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

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• 作者：Peter Szodoray ; MD ; PhD^a ; ^{peter.szodoray@medisin.uio.no" class="auth_mail" title="E-mail the corresponding author} ; Stephanie M. Stanford ; PhD^b ; &Oslash ; yvind Molberg ; MD ; PhD^c ; ^d ; Ludvig A. Munthe ; MD ; PhD^a ; ^d ; Nunzio Bottini ; MD ; PhD^b ; Britt Nakken ; PhD^a
• 关键词：B-cell anergy ; break of tolerance ; T-cell help ; CD45 phosphatase activity ; systemic lupus erythematosus
• 刊名：Journal of Allergy and Clinical Immunology
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：138
• 期：3
• 页码：839-851.e8
• 全文大小：5991 K

文摘

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

absSec_2">Objective

abspara0015">We sought to identify the molecular mechanism of how anergic autoreactive B_ND cells escape functional anergy and whether this process is altered in patients with lupus.

absSec_3">Methods

abspara0020">Isolated peripheral blood naive and B_ND cells were cultured with various stimuli, and their activation status was determined by using an intracellular Ca²⁺ 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.

absSec_4">Results

abspara0025">T-helper signals reversed the state of anergy, allowing B_ND 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 B_ND and naive B cells. Furthermore, we found that B_ND cells obtained from patients with systemic lupus erythematosus exhibited increased CD45 activity and BCR-signaling capacity, thus being less tolerized than B_ND cells from healthy control subjects.

absSec_5">Conclusion

abspara0030">Our findings suggest that CD45 is a key regulator of BCR-signaling thresholds mediated by T-cell help. This raises the possibility that B_ND 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.