Anti-C1q autoantibodies are present in sera of patients with several autoimmune diseases, including systemic lupus erythematosus (SLE). Strikingly, in SLE the presence of anti-C1q is associated with the occurrence of nephritis. We have generated mouse anti–mouse C1q mAb’s and used murine models to investigate whether anti-C1q autoantibodies actually contribute to renal pathology in glomerular immune complex disease. Administration of anti-C1q mAb JL-1, which recognizes the collagen-like region of C1q, resulted in glomerular deposition of C1q and anti-C1q autoantibodies and mild granulocyte influx, but no overt renal damage. However, combination of JL-1 with a subnephritogenic dose of C1q-fixing anti–glomerular basement membrane (anti-GBM) antibodies enhanced renal damage characterized by persistently increased levels of infiltrating granulocytes, major histological changes, and increased albuminuria. This was not observed when a non–C1q-fixing anti-GBM preparation was used. Experiments with different knockout mice showed that renal damage was dependent not only on glomerular C1q and complement activation but also on Fcγ receptors. In conclusion, anti-C1q autoantibodies deposit in glomeruli together with C1q but induce overt renal disease only in the context of glomerular immune complex disease. This provides an explanation why anti-C1q antibodies are especially pathogenic in patients with SLE.
Leendert A. Trouw, Tom W.L. Groeneveld, Marc A. Seelen, Jacques M.G.J. Duijs, Ingeborg M. Bajema, Frans A. Prins, Uday Kishore, David J. Salant, J. Sjef Verbeek, Cees van Kooten, Mohamed R. Daha
Cytokines play key roles in spontaneous CD4+ T cell–mediated chronic autoimmune arthritis in SKG mice, a new model of rheumatoid arthritis. Genetic deficiency in IL-6 completely suppressed the development of arthritis in SKG mice, irrespective of the persistence of circulating rheumatoid factor. Either IL-1 or TNF-α deficiency retarded the onset of arthritis and substantially reduced its incidence and severity. IL-10 deficiency, on the other hand, exacerbated disease, whereas IL-4 or IFN-γ deficiency did not alter the disease course. Synovial fluid of arthritic SKG mice contained high amounts of IL-6, TNF-α, and IL-1, in accord with active transcription of these cytokine genes in the afflicted joints. Notably, immunohistochemistry revealed that distinct subsets of synovial cells produced different cytokines in the inflamed synovium: the superficial synovial lining cells mainly produced IL-1 and TNF-α, whereas scattered subsynovial cells produced IL-6. Thus, IL-6, IL-1, TNF-α, and IL-10 play distinct roles in the development of SKG arthritis; arthritogenic CD4+ T cells are not required to skew to either Th1 or Th2; and the appearance of rheumatoid factor is independent of joint inflammation. The results also indicate that targeting not only each cytokine but also each cell population secreting distinct cytokines could be an effective treatment of rheumatoid arthritis.
Hiroshi Hata, Noriko Sakaguchi, Hiroyuki Yoshitomi, Yoichiroh Iwakura, Kenji Sekikawa, Yoshiaki Azuma, Chieko Kanai, Eiko Moriizumi, Takashi Nomura, Takashi Nakamura, Shimon Sakaguchi
SAMP1/YitFc mice develop discontinuous, transmural inflammatory lesions in the terminal ileum, similar to what is found in human Crohn disease. Compared with the mesenteric lymph nodes (MLNs) of AKR control mice, SAMP1/YitFc MLNs contain a 4.3-fold expansion in total B cell number and a 2.5-fold increased percentage of CD4+ T cells expressing the αEβ7 integrin. Although αEβ7+CD4+ T cells possess a regulatory phenotype (CD25+, L-selectinlo, and CD45RBlo), express IL-10, and suppress effector T cell proliferation in vitro, they cannot prevent ileitis development in SCID mice adoptively transferred with effector CD4+ T cells, although the CD4+CD25+ subset, which overlaps with the αEβ7+CD4+ subset, prevents colitis. The αEβ7+CD4+ T cells express high levels of ICOS, a costimulatory molecule that augments B cell function, suggesting their involvement in the increase in B cells, IgA+ cells, and soluble IgA found within the MLNs and ileum of SAMP1/YitFc mice. MLN B cell numbers correlate with ileitis severity in SAMP1/YitFc mice, and cotransfer of SAMP1/YitFc MLN B cells along with CD4+ T cells increases ileitis severity in SCID mice compared with transfer of CD4+ T cells alone. SAMP1/YitFc B cells prevent αEβ7+CD4+ T cells from suppressing effector T cell proliferation. We conclude that SAMP1/YitFc MLN B cells contribute to the development of SAMP1/YitFc ileitis.
Timothy S. Olson, Giorgos Bamias, Makoto Naganuma, Jesús Rivera-Nieves, Tracy L. Burcin, William Ross, Margaret A. Morris, Theresa T. Pizarro, Peter B. Ernst, Fabio Cominelli, Klaus Ley
The molecular pathogenesis of focal/diffuse proliferative lupus glomerulonephritis was studied by cDNA microarray analysis of gene expression in glomeruli from clinical biopsies. Transcriptional phenotyping of glomeruli isolated by laser-capture microscopy revealed considerable kidney-to-kidney heterogeneity in increased transcript expression, resulting in four main gene clusters that identified the presence of B cells, several myelomonocytic lineages, fibroblast and epithelial cell proliferation, matrix alterations, and expression of type I IFN–inducible genes. Glomerulus-to-glomerulus variation within a kidney was less marked. The myeloid lineage transcripts, characteristic of those found in isolated activated macrophages and myeloid dendritic cells, were widely distributed in all biopsy samples. One major subgroup of the samples expressed fibrosis-related genes that correlated with pathological evidence of glomerulosclerosis; however, decreased expression of TGF-β1 argued against its role in lupus renal fibrosis. Expression of type I IFN–inducible transcripts by a second subset of samples was associated with reduced expression of fibrosis-related genes and milder pathological features. This pattern of gene expression resembled that exhibited by activated NK cells. A large gene cluster with decreased expression found in all samples included ion channels and transcription factors, indicating a loss-of-function response to the glomerular injury.
