PDGFRA and rheumatoid arthritis: Combined with fluorescence-labeling of CTLA-4 Ig, a biological agent used for the treatment of rheumatoid arthritis, we identified that CTLA-4 Ig was distributed predominantly within the inflamed synovium and bound to CX3CR1+ macrophages and CD140a+ fibroblasts 6 h after injection, but not to mature osteoclasts.