B Cell Signature during Inactive Systemic Lupus Is Heterogeneous: Toward a Biological Dissection of Lupus

Jean-Claude Garaud,Doulaye Dembele,Thierry Martin,Julie Ruer-Laventie,Anne-Marie Knapp,Jean-Louis Pasquali,Anne-Sophie Korganow,Pauline Soulas-Sprauel,Jean-Nicolas Schickel,Gilles Blaison

doi:10.1371/journal.pone.0023900

Abstract

Systemic lupus erythematosous (SLE) is an autoimmune disease with an important clinical and biological heterogeneity. B lymphocytes appear central to the development of SLE which is characterized by the production of a large variety of autoantibodies and hypergammaglobulinemia. In mice, immature B cells from spontaneous lupus prone animals are able to produce autoantibodies when transferred into immunodeficient mice, strongly suggesting the existence of intrinsic B cell defects during lupus. In order to approach these defects in humans, we compared the peripheral B cell transcriptomas of quiescent lupus patients to normal B cell transcriptomas. When the statistical analysis is performed on the entire group of patients, the differences between patients and controls appear quite weak with only 14 mRNA genes having a false discovery rate ranging between 11 and 17%, with 6 underexpressed genes (PMEPA1, TLR10, TRAF3IP2, LDOC1L, CD1C and EGR1). However, unforced hierarchical clustering of the microarrays reveals a subgroup of lupus patients distinct from both the controls and the other lupus patients. This subgroup has no detectable clinical or immunological phenotypic peculiarity compared to the other patients, but is characterized by 1/an IL-4 signature and 2/the abnormal expression of a large set of genes with an extremely low false discovery rate, mainly pointing to the biological function of the endoplasmic reticulum, and more precisely to genes implicated in the Unfolded Protein Response, suggesting that B cells entered an incomplete BLIMP1 dependent plasmacytic differentiation which was undetectable by immunophenotyping. Thus, this microarray analysis of B cells during quiescent lupus suggests that, despite a similar lupus phenotype, different biological roads can lead to human lupus.

Highlights

Systemic lupus erythematosous (SLE) is an autoimmune disease which is clinically and biologically characterized by a wide spectrum of signs variable from one patient to another
Expressed genes in lupus B cells compared to normal B cells According to the MIAME recommendations, the data discussed in this publication have been deposited in NCBI’s Gene Expression Omnibus and are accessible through GEO Series accession number GSE30153 as well as the full normalized and annotated results of the RMA analysis of the 2,327 genes with initial p values of less than 0.05 (Table S1)
The B cells transcriptional profiles originating from the 17 lupus patients compared to the 9 normal individuals were analysed using the Significance Analysis of Microarrays (SAM) algorithm and multiple testing correction according to Benjamini et al [14,15]

Summary

Introduction

Systemic lupus erythematosous (SLE) is an autoimmune disease which is clinically and biologically characterized by a wide spectrum of signs variable from one patient to another. Different organs can be affected in groups of patients with SLE, and the immunological hallmark of the disease, the autoantibodies, are diversely expressed with the exception of antinuclear antibodies which are quasi-constant in patients This phenotypic heterogeneity of SLE patients may reflect different genetic contributions (i.e. various combinations of susceptibility genes) and/or different environmental factors which could lead to diverse immunopathological consequences. In an effort to track down putative intrinsic B cell defects during SLE, we analysed the transcriptomas of purifed B cells from inactive patients without immunosuppressive treatment, and compared the SLE B cell gene expression to healthy individual B cell transcriptomas This approach, using purifed B lymphocytes instead of a mixture of peripheral mononuclear cells and non hypothesis driven large scale microarrays, should be able to point out the implication of some biological pathways, and to define such intrinsic B cell defects. A subgroup of patients was clearly distinct from the others and from the controls, with differentially expressed genes mainly implicated in plasmacytic differentiation and confirming at the B cell level the heterogeneity of the pathways leading to lupus

Methods

Results

Conclusion