Examples of proteins that accumulated in the serum of active TB patients include C-reactive protein (CRP), haptoglobin (HPT) alpha-1-acid glycoprotein 1 (A1AGP1), complement component C9 (C9), neutrophil defensin 1 (DEF1) and serum amyloid P component (SAA2–4). Here, SAA2 is linked to tuberculosis.