Deletion of the immunoglobulin heavy chain 3′ regulatory region super-enhancer affects somatic hypermutation in B1 B cells

Mouse B1 B cells originate in the embryonic liver and are the major B-cell population in the peritoneal and pleural cavities.1–5 By contrast,mouse B2 B cells originate in the bone marrow and are the major B-cell population in the bone marrow,spleen,and blood.B1 and B2 B cells differ not only in their origin and locations,but also in their antigen specificity,cell surface markers,capacities for class-switch recombination(CSR)and somatic hypermutation(SHM).IgH cis-regulatory regions and,particularly,transcriptional super-enhancers are major locus regulators under both normal and pathological conditions.6,7 Important differences have been found regarding the ability of the IgH 3′regulatory region(3′RR)super-enhancer to control the B1 and B2 B-cell fate.