Application of engineered chimeric antibodies to the calibration of human antibody standards.

Immunoassay quantitation of human antibody depends on the availability of reference sera that have been characterized in terms of their antibody content. This report expands upon the concept of "cross-calibration", using reference (dose-response) curves that have been generated with heterologous antibody as a means of calibrating prospective human antibody standards. Engineered human-mouse chimeric antibody, with a single human isotype and specificity, is used to construct the heterologous dose-response curve from which test antibody response data are interpolated. Transfer experiments are used to define and correct for the percentage of the total chimeric antibody that is immunoreactive and bound to solid phase antigen. The chimeric antibody-based calibration procedure is illustrated using H. influenzae Type B as the model antigen and an engineered chimeric IgG1 antibody that has a known mass per volume content and specificity for the hapten, 4-hydroxy-3-nitro-phenylacetyl (NP).