Equine antihapten antibody II. The γG(7 Sγ) components and their specific interaction

Abstract

The γG(7 Sγ) components of antibody prepared against the haptenic group p-azophenyl-β-lactoside (Lac) were isolated from equine antiserum. The average association constants ( K A) for the specific interaction of this antibody with the hapten, p-( p-dimethyl-aminobenzeneazo)-phenyl-β-lactoside (Lac dye), were determined at 25° and 37.2° by equilibrium dialysis. Thermodynamic parameters have been calculated and shown to be very similar to those previously obtained for rabbit anti-Lac antibody. A physical-chemical and immunochemical characterization of the purified γG equine anti-Lac antibody has demonstrated chromatographic, electrophoretic and antigenic heterogeneity. Three antigenically distinct immunoglobulins have been identified in the purified γG anti-Lac antibody each having antibody activity. The antigenic individuality has been related to the heavy chains when compared by immunodiffusion to one another or to γA ( β 2A) antibody from the same serum. A comparison of the binding by the γG antibody with the binding previously described for the γA antibody shows that the affinity of the latter for the Lac dye is much greater. This difference in the affinity for hapten between different immunoglobulins present in the same serum may partially explain the heterogeneity of hapten binding in purified antibody. Furthermore, variation in the relative amounts of these immunoglobulins with time after immunization could in part account for the temporal changes in the affinity of the antiserum for hapten.