Determination of the in vivo antigen-antibody affinity constant from the redistribution of desipramine in rats following administration of a desipramine-specific monoclonal antibody.

Quantitative expressions have been derived to determine the affinity constant for the in vivo interaction of an antigen with its elicited monoclonal antibody by analysing the redistribution of antigen following antibody administration. Using this method, the intrinsic binding constant for the interaction of subtoxic doses of DMI in rats with anti-TCA was found to be about two orders of magnitude less than the value obtained in vitro. The disparity is probably due to the presence of endogenous ligands for the antibody.