Two simple and rapid methods to detect monoclonal antibodies with identical epitope specificities in a large population of monoclonal antibodies.

Two novel and simple methods have been developed for detecting monoclonal antibodies (MAbs) with identical epitope specificities from a large population of MAbs against human chorionic gonadotropin (hCG). The first method was based on the observation that following radioiodination many molecules of an antigen are altered in such a manner that they cannot be recognized by MAbs. The proportion of radiolabelled antigen (Bmax) able to bind to a MAb was characteristic of that MAb and MAbs having identical specificities showed identical Bmax values. Using this principle it was possible to identify MAbs having identical epitope specificities within a large population of MAbs against hCG. In the second method one test MAb was immobilized on a plastic surface through an immunochemical bridge. This MAb was then incubated with 125I-hCG previously complexed with a second MAb. Such a complex could bind to the solid phase MAb only if the two MAbs were not identical. The results obtained with both methods were concordant. With such methods it is possible to identify MAbs with identical epitope specificities immediately after the initial screening of the fusion. These methods do not require subcloning, ascites production, or the purification and iodination of large number of MAbs.