α 2Macroglobulin-proteinase complexes stimulate prostaglandin E2 synthesis by peritoneal macrophages

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Abstract
α2Macroglobulin is a proteinase inhibitor which is converted from its native form into an electrophoretically “fast” form by reaction with a proteinase or methylamine. All α2M “fast” forms bind to a specific high-affinity receptor on macrophages. α2M “fast” forms inhibit the interferon-γ (IFN)-induced increase in macrophage Ia expression. This study examined whether α2M-proteinase complexes alter prostaglandin (PG) E2 synthesis, and whether PGE2 mediates α2M “fast” forms effects on macrophage Ia expression. Culture with α2M “fast” forms increased PGE2 accumulation in the medium over control values in a dose-dependent manner. Culture with IFN alone did not increase PGE2 levels, but potentiated the effect of α2M-proteinase complexes on PGE2 levels. Inhibition of PGE2 synthesis did not alter the PGE2 did suppress IFN-induced Ia expression. Thus, α2M-proteinase complexes increase macrophage PGE2 synthesis, but increased synthesis of PGE2 or other cyclooxygenase products is not the mediator of antagonism of IFN-induced Ia expression by α2M-proteinase complexes.