The present invention relates to the field of therapeutic antibodies. It especially relates to the study of therapeutic antibodies in an experimental animal. The present invention discloses a method of detecting a therapeutic antibody in a sample obtained from an experimental animal comprising the steps of a) providing the sample to be analyzed, b) incubating said sample with an antibody binding to a therapeutic antibody and not binding to the immunoglobulin of said experimental animal, c) optionally incubating said sample with a reagent appropriate for the selective detection of total, active or antigen-bound therapeutic antibody, and d) correlating the complex formed in (b) or (c) to the concentration of said therapeutic antibody. A monoclonal antibody directed to a certain epitope that is present on all classes of human immunoglobulin of class G, but not on the immunoglobulin of any experimental animal except on the IgG of chimpanzees was used (MAB-M-R10Z8E9).