Interleukin‐6 is the major regulator of acute phase protein synthesis in adult human hepatocytes

The three monokines interleukin‐1β (IL‐1β), tumor necrosis factor α (TNFα), and interleukin‐6 (IL‐6) modulate acute phase plasma protein synthesis in adult human hepatocytes. Only IL‐6 stimulates the synthesis of the full spectrum of acute phase proteins as seen in inflammatory states in humans, i.e. synthesis and secretion of C‐reactive protein, serum amyloid A, fibrinogen, α1‐antitrypsin, α1‐antichymotrypsin and haptoglobin are increased while albumin, transferrin and fibronectin are decreased. IL‐1β as well as TNFα, although having a moderate effect on the positive acute phase proteins and inhibiting the synthesis of fibrinogen, albumin and transferrin, fail to induce serum amyloid A and C‐reactive protein. These data suggest that IL‐6 plays the key role in the regulation of acute phase protein synthesis in human hepatocytes.