CX3CL1 and rheumatoid arthritis: Based on CX3CL1 association with WHO group 1 PAH [12], its injurious role described in rodent bleomycin induced acute lung injury and pulmonary fibrosis, and its strong association with other chronic inflammatory fibroproliferative diseases such as rheumatoid arthritis, Sjogren’s disease, and systemic lupus erythematosus [13], we hypothesized that the CX3CR1/CX3CL1 axis may be involved in the pathogenesis of SSc associated pulmonary diseases.