Somatic mutation and the origin of antibody diversity. Clonal variability of the immunoglobulin produced by MOPC 21 cells in culture

Abstract

Abstract A method has been developed for the screening of immunoglobulins produced by large numbers of individual clones of the mouse myeloma (MOPC 21) in tissue culture. Clones grown in agar were incubated in the presence of radioactive amino acids and applied directly onto polyacrylamide plates for isoelectric focusing. A discrete number of well‐defined immunoglobulin bands were then detected by autoradiography. The following variations between different clones were observed: 1. Variation in relative intensity of the different bands. 2. Total absence of immunoglobulin bands. 3. Variation in the position of the bands along the pH gradient. When a mutant clone exhibiting this third type of variation was purified by subcloning, only the mutant pattern was observed. Thus, the cells appear to express only a single allele, although they are known to be aneuploid. We consider the third type of variation to be relevant in the evaluation of the contribution of somatic mutation to the diversity of antibody structure.