CRP and bacterial infectious disease: Conversely, the absence of a significant increase of IL-6 at day 270 probably explains why, despite increased levels of haptoglobin, α-1 acid glycoprotein, C3 and C4, and ceruloplasmin in patients with AE, no increase of C-reactive protein (CRP) levels, typically associated with IL-6 stimulation, is usually observed, except in cases complicated by bacterial infection.