Abstract
Abstract: :
Purpose: To understand why the genes for TNFα and the anti–oxidant enzyme glutathione peroxidase (Gpx4) are highly expressed in TGFß–treated antigen presenting cells (APCs) that induce anterior chamber associated immune deviation (ACAID). Methods: Thioglycollate–elicited peritoneal exudate cells (APCs) from wild type (WT) C57BL/6 and TNFα receptor 2 (TNFR2) KO mice were treated overnight with TGFß2 (5 ng/ml) and pulsed with ovalbumin (OVA), then examined at selected times for reactive oxygen species (ROS) content by flow cytometry, and for expression of Gpx4 and IL–12 p40 by RT–PCR. IL–12 content was evaluated by ELISA in supernatants following 48 hr treatment of TGFß–treated APCs with Gpx inhibitor mercaptosuccinic acid (MS). Results: Intracellular ROS levels in WT, but not TNFR2 KO, APCs reached high levels at 18 hr, then subsided abruptly by 24 hr. Levels of mRNA for Gpx were elevated in both WT and TNFR2 KO APCs. IL–12 p40 content of supernatants was reduced in TGFß2–treated WT, but not TNFR2 KO, APCs, and this difference was enhanced in the presence of MS. Conclusions: TNFα signaling of TGFß2–treated APCs via TNFR2 profoundly inhibits IL–12 production by generating an early burst of ROS, which is then rapidly quenched by Gpx. In the absence of signaling via TNFR2 or when Gpx is inhibited, TNFα induces sustained NFkB activation,which leads to enhanced IL–12 production, thus robbing the APCs of their capacity to induce ACAID.
Keywords: ACAID • antigen presentation/processing • immunomodulation/immunoregulation