The Expanded IgD- CD27- CD11c+ B Cell Subpopulation of Systemic Lupus Erythematosus Patients Is Not Anergic, as Measured by Proximal B Cell Receptor-Associated Signaling Open Access

Patel, Aakash Vijay (2015)

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Systemic Lupus Erythematosus (SLE) is a humoral and cell-mediated autoimmune disorder that leads to chronic inflammation of affected tissues such as the joints, skin, kidneys, lungs, heart, brain, and blood vessels. Over-activity of autoreactive B cells is believed to be central to the pathogenesis of SLE. Studies have elucidated an overrepresented subpopulation of potentially autoreactive IgD- CD27- (double negative, DN) B cells in SLE patients. Further, unpublished studies have revealed that these B cells present a unique gene expression phenotype that would promote anergy; for example, they express large amounts of CD11c. Since previous studies have reported the presence of altered intracellular signaling in specific expanded B cell subpopulations from patients with autoimmune diseases such as SLE and RA, this study aims to examine the phosphorylation of B cell linker protein (BLNK), an upstream, activating proximal B cell receptor (BCR)-associated signaling protein specific to B cells, in the expanded DN CD11c+ B cell subpopulation from SLE patients. Peripheral Blood Mononuclear Cells were isolated from 17 SLE patients and one healthy control donor and either stimulated with anti-human IgG or IgM or unstimulated by the addition of just PBS. Cells were paraformaldehyde fixed, methanol permeabilized, and stained with a panel of antibodies to measure phosphorylation of BLNK (Y84) in the various B cell subpopulations using phosphospecific flow cytometry. Our findings show that total DN IgA- B cells induced phosphorylation of BLNK (Y84), although this was statistically lower than in IgD-, CD27+, IgA- B cells. Further, there was no statistically significant difference in proximal BCR-associated signaling between the DN CD11c+ and DN CD11c- B cell subpopulations. Taken together, my data suggest these potentially autoreactive, expanded DN B cells in SLE patients failed to become anergic despite their expression of proteins that would promote anergy; they still induced proximal BCR-associated signaling following stimulation. This failure of potentially autoreactive B cells to become anergic could be due to ineffective anergy-promoting mechanisms and is a characteristic of many autoimmune disorders. Consequently, B cell signaling pathways serve as a major target for future treatments.

Table of Contents

Table of Figures i

Introduction 1

Materials and Methods 6

Results 9

Discussion 25

Conclusion 29

Disclosures 30

References 30

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