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FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects

In autoimmune diseases, toll-like receptor (TLR)-stimulated pro-inflammatory IL-6-secreting B cells exert pathogenic roles. Similarly, B cell Fc receptor-like 4 (FcRL4) expression amplifies TLR stimulation, and in rheumatoid arthritis patients, FcRL4 expression identifies a pro-inflammatory B cell s...

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Autores principales: Siewe, Basile, Nipper, Allison J., Sohn, Haewon, Stapleton, Jack T., Landay, Alan
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5655023/
https://www.ncbi.nlm.nih.gov/pubmed/29104574
http://dx.doi.org/10.3389/fimmu.2017.01339
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author Siewe, Basile
Nipper, Allison J.
Sohn, Haewon
Stapleton, Jack T.
Landay, Alan
author_facet Siewe, Basile
Nipper, Allison J.
Sohn, Haewon
Stapleton, Jack T.
Landay, Alan
author_sort Siewe, Basile
collection PubMed
description In autoimmune diseases, toll-like receptor (TLR)-stimulated pro-inflammatory IL-6-secreting B cells exert pathogenic roles. Similarly, B cell Fc receptor-like 4 (FcRL4) expression amplifies TLR stimulation, and in rheumatoid arthritis patients, FcRL4 expression identifies a pro-inflammatory B cell subset. B cells from HIV-infected subjects also express heightened levels of FcRL4 and secrete high levels of IL-6: a critical mediator of HIV disease progression. In this study, we sought to determine if FcRL4 identifies a pro-inflammatory B cell subset in HIV-infected subjects and further elucidate the mechanisms underlying FcRL4 amplification of TLR stimulation. We determine that tissue-like memory B cells express the highest endogenous levels of FcRL4 positively correlating with IL-6 expression (p = 0.0022, r = 0.8667), but activated memory B cells exhibit the highest frequency of FcRL4(hi)IL-6(hi) cells. FcRL4(hi) B cells exhibit an activated TLR-signaling pathway identified by elevated phosphorylation levels of: pERK (p = 0.0373), p38 (p = 0.0337), p65 (p = 0.1097), and cJUN (p = 0.0239), concomitant with significantly elevated expression of the TLR-signaling modulator hematopoietic cell kinase (HcK, p = 0.0414). Compared to FcRL4(neg) B cells from healthy controls, TLR9-stimulated FcRL4(pos) B cells express significantly higher levels of lL-6 (p = 0.0179). Further, TLR9-stimulated B cells also upregulate the expression of FcRL4 (p = 0.0415) and HcK (p = 0.0386). In B-cell lines, siRNA-mediated HcK knockdown downmodulates TLR9-induced FcRL4-mediated activation quantified by CD23 upregulation (p = 0.0553). We present data suggesting that, in viremic HIV-infected individuals, FcRL4 expression identifies unique IL-6 producing pro-inflammatory B-cell subsets. Further, TLR stimulation likely modulates FcRL4 expression and FcRL4 expression is associated with Hck, potentially enhancing the activation of TLR-signaling associated transcription factors. Pathogenic B-cells have been identified in other disease settings, and this study represents a novel report describing a pro-inflammatory B cell subset in HIV-infected patients.
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spelling pubmed-56550232017-11-03 FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects Siewe, Basile Nipper, Allison J. Sohn, Haewon Stapleton, Jack T. Landay, Alan Front Immunol Immunology In autoimmune diseases, toll-like receptor (TLR)-stimulated pro-inflammatory IL-6-secreting B cells exert pathogenic roles. Similarly, B cell Fc receptor-like 4 (FcRL4) expression amplifies TLR stimulation, and in rheumatoid arthritis patients, FcRL4 expression identifies a pro-inflammatory B cell subset. B cells from HIV-infected subjects also express heightened levels of FcRL4 and secrete high levels of IL-6: a critical mediator of HIV disease progression. In this study, we sought to determine if FcRL4 identifies a pro-inflammatory B cell subset in HIV-infected subjects and further elucidate the mechanisms underlying FcRL4 amplification of TLR stimulation. We determine that tissue-like memory B cells express the highest endogenous levels of FcRL4 positively correlating with IL-6 expression (p = 0.0022, r = 0.8667), but activated memory B cells exhibit the highest frequency of FcRL4(hi)IL-6(hi) cells. FcRL4(hi) B cells exhibit an activated TLR-signaling pathway identified by elevated phosphorylation levels of: pERK (p = 0.0373), p38 (p = 0.0337), p65 (p = 0.1097), and cJUN (p = 0.0239), concomitant with significantly elevated expression of the TLR-signaling modulator hematopoietic cell kinase (HcK, p = 0.0414). Compared to FcRL4(neg) B cells from healthy controls, TLR9-stimulated FcRL4(pos) B cells express significantly higher levels of lL-6 (p = 0.0179). Further, TLR9-stimulated B cells also upregulate the expression of FcRL4 (p = 0.0415) and HcK (p = 0.0386). In B-cell lines, siRNA-mediated HcK knockdown downmodulates TLR9-induced FcRL4-mediated activation quantified by CD23 upregulation (p = 0.0553). We present data suggesting that, in viremic HIV-infected individuals, FcRL4 expression identifies unique IL-6 producing pro-inflammatory B-cell subsets. Further, TLR stimulation likely modulates FcRL4 expression and FcRL4 expression is associated with Hck, potentially enhancing the activation of TLR-signaling associated transcription factors. Pathogenic B-cells have been identified in other disease settings, and this study represents a novel report describing a pro-inflammatory B cell subset in HIV-infected patients. Frontiers Media S.A. 2017-10-20 /pmc/articles/PMC5655023/ /pubmed/29104574 http://dx.doi.org/10.3389/fimmu.2017.01339 Text en Copyright © 2017 Siewe, Nipper, Sohn, Stapleton and Landay. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Immunology
Siewe, Basile
Nipper, Allison J.
Sohn, Haewon
Stapleton, Jack T.
Landay, Alan
FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects
title FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects
title_full FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects
title_fullStr FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects
title_full_unstemmed FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects
title_short FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects
title_sort fcrl4 expression identifies a pro-inflammatory b cell subset in viremic hiv-infected subjects
topic Immunology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5655023/
https://www.ncbi.nlm.nih.gov/pubmed/29104574
http://dx.doi.org/10.3389/fimmu.2017.01339
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