Allele-specific Ig gene fingerprinting of IgM-expressing B cells. A schematic representation of the procedure is shown at the top of the figure. The positions of the PCR primers (hFW1 and hM3) and the primers used for labeling the PCR products (hFW3 and 51p1F) are indicated. The autoradiograms show the analysis of peripheral blood lymphocytes from five normal controls (NC1-5) and eight cases with HCV-associated immunocytoma (a BM sample from MEL was also analyzed). The locations of the bands corresponding to 51p1 transcripts and all V_H transcripts are indicated. Expanded 51p1-expressing B-cell clones can clearly be seen in cases LC1, LC6, LC7, and MEL.