Immunology Letters 94 (2004) 77–81 The polymorphism of the locus control region lying downstream the human IgH locus is restricted to hs1,2 but not to hs3 and hs4 enhancers Laurence Guglielmi, Véronique Truffinet, Emmanuelle Magnoux, Michel Cogné, Yves Denizot ∗ Laboratoire d’Immunologie, UMR CNRS 6101, Faculté de Médecine, 2 rue Dr. Marcland, 87025 Limoges, France Received 29 January 2004; received in revised form 8 April 2004; accepted 13 April 2004 Available online 6 May 2004 Abstract In human, three transcriptional enhancers called hs1,2, hs3 and hs4 were identified downstream the 3 ′ Ig heavy (IgH) locus. We previously reported by PCR and Southern blotting the existence of various allelic forms for the hs1,2 enhancer, one allele being associated with a higher efficiency of switching to IgA in IgA nephropathy (IgAN) patients. Since it is strongly suggested in the mouse that the whole 3 ′ regulatory region is broadly involved in the regulation of class switch recombination (CSR), we wondered if the reported hs1,2 polymorphism was the sole difference possibly accounting for the varying ability to produce non-IgM antibodies in the human population. In this study, we report the absence of additional polymorphism of the hs3 and hs4 enhancers either by using a PCR method or by Southern blotting. DNA sequence analysis confirmed the existence of an invariant core sequence for human hs3 and hs4 enhancers, featuring multiple nuclear factor potential binding sites. In conclusion, human hs3 and hs4 enhancers are not polymorphic, a result that markedly contrasts with the hs1,2 enhancer for which the generation of multiple alleles in both rodents and humans has likely been favored by its central position within a large palindromic region. © 2004 Elsevier B.V. All rights reserved. Keywords: 3 ′ IgH enhancers; hs1,2; hs3; hs4; Polymorphism; Nuclear factor binding sites In human, a 3 ′ regulatory region lying downstream each  immunoglobulin (Ig) gene has been identified. It includes three enhancer elements called hs1,2, hs3 and hs4 that could act as a locus control region (LCR) [1,2]. Gene reporter assay and knock out studies have suggested a role of this regulatory region in the control of class switch recombina- tion (CSR) and Ig production in mouse [3–5]. The various 3 ′ Ig heavy (IgH) chain enhancers are by themselves weak, but their combinations reveal a strong “co-enhancer” activ- ity [1,2]. Taking advantage of the spontaneous GFP fluo- rescence, we have recently reported in a transgenic mouse model that a GFP-3 ′ LCR transgene yielded an expression from pre-B cells to mature B cells and a stringent repres- sion in non-B cells [6]. In association with the intronic el- ∗ Corresponding author. Tel.: +33-5-55-43-58-96; fax: +33-5-55-43-58-97. E-mail address: yves.denizot@unilim.fr (Y. Denizot). ement E, the GFP-3 ′ LCR transgene yielded an expression from pro-B cells to mature B cells [7]. We have previously reported the existence of a complex polymorphism for the human hs1,2 enhancer for which multiple alleles have been generated through inversions and internal deletions and/or duplication [8]. This polymorphism is of importance since alleles of the 1 hs1,2 enhancer control the level of IgA production in patients and the evolution of IgA nephropa- thy (IgAN) towards renal failure [9,10]. Additional sequence variations of cis-regulatory elements may potentially also be involved in these phenotypic variations, specially if they were affecting the hs3 and hs4 enhancers which were re- cently characterized in the mouse as master control elements of CSR accessibility [5]. In a further attempt to improve our knowledge concerning this 3 ′ LCR, we thus wished to inves- tigate the potential existence of additional polymorphisms affecting the hs3 or hs4 elements by PCR, Southern blot and sequence analysis. 0165-2478/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.imlet.2004.04.003