Homologous elements hs3a and hs3b in the 3' regulatory region of the murine immunoglobulin heavy chain (Igh) locus are both dispensable for class-switch recombination.

@article{Yan2011HomologousEH,
  title={Homologous elements hs3a and hs3b in the 3' regulatory region of the murine immunoglobulin heavy chain (Igh) locus are both dispensable for class-switch recombination.},
  author={Yi Xiang Yan and Joyce Pieretti and Zhongliang Ju and Shiniu Wei and John R Christin and Fatmata Bah and Barbara K. Birshtein and Laurel Ann Eckhardt},
  journal={The Journal of biological chemistry},
  year={2011},
  volume={286 31},
  pages={
          27123-31
        }
}
Immunoglobulin heavy chain (IgH) genes are formed, tested, and modified to yield diverse, specific, and high affinity antibody responses to antigen. The processes involved must be regulated, however, to avoid unintended damage to chromosomes. The 3' regulatory region of the Igh locus plays a major role in regulating class-switch recombination (CSR), the process by which antibody effector functions are modified during an immune response. Loss of all known enhancer-like elements in this region… CONTINUE READING