Rheumatoid arthritis (RA) afflicts millions globally, causing significant joint deformity, pain, and functional disability. RA is without cure and its cause is unknown, but CD4 T cells—immune cells widely accepted to play a key role in RA pathogenesis—from patients with RA become activated by proteins through their T cell receptor (called “antigen-specific T cells”) and cause arthritis. Dr. Ashouri’s research uses a unique tool to identify and characterize these antigen-activated T cells in both a mouse model of RA and human RA. Elucidating the contribution of these pathogenic CD4 T cells to arthritis development in RA holds promise for the discovery of improved therapeutic targets.