Abstract
Somatic cell mutants with deletions in the immunoglobulin constant region were isolated from an IgG(2b) Ar-binding hybridoma. Rat anti-mouse immunoglobulins were used to identify the sites of the deletions. The mutant monoclonal antibodies differ from the parental molecule in their assembly states and are defective in various immunoglobulin activities, making them potentially more useful reagents.