IgH locus at 14q32.

Top, IgH locus organization showing the localization of the switch probes and of the restriction enzymes (vertical lines) used for the Southern blot assay. Because there is no conventional switch region upstream of Cδ, the 5′ςμ and 3′ςδ probes were used to detect δ rearrangements. Distances between restriction sites in germline configuration are also represented. H = HindIII, B = BglII, S = SphI, LCR = locus control region. Bottom, Enlargement of the intronic enhancer region (Eμ). Numbers above the restriction sites indicate their postions in the GenBank sequence HSIMMDL.