THE 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 our-selves (3) has established the fact that soluble antigen-antibody complexes formed in excess antigen can, (a) induce symptoms imilar 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 combina-tion; is the complex itself toxic without any change in the molecular structure of the components; is the antigen-antibody ratio important; and, is comple-ment 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 and decomplemented antiserums and, although there was no dif-ference, this cannot rule out the possible participation of the test animal's (guinea pig's) own complement. EXPERIMENTAL General Procedures Antlgens.--The work to be reported here deals for the most part with bovine serum albumin (BSA) (Armour's crystallized). In order to determine antigen-antibody ratios in some of the experiments, samples of BSA were tagged with SaS-sulfanilic a id. The method of coupling and purification have be n described by Garvey and Campbell (4).As a final stage in puri: fication the S~-BSA was developed on a starch block by electrophoresis and the material ob-tained from a 4 cm. area at the zone of maximum protein concentration was used for the immunochemical studies. The final preparation contained 1.8 sulfanilic groups per molecul