IL-6 is a cytokine with pleiotropic biological functions, including induction of the hepatic acute phase response and differentiation of activated B cells into Ig-secreting plasma cells. We found that human peripheral blood monocytes express the IL-6-R, which is undetectable on the large majority of lymphocytes of healthy individuals. Stimulation of monocytes by endotoxin or IL-1 causes a rapid downregulation of IL-6-R mRNA levels and a concomitant enhancement of IL-6 mRNA expression. IL-6 itself was found to suppress the IL-6-R at high concentrations. A gradual decrease of IL-6-R mRNA levels was observed along in vitro maturation of monocytes into macrophages. We show that downregulation of IL-6-R mRNA levels by IL-1 and IL-6 is monocyte specific, since IL-6-R expression is stimulated by both IL-1 and IL-6 in cultured human primary hepatocytes. Our data indicate that under noninflammatory conditions, monocytes may play a role in binding of trace amounts of circulating IL-6. Repression of monocytic IL-6-R and stimulation of hepatocytic IL-6-R synthesis may represent a shift of the IL-6 tissue targets under inflammatory conditions.
Regulation of interleukin 6 receptor expression in human monocytes and monocyte-derived macrophages. Comparison with the expression in human hepatocytes.
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J Bauer, T M Bauer, T Kalb, T Taga, G Lengyel, T Hirano, T Kishimoto, G Acs, L Mayer, W Gerok; Regulation of interleukin 6 receptor expression in human monocytes and monocyte-derived macrophages. Comparison with the expression in human hepatocytes.. J Exp Med 1 November 1989; 170 (5): 1537–1549. doi: https://doi.org/10.1084/jem.170.5.1537
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