GIT1 is an untolerized autoantigen involved in immunologic disturbance of spermatogenesis

Male haploid cells, spermatids and spermatozoa, that appear after the establishment of immune tolerance express novel cell surface and intracellular proteins that can be recognized as foreign antigens by the self-immune system. However, these germ cells do not normally evoke a pathological immune response. The immune-privileged micro-circumstance in testis involving the blood-testis-barrier formed by Sertoli cells protects these germ cells from autoimmune attack. We recently found that immunization with heat shock protein family A member 4-like (HSPA4L), one of the new differentiation antigens of haploid cells, induced experimental autoimmune orchitis (EAO) in A/J male mice. In this study, we focused on G protein-coupled receptor kinase interacting protein-1 (GIT1), another haploid cell-specific differentiation antigen, to investigate whether GIT1 is a target autoantigen for EAO induction. GIT1 emulsified with complete Freund's adjuvant was injected subcutaneously into the mice inguinal region once on day 0 and again on day 14, and the optimum condition of EAO induction was determined. Mice immunized with 200 μg GIT1 showed significantly higher incidence of EAO than that of immunization with other concentrations. In particular, significant lymphocytic inflammation and extensive aspermatogenesis were observed in these mice at 120 days after the first immunization. These findings indicate that GIT1 is also a target antigen that induces EAO, like HSPA4L.