The role of B cells and posttranslational modifications in pathogenesis of organ-specific immune diseases is increasingly envisioned but remains poorly understood, particularly in human disorders. In celiac disease, transglutaminase 2–modified (TG2-modified; deamidated) gluten peptides drive disease-specific T cell and B cell responses, and antibodies to deamidated gluten peptides are excellent diagnostic markers. Here, we substantiate by high-throughput sequencing of IGHV genes that antibodies to a disease-specific, deamidated, and immunodominant B cell epitope of gluten (PLQPEQPFP) have biased and stereotyped usage of IGHV3-23 and IGHV3-15 gene segments with modest somatic mutations. X-ray crystal structures of 2 prototype IGHV3-15/IGKV4-1 and IGHV3-23/IGLV4-69 antibodies reveal peptide interaction mainly via germline-encoded residues. In-depth mutational analysis showed restricted selection and substitution patterns at positions involved in antigen binding. While the IGHV3-15/IGKV4-1 antibody interacts with Glu5 and Gln6, the IGHV3-23/IGLV4-69 antibody interacts with Gln3, Pro4, Pro7, and Phe8 — residues involved in substrate recognition by TG2. Hence, both antibodies, despite different interaction with the epitope, recognize signatures of TG2 processing that facilitates B cell presentation of deamidated gluten peptides to T cells, thereby providing a molecular framework for the generation of these clinically important antibodies. The study provides essential insight into the pathogenic mechanism of celiac disease.
Omri Snir, Xi Chen, Moriah Gidoni, M. Fleur du Pré, Yuguang Zhao, Øyvind Steinsbø, Knut E.A. Lundin, Gur Yaari, Ludvig M. Sollid
The pathogenesis of primary Sjogren’s syndrome (SS), an autoimmune disease that targets the mucosa of exocrine tissues, is poorly understood. Although several mouse models have been developed that display features of SS, most of these are within the larger context of a lupus-like presentation. Immunity-related GTPase family M protein 1 (Irgm1) is an interferon-inducible cytoplasmic GTPase that is reported to regulate autophagy and mitochondrial homeostasis. Here, we report that naive Irgm1–/– mice display lymphocytic infiltration of multiple mucosal tissues including the lung in a manner reminiscent of SS, together with IgA class–predominant autoantibodies including anti-Ro and anti-La. This phenotype persists in the germ-free state, but is abolished by deletion of Irgm3. Irgm1–/– mice have increased local production in the lung of TECP15-idiotype IgA, a natural antibody with dual reactivity against host and pneumococcal phosphorylcholine. Associated with this, Irgm1–/– mice display enhanced opsonization and clearance of Streptococcus pneumoniae from the lung and increased survival from pneumococcal pneumonia. Taken together, our results identify Irgm1 as a master regulator of mucosal immunity that dually modulates evolutionarily conserved self- and other-directed immune responses at the interface of host with environment.
Kathleen M. Azzam, Jennifer H. Madenspacher, Derek W. Cain, Lihua Lai, Kymberly M. Gowdy, Prashant Rai, Kyathanahalli Janardhan, Natasha Clayton, Willie Cunningham, Heather Jensen, Preeyam S. Patel, John F. Kearney, Gregory A. Taylor, Michael B. Fessler
The maintenance of peripheral naive T lymphocytes in humans is dependent on their homeostatic division, not continuing emigration from the thymus, which undergoes involution with age. However, postthymic maintenance of naive T cells is still poorly understood. Previously we reported that recent thymic emigrants (RTEs) are contained in CD31+CD25− naive T cells as defined by their levels of signal joint T cell receptor rearrangement excision circles (sjTRECs). Here, by differential gene expression analysis followed by protein expression and functional studies, we define that the naive T cells having divided the least since thymic emigration express complement receptors (CR1 and CR2) known to bind complement C3b- and C3d-decorated microbial products and, following activation, produce IL-8 (CXCL8), a major chemoattractant for neutrophils in bacterial defense. We also observed an IL-8–producing memory T cell subpopulation coexpressing CR1 and CR2 and with a gene expression signature resembling that of RTEs. The functions of CR1 and CR2 on T cells remain to be determined, but we note that CR2 is the receptor for Epstein-Barr virus, which is a cause of T cell lymphomas and a candidate environmental factor in autoimmune disease.
