Given the extraordinary influence of T cell signaling/activation on macrophage phenotype in HRS-induced myositis and the important functional interactions between macrophages and fibroblasts in other autoimmune diseases such as scleroderma and rheumatoid arthritis (19, 20), we also assessed the transcriptional profiles of fibroblast subsets in WT, OT-II TCR transgenic, CD4-Cre.MyD88fl/fl, and RAG1 KO mice following HRS immunization. This evidence concerns the gene RAG1 and autoimmune disease.