A non-classical type of alveolar macrophage response to Trichinella spiralis infection

Studies of arginase expression and activity in guinea pig alveolar macrophages during Trichinella spiralis infection, prompted by earlier observation of innate lung response to the parasite, showed the macrophages to express both activity and protein of arginase type I. In cultured macrophages part of the enzyme was found to be always released to the extracellular medium. Whereas BCG in vivo treatment, alone or preceded by T. spiralis infection, stimulated arginase activity, T. spiralis infection alone affected the enzyme distribution between intracellular and extracellular fractions, and properties (K-m and V-max), rather than total (intracellular + extracellular) activity, with TGF-beta apparently responsible for a part of the effect. Anti-TGF-beta antibody treatment of the animals influenced both arginase activation by Mn2+ and dependence of the enzyme-catalysed reaction on pH. Whereas T. spiralis infection activated guinea pig alveolar macrophages by the type II macrophage activation, as indicated by constant arginase expression, associated with previously demonstrated lack of stimulation of nitric oxide production, BCG treatment invoked an alternative type of activation mechanism, reflected by stimulation of macrophage arginase, but not iNOS, activity.