Fatal anaphylaxis-like reaction induced by yeast mannans in nonsensitized mice.

Some yeast mannans increased vascular permeability and caused anaphylaxis-like reactions, fatal in some cases, in nonsensitized CFW mice. In SWR mice deficient in the complement system component C5, anaphylactic shock did not develop after the injection of mannans but was readily induced by goat serum after the mice had been sensitized with Bordetella pertussis and goat serum. The observed biological activity of the yeast mannans appears to depend upon the alpha(1 --> 2) and alpha(1 --> 6) linkages in their main chain. Their relative inactivity in C5-deficient mice and the consumption of whole hemolytic complement after their addition to normal mouse serum suggest that yeast mannans may activate late-acting complement components to produce anaphylatoxin from complement components C5 and C3.