Comparison of the heavy chain mutational status in IGHV3-21 expressing IGKV or IGLV genes. The lines indicate the mean percent of IGHV homology in the UM IGKV or IGLV (mean percentage IGHV homology, 99.7% and 98%, respectively) and in the M IGKV or IGLV (mean percentage IGHV homology, 94.8% and 95.3%, respectively).