Figure 4.

Southern blot analysis of switch regions in two patients with MM. Genomic DNA from two tumor samples was digested with the indicated restriction enzyme, and Southern blots were analyzed sequentially with various switch probes as described in Fig. 2. The probe is indicated above each lane. (A) Patient 1. (B) Patient 2. For patient 2, DNA was prepared from bone marrow (BM) or blood (BL). Illegitimate switch recombination fragments are indicated by 4 (corresponding to the chromosome involved in the recombination), and ∗ if it has not been cloned. Productive recombination fragments are indicated by a p, and germ-line fragments by a g.