Marcin L. Pekalski, Arcadio Rubio García, Ricardo C. Ferreira, Daniel B. Rainbow, Deborah J. Smyth, Meghavi Mashar, Jane Brady, Natalia Savinykh, Xaquin Castro Dopico, Sumiyya Mahmood, Simon Duley, Helen E. Stevens, Neil M. Walker, Antony J. Cutler, Frank Waldron-Lynch, David B. Dunger, Claire Shannon-Lowe, Alasdair J. Coles, Joanne L. Jones, Chris Wallace, John A. Todd, Linda S. Wicker
The chemokine receptor CCR6 marks subsets of T cells and innate lymphoid cells that produce IL-17 and IL-22, and as such may play a role in the recruitment of these cells to certain inflammatory sites. However, the precise role of CCR6 has been controversial, in part because no effective monoclonal antibody (mAb) inhibitors against this receptor exist for use in mouse models of inflammation. We circumvented this problem using transgenic mice expressing human CCR6 (hCCR6) under control of its native promoter (hCCR6-Tg/mCCR6–/–). We also developed a fully humanized mAb against hCCR6 with antagonistic activity. The expression pattern of hCCR6 in hCCR6-Tg/mCCR6–/– mice was consistent with the pattern observed in humans. In mouse models of experimental autoimmune encephalomyelitis (EAE) and psoriasis, treatment with anti-hCCR6 mAb was remarkably effective in both preventive and therapeutic regimens. For instance, in the imiquimod model of psoriasis, anti-CCR6 completely abolished all signs of inflammation. Moreover, anti-hCCR6 attenuated clinical symptoms of myelin oligodendrocyte glycoprotein–induced (MOG-induced) EAE and reduced infiltration of inflammatory cells in the central nervous system. CCR6 plays a critical role in Th17 type inflammatory reactions, and CCR6 inhibition may offer an alternative approach for the treatment of these lesions.
Remy Robert, Caroline Ang, Guizhi Sun, Laurent Juglair, Ee X. Lim, Linda J. Mason, Natalie L. Payne, Claude C.A. Bernard, Charles R. Mackay
GPCR expression was intensively studied in bulk cDNA of leukocyte populations, but limited data are available with respect to expression in individual cells. Here, we show a microfluidic-based single-cell GPCR expression analysis in primary T cells, myeloid cells, and endothelial cells under naive conditions and during experimental autoimmune encephalomyelitis, the mouse model of multiple sclerosis. We found that neuroinflammation induces characteristic changes in GPCR heterogeneity and patterning, and we identify various functionally relevant subgroups with specific GPCR profiles among spinal cord–infiltrating CD4 T cells, macrophages, microglia, or endothelial cells. Using GPCRs CXCR4, S1P1, and LPHN2 as examples, we show how this information can be used to develop new strategies for the functional modulation of Th17 cells and activated endothelial cells. Taken together, single-cell GPCR expression analysis identifies functionally relevant subpopulations with specific GPCR repertoires and provides a basis for the development of new therapeutic strategies in immune disorders.
Denise Tischner, Myriam Grimm, Harmandeep Kaur, Daniel Staudenraus, Jorge Carvalho, Mario Looso, Stefan Günther, Florian Wanke, Sonja Moos, Nelly Siller, Johanna Breuer, Nicholas Schwab, Frauke Zipp, Ari Waisman, Florian C. Kurschus, Stefan Offermanns, Nina Wettschureck
Today, it is known that autoimmune diseases start a long time before clinical symptoms appear. Anti-citrullinated protein antibodies (ACPAs) appear many years before the clinical onset of rheumatoid arthritis (RA). However, it is still unclear if and how ACPAs are arthritogenic. To better understand the molecular basis of pathogenicity of ACPAs, we investigated autoantibodies reactive against the C1 epitope of collagen type II (CII) and its citrullinated variants. We found that these antibodies are commonly occurring in RA. A mAb (ACC1) against citrullinated C1 was found to cross-react with several noncitrullinated epitopes on native CII, causing proteoglycan depletion of cartilage and severe arthritis in mice. Structural studies by X-ray crystallography showed that such recognition is governed by a shared structural motif “RG-TG” within all the epitopes, including electrostatic potential-controlled citrulline specificity. Overall, we have demonstrated a molecular mechanism that explains how ACPAs trigger arthritis.
