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Objective: To assess the preclinical efficacy and mechanism of action of an anti-CX 3 CL1 monoclonal antibody (mAb) in systemic sclerosis (SSc)., Methods: Cultured human dermal fibroblasts were used to evaluate the direct effect of anti-CX 3 CL1 mAb on fibroblasts. In addition, bleomycin-induced and growth factor-induced models of SSc were used to investigate the effect of anti-CX 3 CL1 mAb on leukocyte infiltration, collagen deposition, and vascular damage in the skin., Results: Anti-CX 3 CL1 mAb treatment significantly inhibited Smad3 phosphorylation (P < 0.05) and expression of type I collagen and fibronectin 1 (P < 0.01) in dermal fibroblasts stimulated with transforming growth factor β1 (TGFβ1). In the bleomycin model, daily subcutaneous bleomycin injection increased serum CX 3 CL1 levels (P < 0.05) and augmented lesional CX 3 CL1 expression. Simultaneous administration of anti-CX 3 CL1 mAb or CX 3 CR1 deficiency significantly suppressed the dermal thickness, collagen content, and capillary loss caused by bleomycin (P < 0.05). Injection of bleomycin induced expression of pSmad3 and TGFβ1 in the skin, which was inhibited by anti-CX 3 CL1 mAb. Further, the dermal infiltration of CX 3 CR1+ cells, macrophages (inflammatory and alternatively activated [M2-like] subsets), and CD3+ cells significantly decreased following anti-CX 3 CL1 mAb therapy (P < 0.05), as did the enhanced skin expression of fibrogenic molecules, such as thymic stromal lymphopoietin and secreted phosphoprotein 1 (P < 0.05). However, the treatment did not significantly reduce established skin fibrosis. In the second model, simultaneous anti-mCX 3 CL1 mAb therapy significantly diminished the skin fibrosis induced by serial subcutaneous injection of TGFβ and connective tissue growth factor (P < 0.01)., Conclusion: Anti-CX 3 CL1 mAb therapy may be a novel approach for treating early skin fibrosis in inflammation-driven fibrotic skin disorders such as SSc., (© 2019, American College of Rheumatology.)

Chemokine systems modulate inflammatory and immune responses in inflammatory bowel disease (IBD). The colons of IBD patients show increased levels of fractalkine (FKN) and high numbers of FKN receptor-positive (CX3CR1+) cells; however, the FKN-CX3CR1 axis's role in intestinal inflammation, especially in intravascular leukocyte behaviors, still remains unclear. Here, we show that interruption of the FKN-CX3CR1 axis by anti-FKN monoclonal antibody (mAb) ameliorates murine colitis through regulation of intravascular monocyte behaviors in murine colitis models. FKN expression was detectable in vascular endothelium and CX3CR1+ macrophages accumulated in the mucosal lamina propria and submucosa of the inflamed colons. CD115+ monocytes tethered to the venous endothelium and expressed pro-inflammatory mediators. The anti-FKN mAb improved colitis symptoms, markedly reduced pro-inflammatory factors in the colon, maintained blood vessel integrity and reduced tethered monocytes in the inflamed veins. Intravital imaging revealed that CD115+Gr-1low/- monocytes crawled on the apical surfaces of venous endothelium, and anti-FKN mAb rapidly dislodged the crawling monocytes and inhibited their patrolling behavior. These findings suggest that the FKN-CX3CR1 axis triggers the patrolling behavior of crawling monocytes on the venous endothelium of inflamed colons, and accelerates the subsequent leukocyte activation and infiltration by locally producing inflammatory cytokines and chemokines. The mAb also ameliorated symptoms in another IBD model, T-cell-transferred colitis. Blocking the FKN-CX3CR1 axis with an anti-FKN mAb considerably inhibits the colitis-triggered inflammatory cascades, which may be an alternative strategy to treat IBD., (© The Japanese Society for Immunology. 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objective: To elucidate the role of the fractalkine (FKN)/CX 3 CR1 pathway in joint destruction in rheumatoid arthritis., Methods: We examined the effect of treatment with anti-mouse FKN (anti-mFKN) monoclonal antibody (mAb) on joint destruction and the migration of osteoclast precursors (OCPs) into the joint, using the collagen-induced arthritis (CIA) model. DBA/1 mice were immunized with bovine type II collagen to induce arthritis, and then treated with anti-mFKN mAb. Disease severity was monitored by arthritis score, and joint destruction was evaluated by soft x-ray and histologic analyses. Plasma levels of joint destruction markers were assessed by enzyme-linked immunosorbent assay. FKN expression on endothelial cells was detected by immunohistochemistry. Bone marrow-derived OCPs were labeled with fluorescein and transferred to mice with CIA, and the migration of the OCPs to the joints was then analyzed., Results: Both prophylactic and therapeutic treatment with anti-mFKN mAb significantly decreased the arthritis and soft x-ray scores. Plasma levels of cartilage oligomeric matrix protein and matrix metalloproteinase 3 decreased after treatment with anti-mFKN mAb. Histologic analysis revealed that anti-mFKN mAb inhibited synovitis, pannus formation, and cartilage destruction, as well as suppressed bone damage, with a marked reduction in the number of tartrate-resistant acid phosphatase-positive osteoclasts. Anti-mFKN mAb strongly inhibited the migration of bone marrow-derived OCPs into the affected synovium., Conclusion: Anti-mFKN mAb notably ameliorates arthritis and joint destruction in the CIA model, as well as inhibits migration of OCPs into the synovium. These results suggest that inhibition of the FKN/CX 3 CR1 pathway could be a novel strategy for treatment of both synovitis and joint destruction in rheumatoid arthritis., (2018, American College of Rheumatology.)