Estimation of association constants of 42 monoclonal antibodies to human IgG epitopes using a fluorescent sequential-saturation assay.

We measured the association constant (Ka) for 42 murine monoclonal antibodies (MAbs) to human IgG epitopes. Included are antibodies, previously evaluated in an IUIS/WHO collaborative study, to various epitopes on the four subclasses of human IgG - IgG Fc, IgG Fab, kappa, and lambda - and to selected IgG allotopes. We used a sequential-saturation immunofluorescent assay and interactive computer program to determine the Ka by Scatchard analysis. Kas ranged from unmeasurably low by this method (approximately 10(6) L/M) to 3.8 X 10(9) L/M. Some class specific MAbs had large Ka differences for different subclasses and some subclass specific MAbs had large Ka differences for molecules of the same subclass but of different light-chain types.