Partial loss of immunological tolerance in CCR5-deficient mice in the murine model of concanavalin A-induced liver injury

Introduction: Injection of a sublethal dose of concanavalin A (ConA) induces tolerance against the same agent within one week. Both Tregs and Th1 polarized as well as NKT cells express the chemokine receptor CCR5 and are recruited into the liver by the ligands CCL3/4/5. In this study, the role of CCR5 was investigated during ConA hepatitis and ConA tolerance induction. Methods: C57BL/6 wt and CCR5KO mice were injected with a sublethal dose of ConA or saline and restimulated with ConA after one week. Eight hours after ConA rechallenge, plasma transaminase activities and expression of cytokines and CCR5 ligands were determined. FACS analyses were performed to characterize the intrahepatic cell composition in wt and CCR5KO mice. Moreover, primary hepatocytes were isolated 2h upon ConA challenge in order to determine the expression of CCL3/4/5. Results: FACS analyses showed a reduced frequency of NK/NKT cells in naïve CCR5KO mice. Nevertheless, CCR5KO mice were more susceptible to ConA hepatitis. Furthermore, primary hepatocytes were identified as source of CCR5 ligands upon ConA challenge. Interestingly, upregulation of intrahepatic CCL5 expression persisted for several hours in ConA-treated wt mice, whereas CCL3 and CCL4 expression rapidly turned to basis level suggesting a selective role of CCR5-CCL5 interaction during liver injury. Moreover, tolerance induction by ConA was alleviated in CCR5KO mice compared to wt mice. However, CXCR3+ Tregs were still abundant in the liver of both ConA-pretreated wt and CCR5KO mice suggesting a compensatory role of CXCR3 in CCR5KO mice. Conclusion: Partial loss of ConA tolerance in CCR5KO mice suggests an involvement of CCR5-expressing cells in tolerance induction during organ-specific immune-mediated disease. Further studies are intended to identify the role of CCR5+ Tregs and of the compensatory chemokine receptor CXCR3 regarding migration, conversion and immunosuppressive capacity following an inflammatory Th1 response.

CCR5 - Tregs - concanavalin A