IN RA: IgA-RF seen in 50%, IgA-ACPA in 20-40% (& are very specific). IgA-RF or -ACPA found in serum, saliva & syn.fluid.& may underlie "mucosal hypothesis" of RA. IgA-RF assoc w/ more severe RA, worse outcomes, Xtra-articular manifestations, & blunted TNF inhibitor responses https://t.co/SVUJmrIy2F