The antigen-antibody reaction. III. Theoretical considerations concerning the formation, location, and curvature of the antigen-antibody precipitation zone in agar diffusion plates, and a method for the determination of diffusion coefficients of antigens and antibodies.

Abstract

Summary 1.Some aspects of the antigen-antibody reaction in agar diffusion plates were studied. 2.A method was developed that permits the prediction of whether a zone of precipitation will form for given initial amounts of antigen and antibody. Calculated values were found to agree with experimental observations. 3.An expression was obtained for the relation between the location of the zone of precipitation between antigen and antibody reservoirs and the time required for the appearance of the zone. Calculated values were found to agree with experimental observations. 4.The relationship between diffusion coefficients of antigen and antibody and the curvature of the zone of precipitation was determined. 5.Theoretical derivations of expressions for the determination of diffusion coefficients of antigens and antibodies are presented. Diffusion coefficients of human serum albumin, bovine plasma albumin and chicken ovalbumin and homologous rabbit antibodies were determined. Values were found to be in reasonable agreement with diffusion coefficients of antigens and antibodies determined by other methods. The outstanding property of this method for the determination of diffusion coefficients is its experimental simplicity.