Changrong Ge, Dongmei Tong, Bibo Liang, Erik Lönnblom, Nadine Schneider, Cecilia Hagert, Johan Viljanen, Burcu Ayoglu, Roma Stawikowska, Peter Nilsson, Gregg B. Fields, Thomas Skogh, Alf Kastbom, Jan Kihlberg, Harald Burkhardt, Doreen Dobritzsch, Rikard Holmdahl
Though recent reports suggest that neutrophil extracellular traps (NETs) are a source of antigenic nucleic acids in systemic lupus erythematosus (SLE), we recently showed that inhibition of NETs by targeting the NADPH oxidase complex via cytochrome b-245, β polypeptide (
Rachael A. Gordon, Jan M. Herter, Florencia Rosetti, Allison M. Campbell, Hiroshi Nishi, Michael Kashgarian, Sheldon I. Bastacky, Anthony Marinov, Kevin M. Nickerson, Tanya N. Mayadas, Mark J. Shlomchik
Many effector mechanisms of neutrophils have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). Neutrophil extracellular traps (NETs) have been assigned a particularly detrimental role. Here we investigated the functional impact of neutrophils and NETs on a mouse model of lupus triggered by intraperitoneal injection of the cell death–inducing alkane pristane. Pristane-induced lupus (PIL) was aggravated in 2 mouse strains with impaired induction of NET formation, i.e., NOX2-deficient (
Deborah Kienhöfer, Jonas Hahn, Julia Stoof, Janka Zsófia Csepregi, Christiane Reinwald, Vilma Urbonaviciute, Caroline Johnsson, Christian Maueröder, Malgorzata J. Podolska, Mona H. Biermann, Moritz Leppkes, Thomas Harrer, Malin Hultqvist, Peter Olofsson, Luis E. Munoz, Attila Mocsai, Martin Herrmann, Georg Schett, Rikard Holmdahl, Markus H. Hoffmann
Pemphigus vulgaris (PV) is an epithelial blistering disease caused by autoantibodies to the desmosomal cadherin desmoglein 3 (DSG3). Glucocorticoids improve disease within days by increasing DSG3 gene transcription, although the mechanism for this observation remains unknown. Here, we show that DSG3 transcription in keratinocytes is regulated by Stat3. Treatment of primary human keratinocytes (PHKs) with hydrocortisone or rapamycin, but not the p38 MAPK inhibitor SB202190, significantly increases DSG3 mRNA and protein expression and correspondingly reduces phospho-S727 Stat3. Stat3 inhibition or shRNA-knockdown also significantly increases DSG3 mRNA and protein levels. Hydrocortisone- or rapamycin-treated PHKs demonstrate increased number and length of desmosomes by electron microscopy and are resistant to PV IgG–induced loss of cell adhesion, whereas constitutive activation of Stat3 in PHKs abrogates DSG3 upregulation and inhibits hydrocortisone and rapamycin’s therapeutic effects. Topical hydrocortisone, rapamycin, or Stat3 inhibitor XVIII prevents autoantibody-induced blistering in the PV passive transfer mouse model, correlating with increased epidermal DSG3 expression and decreased phospho-S727 Stat3. Our data indicate that glucocorticoids and rapamycin upregulate DSG3 transcription through inhibition of Stat3. These studies explain how glucocorticoids rapidly improve pemphigus and may also offer novel insights into the physiologic and pathophysiologic regulation of desmosomal cadherin expression in normal epidermis and epithelial carcinomas.
Xuming Mao, Michael Jeffrey T. Cho, Christoph T. Ellebrecht, Eric M. Mukherjee, Aimee S. Payne
Multiple sclerosis (MS) is an inflammatory CNS demyelinating disease in which remyelination largely fails. Transmembrane TNF (tmTNF) and TNF receptor 2 are important for remyelination in experimental MS models, but it is unknown whether soluble TNF (solTNF), a major proinflammatory factor, is involved in regeneration processes. Here, we investigated the specific contribution of solTNF to demyelination and remyelination in the cuprizone model. Treatment with XPro1595, a selective inhibitor of solTNF that crosses the intact blood-brain barrier (BBB), in cuprizone-fed mice did not prevent toxin-induced oligodendrocyte loss and demyelination, but it permitted profound early remyelination due to improved phagocytosis of myelin debris by CNS macrophages and prevented disease-associated decline in motor performance. The beneficial effects of XPro1595 were absent in TNF-deficient mice and replicated in tmTNF-knockin mice, showing that tmTNF is sufficient for the maintenance of myelin and neuroprotection. These findings demonstrate that solTNF inhibits remyelination and repair in a cuprizone demyelination model and suggest that local production of solTNF in the CNS might be one reason why remyelination fails in MS. These findings also suggest that disinhibition of remyelination by selective inhibitors of solTNF that cross the BBB might represent a promising approach for treatment in progressive MS.
Maria Karamita, Christopher Barnum, Wiebke Möbius, Malú G. Tansey, David E. Szymkowski, Hans Lassmann, Lesley Probert
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