Theoretical aspects of screening for high affinity monoclonal antibody to cell surface antigens

The relative affinity of the cell-antibody interaction can be determined by finding the highest titer of one reactant which binds effectively to a fixed, dilute concentration of the other. There are two ways to perform these experiments: the antibody dilution method and the cell dilution method. The antibody dilution approach requires measuring the highest antibody dilution which can react with a small, fixed concentration of cells. If the endpoint antibody concentration is small, the antibody has a high binding constant. In the cell dilution method the investigator must find the highest cell dilution which can bind a small, fixed antibody concentration. If the antibody has a high affinity constant, the endpoint cell concentration will be small. When the antibody and cell receptor concentrations are known, functional binding constants can be calculated directly from binding data using equations presented in this paper. Binding constants measured by these methods will help predict the behavior of monoclonal antibodies in immunoassays and in experiments where monoclonal antibody is injected in vivo for imaging or pharmacologic delivery.