Brühl Hilke, Cihak Josef, Plachý Jirí, Kunz-Schughart Leoni, Niedermeier Marianne, Denzel Andrea, Rodriguez Gomez Manuel, Talke Yvonne, Luckow Bruno, Stangassinger Manfred, Mack Matthias
Regensburg University Medical Center, Regensburg, Germany.
Arthritis Rheum. 2007 Sep;56(9):2975-85. doi: 10.1002/art.22854.
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.
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.
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.
These results show that depletion of CCR2+ monocytes may prove to be a therapeutic option in inflammatory arthritis, as long as the dose-dependent proinflammatory effects of CCR2 mAb are taken into account.
趋化因子受体CCR2在单核细胞上高度表达，被认为是类风湿关节炎治疗的一个有前景的靶点。然而，在胶原诱导的关节炎进展过程中用单克隆抗体（mAb）阻断CCR2会导致疾病的大规模加重。在本研究中，我们调查了CCR2抗体具有促炎作用的原因、如何避免这些作用，以及CCR2+单核细胞是否是关节炎治疗的有用靶点。
用II型胶原免疫DBA/1小鼠诱导关节炎。在不同时间点用抗CCR2的mAb（MC-21）、IgE或同型对照抗体治疗小鼠。通过荧光激活细胞分选分析和酶联免疫吸附测定法测定嗜碱性粒细胞的活化和单核细胞亚群的耗竭情况。
CCR2的交联激活嗜碱性粒细胞释放白细胞介素-6（IL-6）和IL-4。在体内，仅在暴露于高剂量的MC-21后才发生IL-6释放，而应用低剂量的mAb可避免IL-6的释放。无论使用的剂量水平如何，抗体MC-21都能有效地从DBA/1小鼠的滑膜组织、外周血和脾脏中清除Gr-1+、CCR2+单核细胞。用高剂量的MC-21或抗IgE抗体激活嗜碱性粒细胞会导致胶原诱导的关节炎明显加重和IL-6释放增加。相比之下，在这种治疗环境中用低剂量的MC-21治疗对IL-6没有影响，并导致关节炎明显改善。
这些结果表明，只要考虑到CCR2 mAb的剂量依赖性促炎作用，清除CCR2+单核细胞可能被证明是炎症性关节炎的一种治疗选择。
