Biochemical genetics of the mouse IgM system.

Using a mouse hybridoma system, we have developed methods of isolating a variety of mutant cell lines in which immunoglobulin function or synthesis is defective. The analysis of mutants defective in kappa chain synthesis has defined a class of murine transposons. The deletion mutants produce immunoglobulin M (IgM) bearing mu heavy chain fragments and provide information on the requirements of IgM assembly and mu gene expression. We also describe a transfer system for the mu and kappa genes which will be useful in analyzing the structural basis of IgM function.