CRP and thromboangiitis obliterans: In addition, TAO differs from many other types of vasculitis in that the usual immunologic markers—elevation of acute-phase reactants such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), circulating immune complexes, and autoantibodies such as antinuclear antibody, rheumatoid factor, and complement levels are usually normal or negative.