Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Activation of Interferon and Ubiquitin Pathways in Lupus Memory B Cells
Olferiev, Mikhail, Crow, Mary K.
Memory B cells from patients with systemic lupus erythematosus (SLE) represent an important cell population that is associated with disease activity and contributes to production of pathogenic IgG autoantibodies. To gain further insight into the mechanisms of altered B cell function in SLE, we investigated the molecular pathways activated in SLE and healthy donor (HD) memory B cells using gene expression profiling.
Seven adult female patients with established SLE (100% ANA positive; SLEDAI score >4 and <12) and seven HD participated in the study. B cells were first enriched from peripheral blood and the CD19+CD27+ memory B cell subset separated from naïve B cells (CD19+CD27-) on a FACS Vantage cell sorter. Microarray analysis of mRNA derived from SLE and HD samples was performed using the Affymetrix Human U133 2.0 chip. Gene expression analysis was carried out using GeneSpring GX 10 software. Samples were per-chip normalized and transformed to the baseline median level. Student T-test was performed to determine differentially expressed genes between the two groups.
1183 genes were found to be differentially expressed between SLE and HD CD19+CD27+ cells [Fold Change (FC) >1.5, p<0.05]. Among those, 30 genes showed strong significance for differential expression (FC>1.5, p<0.01). Unsupervised cluster analysis clearly discriminated patients with SLE from HD. Functional analysis revealed enrichment of genes related to Ig synthesis, interferon (IFN) signature, B cell signaling and the ubiquitin pathway. Genes with likely relevance to autoimmunity were significantly overexpressed in SLE memory B cells, including AICDA and GCET2 (p<0.01). Increased expression of TLR7 and IRF7 and of type I IFN-inducible genes (STAT1, IFI27, IFIT1, IFITM1, OAS2/3/L) identified lupus memory B cells as active participants in type I IFN production and response, and the expression of CD72 and CD22 inhibitory receptors was low. Expression of several ubiquitin conjugating enzymes and ubiquitin ligases was increased in memory B cells from SLE patients, including TRIM25, an E3 ubiquitin ligase responsible for ubiquitylation of RIGI, a mediator of TLR-independent type I IFN production.
mRNA expression was dysregulated in SLE memory B cells, consistent with an important contribution of those cells to the immunoregulatory disturbances that result in autoimmunity and disease. In addition to patterns characteristic of active Ig synthesis and an IFN signature, we identified activation of the ubiquitin machinery, including a participant in TLR-independent IFN production, in lupus memory B cells, pointing to an additional pathway that may be important in lupus pathogenesis.
To cite this abstract, please use the following information:
Olferiev, Mikhail, Crow, Mary K.; Activation of Interferon and Ubiquitin Pathways in Lupus Memory B Cells [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1989