Immunologische Pathomechanismen der experimentellen Autoimmun-Orchitis

Pathogenesis of Experimental-Autoimmune-Orchitis (EAO) in Rats An animal model was developed to investigate the immunological phathomechanisms of male infertility. This so called model of Experimental autoimmune orchitis (EAO) was used to evaluate the multi-factorial influences contributing to development of orchitis. In our models, EAO was induced by injection of syngeneic testicular homogenate in adjuvans in two different rat strains (Wistar/Kyoto and Lewis) to investigate the role of the genetic predeposition on the outcome of the disease. Groups of animals were killed 25, 35, 50 and 80 days after immunisation and serum and testes were collected. HE stainings were made to determine the degree of testicular damage and cell infiltration. Frozen sections were stained immunohistochemically with the mouse anti-rat monoclonal antibodies ED1 (lysosomal antigen specific to monocytes, dendritic cells and some macrophages), ED2 (resident macrophages), OX8 (CD8+ cells), R73 (**T cell receptor), CD25 (IL-2 receptor) and OX62 (dendritic cells). Immunostained cells containing a nuclear profile were quantified using stereological methods. In addition, antibodies directed against Ki-67 (proliferation marker), Ox-6 (MHCII+ cells) as well as Ox-33 and IgG/IgM (B-cells) were applied. We found a strong increase of ED1 and ED2 positive cells in the inflamed testes. In addition, for the first time a dendritic cell (Ox62) population could be detected in the rat testis, which increased substantially (430%) in EAO animals. Furthermore, we observed an accumulation of CD4, CD8 and TCR positive cells over the experimental time. Most likely, the increase of cells over time and during EAO is based on migration rather than proliferation as immune cells did not show any staining with the proliferation marker Ki-67. The key cytokines like IL-6, IL-10, TNF-a, TGF-b and MCP-1 were investigated by in-situ-hybridisation and shown to be physiological testes cytokines but also elevated during the development of EAO. Therefore they are proposed to play a role in pathogenesis of these autoimmunedisease. Serum antibodies against testicular antigens were determined using Western blot analysis. Both rat strains displayed a different reaction pattern. Generally Wistar rats showed a substantially higher responder rate than Lewis rats (87% vs 13% 80 days after immunisation), although the latter are a common model for other autoimmune diseases. Reactions of auto-antibodies were particularly strong during the early experimental phase in Wistar rats, whereas the reaction was less pronounced in the later phase when testicular damage was most prominent. In contrast, the rate of histologically proven EAO responders was constant in Lewis rats although the development of auto-antibodies increased steadily with experimental time. Auto-antigens were determined using Western blot analysis and 2D-SDS-PAGE. Proteins at a molecular weight of 84, 55 and 40 kDa were the major detected testicular auto-antigens. The differential expression of CD5, IL-7, IL-1 receptor1 and IL-8 receptor beta as determined by cDNA array analysis suggested a role for these factors during the pathogenesis of EAO. In summary pathogenesis of EAO depends on genetic predisposition as detemined by different rates and severity of EAO between different rat strains. Development of EAO is characterized by cellular infiltration, increase of cytokin expression and development of auto-antibodies.