FcγRIII‐Expressing Macrophages are Essential for Development of Collagen‐Induced Arthritis

• Published in: Scandinavian journal of immunology 2006-04, Vol.63 (4), p.282-289
• Main Authors: Andrén, M., Xiang, Z., Nilsson, G., Kleinau, S.
• Format: Article
• Language: English
• ISSN: 0300-9475; 1365-3083
• DOI: 10.1111/j.1365-3083.2006.01743.x

IgG‐binding Fc receptors, and in particular FcγRIII, are crucial for induction of collagen‐induced arthritis (CIA), as FcγRIII‐deficient mice are highly protected to arthritis. However, which of the FcγRIII‐expressing cells that is responsible for induction of arthritis is not known. In this study, we have addressed this question by purifying different FcγRIII+ cell populations, transferred them to FcγRIII‐deficient mice and studied if the recipient mice can develop arthritis. The cell populations were isolated from spleen, bone marrow and the peritoneal cavity. Our results show that FcγRIII+ CD11b+ peritoneal macrophages can render FcγRIII‐deficient mice susceptible to CIA. In contrast, FcγRIII– peritoneal macrophages or FcγRIII+ spleenocytes, bone marrow cells, mast cells or monocytes could not mediate this effect. To further evaluate the contribution of the FcγRIII+ macrophages in arthritis, we investigated the cytokine profile in these cells during CIA. The arthritic macrophages exhibited significantly higher mRNA levels of TNFα and IL‐12p35 compared with macrophages from normal mice. We conclude that FcγRIII‐expressing macrophages, producing pro‐inflammatory cytokine and T helper type 1 differentiating factor, are the major effector cells in the induction of CIA.