Increased T Cell Plasticity With Dysregulation of Follicular Helper T, Peripheral Helper T, and Treg Cell Responses in Children With Juvenile Idiopathic Arthritis and Down Syndrome-Associated Arthritis.

DA is more common and more aggressive than JIA. It is characterized by increased polyreactive Th, Tfh, and Tph cell responses, reduced Treg cell frequency, and evidence of increased synovial inflammation, all of which are potentially distinct from JIA and T21.