CD4 and juvenile idiopathic arthritis: We decided to use the immunoSEQ platform (Adaptive Biotechnologies) (16, 17) to perform high-throughput TCR repertoire analysis of CD4+ T cell subsets in JIA patients (Fig. 1), because this platform can use genomic DNA as a template and has been successfully used by other groups to address TCR repertoires in health and disease (12, 21).