Antibodies to DNP, DNP-glycylglycylglycine and DNP-p-aminobenzoylglutamate.

The antibodies to a series of three dinitrophenyl (DNP) derivatives of increasing site-filling capacity (DNP; DNP—glycylglycylglycine and DNP—-aminobenzolylglutamate) have been isolated in order to assess the effect of the molecular dimensions of a haptenic group on the diversity of the immune response. A decrease in both the intensity and first appearance of precipitable antibody associated with an increase in molecular size of the hapten was observed. In a 5-week interval, the affinity constant for the homologous hapten of anti-DNP—BGG antibody increased approximately 100-fold. In the same interval, the affinity of anti-DNP—glycylglycylglycine—BGG antibodies changed only three- to four-fold and no change in the affinity constant was observed for the anti-DNP—-aminobenzolyglutamate—BGG antibodies. There were no significant differences in the structural heterogeneity of the antibodies to the three haptens as measured by micro-isoelectric focusing. These observations suggest that temporal variations in binding affinity decreases as the site-filling capacity of the antigeneic determinant increases, thereby restricting the number of ways the determinant can orient itself in the combining site. It would appear that variations in antibody affinity are not indicative of antibody structural heterogeneity.