OP-17 - Characterization of spontaneously-occurring self-reactive antibody to sperm and its effects on in-vitro fertilization

Abstract

Anti-sperm antibodies detected in humans possibly cause infertility. The mechanism of antibody production and the corresponding antigen are still unknown. Previously, we established a monoclonal antibody (named Ts3) reactive to sperm from an aged male mouse without any immunization. This study aims to identify the target self-antigen of Ts3 and to examine its effects on in-vitro fertilization. To examine the localization of the Ts3 recognizing antigen, mouse epididymal sperm were collected for immunofluorescent staining. The sperm proteins were extracted for two-dimensional electrophoresis and western blot analysis. Positive spots were subjected to mass spectrometry (MS). To determine influence on sperm motility, sperm immobilization test (SIT) with Ts3 was carried out. Further, the effects of Ts3 on mouse in-vitro fertilization and the developmental capacity of preimplantation embryos were investigated. Ts3 reacted to the midpiece and principal piece of mouse sperm. The detected molecular weight of the antigen to Ts3 was around 37 kDa, and the molecule was identified as outer dense fiber protein 2 (ODF2) by MS. In SIT, Ts3 was suggested to have harmful effect on sperm motility. Ts3 inhibited embryo development but not fertilization in mouse. Immunofluorescent staining of mouse preimplantation embryo showed Ts3 reacted to the membrane of the embryo and the areas of cellular contact. This study showed that Ts3, a spontaneously-occurring self-reactive antibody to sperm, recognized ODF2 as a targeted antigen. Although Ts3 did not inhibit fertilization, it impaired the sperm motility and the development of preimplantation embryo. Therefore, ODF2 antigen may be a pathogenic factor in infertility.