Targeting of Gr‐1+,CCR2+ monocytes in collagen‐induced arthritis

Abstract

Objective. The chemokine receptor CCR2 is highly expressed on monocytes and considered a promising target for treatment of rheumatoid arthritis. However, blockade of CCR2 with a monoclonal antibody (mAb) during progression of collagen-induced arthritis results in a massive aggravation of the disease. In this study we investigated why CCR2 antibodies have proinflammatory effects, how these effects can be avoided, and whether CCR2؉ monocytes are useful targets in the treatment of arthritis.Methods. Arthritis was induced in DBA/1 mice by immunization with type II collagen. Mice were treated with mAb against CCR2 (MC-21), IgE, or isotype control antibodies at various time points. Activation of basophils and depletion of monocyte subsets were determined by fluorescence-activated cell sorter analysis and enzyme-linked immunosorbent assay.Results. Crosslinkage of CCR2 activated basophils to release interleukin-6 (IL-6) and IL-4. In vivo, IL-6 release occurred only after exposure to high doses of MC-21, whereas application of low doses of the mAb circumvented the release of IL-6. Regardless of the dose level used, the antibody MC-21 efficiently depleted Gr-1؉,CCR2؉ monocytes from the synovial tissue, peripheral blood, and spleen of DBA/1 mice. Activation of basophils with high doses of MC-21 or with antibodies against IgE resulted in a marked aggravation of collagen-induced arthritis and an increased release of IL-6. In contrast, low-dose treatment with MC-21 in this therapeutic setting had no effect on IL-6 and led to marked improvement of arthritis.Conclusion. These results show that depletion of CCR2؉ monocytes may prove to be a therapeutic option in inflammatory arthritis, as long as the dosedependent proinflammatory effects of CCR2 mAb are taken into account.CCR2, a chemokine (CC motif) receptor, is considered a promising target for disorders such as multiple sclerosis, type II diabetes, and rheumatoid arthritis, and Phase I and II clinical trials are currently in progress (1). Data on CCR2 expression in humans and results from studies of CCR2-deficient mice (2-4) support the blockade of CCR2 as an effective strategy in the treatment of multiple sclerosis and diabetes. In patients with rheumatoid arthritis, we and other investigators have found an increased frequency of CCR2ϩ cells in the synovial fluid and synovial tissue (5-7). In addition, increased levels of the CCR2 ligand monocyte chemoattractant protein 1 (MCP-1; CCL2) were found in patients with rheumatoid arthritis (8). Monocytes are thought to play a major role in joint destruction, and their recruitment to sites of inflammation is crucially dependent on CCR2, as shown in several murine disease models (9-12).However, thus far, data from murine models of collagen-induced arthritis do not support CCR2 as a target for treatment of rheumatoid arthritis. We have previously shown that treatment with a blocking monoDrs. Brühl, Luckow,

Important role of interleukin‐3 in the early phase of collagen‐induced arthritis

“…Due to conflicting results in studies using different models of arthritis and different strains of mast cell-deficient mice (24)(25)(26), the role of mast cells in arthritis development is currently unclear. Our data suggest that the proarthritogenic effects of IL-3 may be mediated in part by activation of basophils and are consistent with previous data demonstrating aggravation of arthritis by application of anti-IgE or anti-CCR2 antibodies, both of which are known to activate basophils (22,27).…”

“…Our interest in analyzing the contribution of IL-3 in arthritis was prompted by our recent observation of marked aggravation of collagen-induced arthritis (CIA) by activation of basophils with antibodies against IgE (22). Basophils can be activated not only by crosslinkage of surface IgE, but by other factors, especially IL-3, as well.…”

Monocytes Control Second-Phase Neutrophil Emigration in Established Lipopolysaccharide-induced Murine Lung Injury

“…To test whether the effect was specific to particular PBM subtypes, we used low doses of an anti-CCR2 monoclonal antibody (MC21) to specifically deplete CCR2 hi Gr-1 hi PBMs (26). Preliminary studies confirmed that this dose of MC21 did not lead to peripheral blood neutrophil depletion in naive mice (n ¼ 3 mice per group receiving 20 mg of MC21 or isotype control and neutrophil percentage in whole blood was analyzed the following day; P ¼ 0.7 using MannWhitney test).…”

The Critical Role of IL-15 in the Antitumor Effects Mediated by the Combination Therapy Imatinib and IL-2

“…Abs were purchased from BD Pharmingen or eBioscience. Anti-CCR2 mAb (MC21, rat IgG2a) has been provided by M. Mack (Universitätsklinikum Regensburg, Abteilung für Nephrologie, Regensburg, Germany) (13) Fluor 488 goat anti-rat IgG has been used as secondary Ab at 1/400 (Invitrogen). Immediately before FACS analysis, 4Ј,6-diamidino-2-phenylindole (Sigma-Aldrich) was added.…”