QUANTITATIVE INVESTIGATIONS OF IDIOTYPIC ANTIBODIES

Abstract

The interaction of antigen with specific, cell-associated receptors was measured in thermodynamic terms. The binding of ¹²⁵I-labeled 2,4-dinitrophenyl guinea pig albumin (DNP₁₆GPA-¹²⁵I) to lymphocytes from guinea pigs immunized to DNP₁₆GPA is a temperature-dependent, reversible process. Measurement of association and dissociation rates of antigen-receptor complexes permits calculation of antigen-cell binding constants. These may also be calculated by equilibrium-binding techniques. Although differences in the constants calculated in these two ways exist, a clear increase in avidity of cell receptor for antigen occurs in the course of the immune response. This change in receptor avidity provides evidence that the time-dependent change in affinity of serum antibody (maturation) indeed has a cellular basis.