The acute-phase response to tissue injury and inflammation is accompanied by a dramatic increase in the hepatic synthesis of plasma proteins known as acute-phase reactants (APRs). This response is mediated by cytokines produced in part by activated macrophages at the site of inflammation; glucocorticoids have also been implicated as playing a regulatory role. The effects of the cytokines interleukin (IL)-1 beta and -6, alone or in combination, and in the absence or presence of the synthetic glucocorticoid dexamethasone, on the levels of APR mRNAs in the human hepatoma cell line PLC/PRF/5 were analysed. The accumulation of APR mRNAs [the complement components C3, factor B and Cl inhibitor; the major APRs C-reactive protein (CRP) and serum amyloid A protein and the CRP analogue serum amyloid P protein] was determined in dose-response and time-course studies. The APRs differed from each other in their responses to IL-1 beta alone, IL-6 alone, and IL-1 beta plus IL-6. Dexamethasone enhanced the cytokine-driven induction of a subset of APR mRNAs. These studies detail the heterogeneity of the ‘in vitro’ acute-phase response to defined mediators.
