Using biosamples from oligo JIA patients, we will study the interactions between immune cells found in the joint with a focus on T cells and B cells. T peripheral helper (Tph) cells help B cells to mature and produce antibodies in inflamed tissues. Our preliminary results show that Tph cells are expanded in the joints of children with oligo JIA. To further investigate Tph cells, we will conduct experiments to determine if this immune cell population has become overly activated, promoting B cells to produce autoantibodies that drive chronic arthritis. We will also determine if there are other subsets of T cells that can counterbalance Tph cells and inhibit their activity. Through our research, we may better understand factors that cause arthritis in oligo JIA and identify novel strategies to treat children with this disease. Our ultimate goal is to improve outcomes for children with oligo JIA.