Effects of fungal beta-glucan and interferon-gamma on the secretory functions of murine alveolar macrophages

We investigated the effect of a fungal component, soluble beta-glucan, on secretory functions of murine alveolar macrophages (AMs) in vitro. Stimulation by beta-glucan (500 mu g/mL) or interferon-gamma (IFN-gamma; 100 U/mL) alone had a slight effect on AM functions, but when AMs were incubated together with beta-glucan and IFN-gamma, the production and secretion of some immune mediators, such as nitric oxide, interleukin-1 (IL-1), 1L-6, and turner necrosis factor-alpha (TNF-alpha), were markedly augmented. This combined effect of beta-gIucan and IFN-gamma was based on a priming effect of IFN-gamma because prestimulation with IFN-gamma followed by beta-glucan induced high nitric oxide production of AMs, Lat reversal of the sequence of treatments had only a slight effect, We also found that preincubation of AMs with IFN-gamma enhanced the binding of fluorescein-labeled beta-glucan on the AM surface, and this increased binding was abrogated to the control level by the addition of three: species of soluble unlabeled (1-->3)-beta-D-glucans but not by soluble alpha-glucan, These data imply that the printing effect of IFN-gamma on the AM response to beta-glucan was dependent, at least in part, on the enhancement of beta-glucan specific binding sites on the AM surface, It was suggested that IFN-gamma is one of the principal factors controlling the pulmonary immune system against both severe fungal infection and inflammation via AM activation at the alveoli.