Dendritic Cell Based Intervention Effectively Prevents the Development of Experimental Autoimmune Orchitis in Rats.

Abstract

In recent years, dendritic cells (DC) have received increasing attention as key players in both, the initiation and maintenance of autoimmune disease and the induction of peripheral tolerance. The maturation and/or activation state of DC is regarded as a control point for the induction of either peripheral tolerance or autoimmunity. Especially immature or semi-mature DC have a potent ability to tolerize T cells and prevent undesired immune reactions. Immature DC have the highest capacity to internalize antigens, but low T cell stimulatory activity, whereas mature DC downregulate their endocytic activity and are excellent T lymphocyte stimulators. Infection and inflammation of the male genital tract are amongst the most important identifiable etiologies of infertility and experimental autoimmune orchitis (EAO) serves as a model to study chronic testicular inflammation and organ specific autoimmunity. The histopathology of EAO is characterized by a substantial increase of interstitial lymphocytes and macrophages, different degrees of germ cell loss caused by apoptosis resulting in aspermatogenesis and atrophy of the seminiferous tubules. Our recent characterization of the testicular autoantigens heat shock protein 70 (hsp70) and heteronuclear ribonucleoprotein H1 (hn RNP H1) in EAO animals as well as the isolation and characterization of rat testicular DC prompted us to explore the potential of DC in inducing tolerance to EAO development. DC precursor cells were isolated from the bone marrow of inbred Wistar rats and differentiated in vitro to immature DC by addition of granulocyte-monocyte-colony stimulating factor (GM-CSF) and interleukin (IL)-4 to the culture medium. After 7 days in culture DC were pulsed either with the recombinant autoantigens hsp70, hn RNP H1, whole testicular homogenate or left unpulsed. DC were injected s.c. 4 weeks prior induction of EAO using testicular homogenate in adjuvant. Disease progression was intermittantly monitored using flat-panel volumetric computerized tomography (fpvCT) and by histological examination 80 days after injection of DC (50 days after EAO induction). In vivo injection of unpulsed DC showed a strong inhibitory effect on EAO development with only 33% of rats revealing signs of disease in comparison to control (100% EAO). DC pulsed with hsp70, hn RNP H1 and testicular homogenate proved to be less effective than unpulsed immature DC (66% of diseased animals). Significantly elevated levels of the anti-inflammatory cytokine IL-10 in the supernatants of isolated T cells from the spleen of rats injected with unpulsed DC point to a Th2 response which could be an explanation for the effective induction of tolerance by this cell based immunization.