Comparison of HRS-induced myositis in WT versus CD4-Cre.MyD88fl/fl conditional KO mice demonstrates significant reduction in the severity of myositis (Figure 2A) that reflects diminished infiltration of both CD3+CD4+ T cells and CD3-CD4-CD45+ non-lymphoid cells that include CD68+ macrophages (Figures 2B, C; Supplementary Figure 3). Here, PTPRC is linked to myositis disease.