Generation of antibody diversity subsequent to antigenic stimulation

Experiments are presented in which spleen cells from donor mice, exhibiting a clonally very restricted early antibody response to a small RNA bacteriophage, are transferred at limiting cell dose into irradiated syngeneic recipients. Antibodies produced in such recipients were analyzed with regard to isoelectric points (pI's). Most antibodies in the recipients were found to differ from the donor, but the pI range into which they fall is frequently fairly narrow and related to the pI of the donor. It is suggested that most recipient clones may be derived from a common ancestral precursor cell by somatic mutation in immunoglobulin genes, conceivably subsequent to antigenic stimulation. If such a process should indeed account for the observed diversity, it would imply an unusually high mutation rate.