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J Allergy Clin Immunol. 2016 Sep;138(3):839-851.e8. doi: 10.1016/j.jaci.2016.01.035. Epub 2016 Apr 4.

T-helper signals restore B-cell receptor signaling in autoreactive anergic B cells by upregulating CD45 phosphatase activity.

Author information

1
Centre for Immune Regulation, Department of Immunology, University of Oslo and Oslo University Hospital-Rikshospitalet, Oslo, Norway. Electronic address: peter.szodoray@medisin.uio.no.
2
Division of Cellular Biology, La Jolla Institute for Allergy and Immunology, La Jolla, Calif.
3
Department of Rheumatology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
4
Centre for Immune Regulation, Department of Immunology, University of Oslo and Oslo University Hospital-Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
5
Centre for Immune Regulation, Department of Immunology, University of Oslo and Oslo University Hospital-Rikshospitalet, Oslo, Norway.

Abstract

BACKGROUND:

We recently identified a human B-cell population that is naturally autoreactive and tolerized by functional anergy (BND cells).

OBJECTIVE:

We sought to identify the molecular mechanism of how anergic autoreactive BND cells escape functional anergy and whether this process is altered in patients with lupus.

METHODS:

Isolated peripheral blood naive and BND cells were cultured with various stimuli, and their activation status was determined by using an intracellular Ca(2+) mobilization assay. Lyn kinase and Syk activities were assessed by using phospho-flow analysis. CD45 phosphatase activity was determined by using a novel flow-based assay, which takes advantage of the fluorogenic properties of phosphorylated coumaryl amino propionic acid, an analog of phosphotyrosine, which can be incorporated into peptides. Real-time quantitative PCR was used to quantitate LYN, SYK, and CD45 mRNA.

RESULTS:

T-helper signals reversed the state of anergy, allowing BND cells to fully respond to antigenic stimulation by restoring signaling through the B-cell receptor (BCR). The mechanism was dependent on increased activity of the tyrosine phosphatase CD45 and CD45-dependent activation of Lyn and Syk. CD45 phosphatase activity was increased by T-cell help both in BND and naive B cells. Furthermore, we found that BND cells obtained from patients with systemic lupus erythematosus exhibited increased CD45 activity and BCR-signaling capacity, thus being less tolerized than BND cells from healthy control subjects.

CONCLUSION:

Our findings suggest that CD45 is a key regulator of BCR-signaling thresholds mediated by T-cell help. This raises the possibility that BND cells could represent precursors of autoantibody-secreting plasma cells and suggests a role for these autoreactive B cells in contributing to autoimmunity if not properly controlled.

KEYWORDS:

B-cell anergy; CD45 phosphatase activity; T-cell help; break of tolerance; systemic lupus erythematosus

PMID:
27056269
DOI:
10.1016/j.jaci.2016.01.035
[Indexed for MEDLINE]

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