Flow Cytometric Evaluation of the Therapeutic Potential of Monoclonal Antibodies to Human Lymphocytes

AbstractWith the introduction of the antibody-producing hybridoma technology, selective elimination of distinct normal or malignant lymphocyte subsets became a realistic therapeutic possibility. The experiences of the last five years have shown, however, that the achievable in vivo depletion efficiency is not satisfactory with most monoclonal antibodies used so far. Insufficient activation of human complement and/or cellular effector mechanisms as well as antibody-induced antigenic modulation seem to be mainly responsible for the observed inefficiencies. Labeled-antibody technology together with flow cytometry can be used for the in vivo evaluation of these antibody qualities. Suitable screening procedures are described and anti-lymphocyte antibody combinations with high lytic capacity with human complement and with low or absent antigen modulation are presented. Also shown is the fact that certain antibodies, such as our anti-T3 antibody, VIT3, that cannot achieve cytolysis with human complement can nevertheless induce activation of the human complement cascade and coating of target cells with C3.