Th17 cells contribute to the exacerbated autoimmune arthritis in CCR2-deficient mice (34.6)

Abstract

Th17 cells have been implicated in the pathogenesis of autoimmune diseases including rheumatoid arthritis (RA). Chemokine receptor CCR2 mediates leukocyte trafficking to sites of inflammation and is considered to be an important proinflammatory factor in RA. However, as an unexpected paradox, mice lacking CCR2 (CCR2-/-) develop an accelerated and enhanced arthritis in the collagen induced arthritis model (CIA). To investigate the underlying mechanism(s), we examined the role of Th17 cells in CCR2-/- mice with CIA. We found that the number of Th17 cells was increased significantly in draining lymph nodes of CCR2-/- CIA mice (845±144) compared to WT controls (289±136, p=0.017). In contrast, Th1 cells were not significantly different between groups (485±171 vs. 516±86 for WT, p=0.88). Consistently, CCR2-/- CIA mice had elevated levels of sera IL-17 (84.4±15.5 pg/ml) and IL-17 mRNA in arthritic joints (3.43±0.61 fold) compared to WT mice (45±9.7 pg/ml in the serum and 0.21±0.05 fold in the joint, p=0.04 and 0.009 respectively). Furthermore, Th17-favored cytokines IL-6 and IL-1β were up-regulated in the serum of CCR2-/- animals (IL-6: 366.1±54.5 pg/ml vs. 58.7±13.3 pg/ml for WT, p=0.0004; IL-1β: 189.6±21.9 pg/ml vs. 106.4±21.3 pg/ml for WT, p=0.01). These data suggest that Th17 cells contribute to the pathogenesis of the aggravated phenotype of autoimmune arthritis in CCR2-/- mice. Mice deficient in CCR2 may serve as a model for evaluations of anti-Th17 therapies against RA.