Glatiramer acetate treatment directly targets CD11b+Ly6G- monocytes and enhances the suppression of autoreactive T cells in experimental autoimmune encephalomyelitis

Abstract

Glatiramer acetate (GA) is used for the treatment of relapsing-remitting multiple sclerosis (MS) and can suppress experimental autoimmune encephalomyelitis in animals. Effective GA treatment is associated with the induction of anti-inflammatory TH2 responses and antigen-specific expansion of CD25+/Foxp3+ Tregs through the modulation of antigen-presenting cells. Here, we show that intravenous injection of fluorochrome-labelled GA resulted in rapid and specific binding of GA to CD11b+ F4/80lo Ly6G- blood monocytes via an MHC class II-independent mechanism. Intravenous GA treatment enhanced the intrinsic capability of these monocytes to directly suppress T cell proliferation in vitro. The suppressive function correlated with reduced proliferation of myelin-specific T cells in vivo after intravenous GA treatment. In contrast, subcutaneous treatment with GA inhibited the pro-inflammatory IFNγ-producing T cell phenotype rather than suppressing T cell proliferation. These data indicate that (1) GA engages directly with circulating monocytes to induce type II monocyte suppressor function; and (2) the therapeutic efficacy of GA may be expanded by employing different routes of GA administration to engage alternative mechanisms of suppression of autoreactive T cells in MS. © 2011 The Authors. Scandinavian Journal of Immunology © 2011 Blackwell Publishing Ltd.