Unique promotion of erythrophagocytosis by malondialdehyde

Modification of the normal erythrocyte membrane by reagent malondialdehyde (MDA) promotes phagocytosis of red blood cells by human macrophages, a phenomenon previously shown to involve both IgG-dependent and IgG-independent mechanisms and to be demonstrable even at micromolar MDA concentrations. In the present studies, we demonstrate this effect using 1mM MDA prepared both by acid hydrolysis of malonaldehyde bis-(dimethyl acetal) and by enzymatic synthesis from 1,3-propanediol. Remarkably, we find that equimolar amounts of other mono- and dialdehydes fail to promote erythrophagocytosis despite similarity to MDA in size and structure and ability to cross link. Authentic MDA seems to be unique among small aldehydes in ability to promote erythrophagocytosis at low aldehyde concentration and, therefore, has a special biologic relevance among the great variety of peroxidation byproducts.