Failure of hydrocortisone to suppress the interferon-gamma-induced augmentation of interleukin 1 secretion of aged human monocytes.

The combined effect of hydrocortisone (HC) and interferon-gamma and -alpha (IFN-gamma and -alpha) on human blood monocytes (Mo) interleukin 1 (IL 1) secretion was investigated. IL 1 was generated by treating the fresh or aged Mo with lipopolysaccharide (LPS), and quantitated by radioimmunoassay (RIA). Hydrocortisone, at the pharmacological attainable concentration of 10(-5) molar (M), markedly suppressed fresh Mo IL 1 secretion but had no effect at lower tested doses. Addition of IFN-gamma enhanced the IL 1 secretion of fresh Mo; however, the simultaneous addition of 10(-5) M HC and IFN-gamma resulted in marked suppression of the monokine release. Monocytes, when cultured in vitro for three days, lost the capacity to secrete IL 1. The loss of IL 1 secretory potential of aged Mo was prevented by preincubating them with IFN-gamma prior to LPS stimulation. IFN-alpha was ineffective in this regard. Aged Mo, pretreated with the combination of IFN-gamma and HC were still able to secrete abundant quantities of IL 1, demonstrating the failure of HC to suppress the IFN-gamma-induced augmentation of IL 1 secretory potential. Even suprapharmacologic doses of HC (10(-4) M) did not inhibit this enhancement and actually further augmented it. Thus, therapeutic concentrations of HC suppress IL 1 secretion of fresh Mo even in the presence of IFN-gamma; however, therapeutic or suprapharmacologic concentrations of HC do not inhibit the IL 1 secretory capacity of IFN-gamma-treated aged Mo.