T H E Biological Activity of Soluble Antigen-antibody Complexes Ii. Physical Properties of Soluble Complexes Having Skin-irritating Actmt¥*

Previous work by Germuth and McKinnon (1), Trapani et al. (2), and ourselves (3) has established the fact that soluble antigen-antibody complexes formed in excess antigen can, (a) induce symptoms similar to anaphylaxis, (b) cause contraction of isolated smooth muscle from normal guinea pigs, and (c) increase the permeability of skin capillaries in a manner similar to that obtained in passive cutaneous anaphylaxis. These findings immediately raise many questions as to the fundamental mechanisms involved. For example, is the free antigen playing some role; is the toxicity dependent upon some change in the molecular structure of either antigen or antibody upon combination; is the complex itself toxic without any change in the molecular structure of the components; is the antigen-antibody ratio important; and, is complement involved? The work reported here involves a study of the possible role of free antigen and the nature of the complex. Some study was also made of untreated a n d decomplemented antiserums and, although there was no difference, this cannot rule out the possible participation of the test animal's (guinea pig's) own complement.