Ig gene fingerprinting analysis of IgM (μ), IgG (γ), and IgA (α) heavy chain transcripts present in a neoplastic lymph node and a PB sample obtained from patient SEL. A dominant band corresponding to the lymphoma V_H gene rearrangement can be seen in the fingerprint of the μ and γ transcripts from the lymph node. A prominent band of the same size is present in the fingerprint of μ transcripts expressed by PB lymphocytes. Sequencing reactions were used as markers to determine the exact sizes of the bands.