TTR and juvenile idiopathic arthritis: Serum and aqueous humor (AqH) have shown differential expression of cytokines and chemokines (e.g., interleukin-29/interferon-λ1 [IL-29/IFN-λ1], transthyretin [TTR]) in children with JIA-U [8–12]; however, the invasive nature of AqH collection precludes collection from children with JIA but no uveitis and from those who are not undergoing eye surgery.