c-Rel plays a key role in deficient activation of B cells from a non-X-linked hyper IgM patient

Lu KT, Sinquett FL, Dryer RL, Song C, Covey LR
Source: Blood
Publication Date: (2006)
Issue: 108(12): 3769-76
Research Area:
Cancer Research/Cell Biology
Immunotherapy / Hematology
Cells used in publication:
Species: human
Tissue Origin: blood
Nucleofector® I/II/2b
2x10^6 LCL(tet) cells were transfected with 3 µg plasmid DNA or 7.5 nM siRNA using program O-06 for plasmid and U-015 for siRNA
Our previous results demonstrated that B cells from a patient (pt1) with non-X-linked hyper-IgM syndrome (HIGM) possess an atypical CD23(lo) phenotype that is unaffected by CD40-mediated activation. To investigate the molecular mechanism underlying defective CD23 expression in pt1 B cells, we used lymphoblastoid cell lines that express LMP1 under the control of a tetracycline-inducible promoter (LCL(tet)). Our analysis revealed that the CD23(lo) phenotype in the pt1-LCL(tet) cells is a direct consequence of diminished CD23 transcription. We demonstrate a marked decrease in c-Rel-containing complexes that bind to the proximal CD23a/b promoters in pt1-LCL(tet) extracts, resulting from an overall lower expression of c-Rel in pt1-LCL(tet) cells. Analysis of c-Rel mRNA revealed relatively equal amounts in pt1-LCL(tet) and control LCL(tet) cells, indicating that diminished c-Rel protein expression is unrelated to decreased transcription. Finally, a critical role for c-Rel in CD23 regulation was demonstrated by effectively altering c-Rel expression that resulted in the direct modulation of CD23 surface expression. Collectively, these findings demonstrate that low levels of c-Rel are the underlying cause of aberrant CD23 expression in pt1 B cells and are likely to play a critical role in the pathophysiology of this form of HIGM.