House dust allergen activates the classical complement pathway in mouse serum

A house dust fraction was tested for complement activation in mouse serum using a microtitre complement fixation assay. It was observed that the preparation was a potent activator of the classical, but not of the alternative pathway suggesting an analogy with the complement activation in human serum. The activation showed similarity with that by classical complement activators such as aggregated IgG, DNA, lipopolysaccharide (LPS), but some discrepancy with mite allergen was observed. The contamination of the preparation with LPS was negligible and could not account for the anticomplementary effect. The role of DNA fragments in the activation of mouse complement by the house dust fraction is discussed. Our results suggest that the mouse is suited to study the role of complement activation by house dust constituents in the induction of the IgE response.