MYD88 and myositis disease: While these results do not prove that HRS directly engages TLRs or other innate immune receptors expressed in muscle-infiltrating T cells, the development of florid myositis in HRS-immunized IL-1 Receptor KO mice (Supplementary Figure 4) suggests that phenotypic alterations in CD4-Cre.MyD88fl/fl conditional KO mice are not simply driven by reduced MyD88-dependent responses to cytokines elaborated by other cell types such as macrophages or dendritic cells.