Biologic Activity of Aggregated γ-Globulin

Summary Aggregated human and rabbit γ-globulin fixed complement and induced skin reactions in normal guinea pigs. The aggregated γ-globulin and soluble antigen-antibody complexes were comparable on a weight basis with respect to these biologic activities. The complement fixing properties of the aggregated γ-globulin were independent of the method for aggregation, i.e., heating, mercaptoethanol-urea or coupling by bis-diazotized benzidine, but were dependent on the species from which the γ-globulin was derived. Aggregated bovine or chicken γ-globulin did not fix complement. Horse γ-globulin showed a slight increase in its anticomplementary activity on aggregation with bis-diazotized benzidine. Combination of aggregated γ-globulin with tissue constituents of the guinea pig skin was probably one of the necessary processes in the skin reaction. The mechanism for the induction of the biologic activities by the formation of aggregated γ-globulin and of antigen-antibody complexes was discussed.