Transgenic mice expressing human FcγRIIa have enhanced sensitivity to induced autoimmune arthritis as well as elevated Th17 cells

The major human Fc receptor, huFc gamma RIIa, is implicated in the development of autoimmune arthritis in humans but until recently has not been studied in mouse models. We evaluated potential roles of Fc gamma RIIa by using transgenic mice expressing the receptor. We examined two models of induced autoimmune arthritis pristane-induced arthritis (PIA) and collagen-induced arthritis (CIA) as well as the anti-collagen-II antibody-induced arthritis (CAIA) model. In the induced arthritis models PIA and CIA, the transgenic mice developed a more severe arthritis than the other arthritis-prone SJL or DBA1 mice. Interestingly, anti-collagen-II antibodies were elevated in PIA in the susceptible mice. In the CIA model, the highly susceptible transgenic mouse had IgG subclass levels equivalent to the unaffected and disease resistant C57BL/6 mouse strain implying that the Fc gamma RIIa lowers the threshold of IgG dependent leukocyte activation. This is consistent with the greatly enhanced sensitivity of the Fc gamma RIIa transgenic mice to CAIA which clearly indicates a role for the receptor at least at the inflammatory effector cell level. Other roles for huFc gamma RIIa or other gene products in the development of autoimmunity cannot be ruled out however, especially as the mice exhibited elevated Th1 or Th17 CD4 T cells in the draining lymph nodes. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.