IL-6 Modulates CD5 Expression in B Cells from Patients with Lupus by Regulating DNA Methylation

Abstract

B lymphocytes from patients with systemic lupus erythematosus (SLE) are characterized by reduced expression levels of membrane CD5. Recent studies from our laboratory have revealed that the level of membrane CD5 is determined by the relative level of two alternative CD5 isoforms; CD5-E1A, which is expressed on the membrane, and CD5-E1B, which is retained in the cytoplasm. Using bisulfite sequencing and methylation-sensitive endonuclease assays we show that the promoter for the alternative CD5-E1B isoform is demethylated in B cells from patients with SLE but not in healthy controls. We go on to show that differential methylation is more pronounced following BCR engagement. As a result of this demethylation, CD5-E1B mRNA is transcribed at the expense of CD5-E1A mRNA transcription. We provide further evidence that production of high IL-6 levels by SLE B cells abrogates the ability of SLE B cells to induce DNA methyl transferase (DNMT1) and then to methylate DNA, an effect that is reversed in the presence of a blocking Ab to the IL-6 receptor. S ystemic lupus erythematosus (SLE)4 is associated with diverse clinical manifestations (1). The main features of autoimmunity in SLE are B cell hyperactivity, spontaneous lymphocyte proliferation, and the production of pathogenic Abs to self-Ags. B cell abnormalities in SLE also include excess cytokine production, autoantigen presentation to T cells and modulation of the function of other immune cells (2). Thus, SLE is generally considered a B cell disease, a theme strengthened by the efficacy of therapies targeting B cells. For example, therapeutic approaches using depleting anti-CD20 has proved to be highly beneficial in treatment of SLE (3). Further, neutralization of cytokines that promote B cell responses such as IL-6, or interruption of cognate T cell and B cell interactions has been successful in early clinical trials (4,5). All this provides the rationale for further investigation of mechanisms of B cell involvement in driving autoimmunity and to develop more selective therapeutic targets.The central role played by B cells in immunity necessitates that its responses are tightly regulated. B cell responses are initiated by signaling through the BCR. Signaling initiated following BCR engagement is regulated by coreceptors and by a network of protein tyrosine kinases and phosphatases. Recent findings suggest that defects in BCR-mediated signaling can result in lupus autoimmunity. For example, there is an association between SLE autoimmunity and mutations in a number of genes that encode B cellspecific signaling molecules including protein tyrosine kinases, non-receptor phosphatase type 22, B cell scaffold protein with ankyrin repeats 1 and the inhibitory IgG Fc␥RIIb (6). In addition to direct evidence for the effect of mutations in signaling molecules on BCR-mediated signaling, the contribution of epigenetic factors has also been proposed (7). The most commonly observed epigenetic abnormality implicated in SLE pathology is altered DNA methylation at the 5-carbon positio...

Increased numbers of CD5+ B lymphocytes with a regulatory phenotype in spondylarthritis

“…A potential regulatory role of CD19ϩCD5ϩ cells in vivo has been suggested in a number of other immune-mediated inflammatory diseases, from studies using different translational approaches. In SLE, peripheral blood B cells display reduced levels of CD5, which could promote the activation and expansion of autoreactive B cells, and the CD5-expressing CD19ϩCD24 high CD38 high Breg cells are functionally impaired (36,48). In kidney graft transplantation, transplant tolerance is associated with a strong B cell signature and an increased number of circulating B cells with an inhibitory phenotype, including CD5 expression (49,50).…”

“…Sixty-one percent were positive for anti-citrullinated protein antibodies and 59% for rheumatoid factor. Blood was also collected from 26 healthy controls who were matched to the SpA cohort by age and sex (62% male and 38% female; median age 40 years [range [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49]). Additionally, we obtained peripheral blood samples from 12 SpA patients before and 12 weeks after initiation of treatment with the TNF blocker adalimumab.…”

Epigenetics in autoimmune disorders: Highlights of the 10th Sjögren's Syndrome Symposium

“…Yves Renaudineau (University of Brest, France) presented evidence detailing the contribution of DNA demethylation defects to the autoreactivity of B cells [22].…”

B cells biology in systemic lupus erythematosus—from bench to bedside

“…Engagement of BCR and production of IL-6 down-regulate membrane CD5 expression through abnormally enhanced demethylation which can influence the balance of the transcripts of two CD5 isoforms (membrane CD5 and cytoplasmic CD5). As a negative regulator of BCR signaling, reduced membrane CD5 leads to activation and expansion of autoreactive B cells in SLE [56].…”

“…CD5 expression on lupus B cells membrane is characteristically reduced [56]. CD5 + B cells are capable of producing IL-10 and possess regulatory potency [37].…”