Southern blot analysis of switch regions in 2 patients with “high-grade” MALT lymphoma.

(A) Case No. 6 shows 2 illegitimate switch fragments identified by the 5′Sμ probe and by the 3′Sμ probe on an SphI digest. Two additional illegitimate switch fragments are identified by the 5′ςμ and the 3′ςδ probes on a BglII digest. (B) Case No. 7 presents 1 illegitimate 3′Sμ fragment, 3 5′Sγ fragments (2 of them cohybridize with the 3γ probe), and 1 3′Sα fragment, all on HindIII digest.