperm contained sex-specific antibodies (SSAbs) which preferentially bound to sex-sorted X-sperm. The specificity of sex-specific antiserum was initially demonstrated using flow cytometry only, which resulted in uncertainty. In this study, the putative SSAbs against bovine X-sperm (XSSAb) were produced by a series of immunological approaches, and the effectiveness of separation of sperm using putative XSSAb was validated. Subsequently, the XSSAb was used to immunoprecipitate sex-specific proteins (SSPs) in bovine sperm, followed by two-dimensional gel electrophoresis. The results showed 7.6, 15.2 and 52.1 % of sex-sorted Y-sperm, sex-sorted X-sperm and unsorted sperm were recognized by the neutralized rabbit antisera against X-sperm, respectively. Also the purity of separation of sperm using putative XSSAb reached 74.3 % when the immunologically separated sperm were injected into oocytes. In addition, three candidate SSP sports about 30 kDa were captured by the XSSAb. Our results confirmed that the putative XSSAb contained SSAbs, and implied that these three protein sports might be SSPs in bovine X-sperm. This provides a potentially more efficient method for sorting sperm and lays a foundation for future search for SSPs.