Karin S. Peterson, Jing-Feng Huang, Jessica Zhu, Vivette D’Agati, Xuejun Liu, Nancy Miller, Mark G. Erlander, Michael R. Jackson, Robert J. Winchester
Today, dilated cardiomyopathy (DCM) represents the main cause of severe heart failure and disability in younger adults and thus is a challenge for public health. About 30% of DCM cases are genetic in origin; however, the large majority of cases are sporadic, and a viral or immune pathogenesis is suspected. Following the established postulates for pathogenesis of autoimmune diseases, here we provide direct evidence that an autoimmune attack directed against the cardiac β1-adrenergic receptor may play a causal role in DCM. First, we immunized inbred rats against the second extracellular β1-receptor loop (β1-ECII; 100% sequence identity between human and rat) every month. All these rats developed first, receptor-stimulating anti–β1-ECII Ab’s and then, after 9 months, progressive severe left ventricular dilatation and dysfunction. Second, we transferred sera from anti–β1-ECII–positive and Ab-negative animals every month to healthy rats of the same strain. Strikingly, all anti–β1-ECII–transferred rats also developed a similar cardiomyopathic phenotype within a similar time frame, underlining the pathogenic potential of these receptor Ab’s. As a consequence, β1-adrenergic receptor–targeted autoimmune DCM should now be categorized with other known receptor Ab-mediated autoimmune diseases, such as Graves disease or myasthenia gravis. Although carried out in an experimental animal model, our findings should further encourage the development of therapeutic strategies that combat harmful anti–β1-ECII in receptor Ab–positive DCM patients.
Roland Jahns, Valérie Boivin, Lutz Hein, Sven Triebel, Christiane E. Angermann, Georg Ertl, Martin J. Lohse
The MHC class I family–like Fc receptor, FcRn, is normally responsible for extending the life span of serum IgG Ab’s, but whether this molecule contributes to autoimmune pathogenesis remains speculative. To determine directly whether this function contributes to humoral autoimmune disease, we examined whether a deficiency in the FcRn heavy chain influences autoimmune arthritis in the K/BxN mouse model. FcRn deficiency conferred either partial or complete protection in the arthritogenic serum transfer and the more aggressive genetically determined K/BxN autoimmune arthritis models. The protective effects of an FcRn deficiency could be overridden with excessive amounts of pathogenic IgG Ab’s. The therapeutic saturation of FcRn by high-dose intravenous IgG (IVIg) also ameliorated arthritis, directly implicating FcRn blockade as a significant mechanism of IVIg’s anti-inflammatory action. The results suggest that FcRn is a potential therapeutic target that links the initiation and effector phases of humoral autoimmune disease.
Shreeram Akilesh, Stefka Petkova, Thomas J. Sproule, Daniel J. Shaffer, Gregory J. Christianson, Derry Roopenian
Systemic lupus erythematosus (SLE) is characterized by abnormalities in T lymphocyte receptor–mediated signal transduction pathways. Our previous studies have established that lymphocyte-specific protein tyrosine kinase (LCK) is reduced in T lymphocytes from patients with SLE and that this reduction is associated with disease activity and parallels an increase in LCK ubiquitination independent of T cell activation. This study investigated the expression of molecules that regulate LCK homeostasis, such as CD45, C-terminal Src kinase (CSK), and c-Cbl, in lipid raft domains from SLE T cells and investigated the localization of these proteins during T cell receptor (TCR) triggering. Our results indicate that the expression of raft-associated ganglioside, GM1, is increased in T cells from SLE patients and LCK may be differentially regulated due to an alteration in the association of CD45 with lipid raft domains. CD45 tyrosine phosphatase, which regulates LCK activity, was differentially expressed and its localization into lipid rafts was increased in T cells from patients with SLE. Furthermore, T cells allowed to “rest” in vitro showed a reversal of the changes in LCK, CD45, and GM1 expression. The results also revealed that alterations in the level of GM1 expression and lipid raft occupancy cannot be induced by serum factors from patients with SLE but indicated that cell-cell contact, activating aberrant proximal signaling pathways, may be important in influencing abnormalities in T cell signaling and, therefore, function in patients with SLE.
Elizabeth C. Jury, Panagiotis S. Kabouridis, Fabian Flores-Borja, Rizgar A. Mageed, David A. Isenberg
Autoimmune sensorineural hearing loss (ASNHL) is characterized typically by bilateral, rapidly progressive hearing loss that responds therapeutically to corticosteroid treatment. Despite its name, data implicating autoimmunity in the etiopathogenesis of ASNHL have been limited, and targeted self-antigens have not been identified. In the current study we show that the inner ear–specific proteins cochlin and β-tectorin are capable of targeting experimental autoimmune hearing loss (EAHL) in mice. Five weeks after immunization of SWXJ mice with either Coch 131–150 or β-tectorin 71–90, auditory brainstem responses (ABR) showed significant hearing loss at all frequencies tested. Flow cytometry analysis showed that each peptide selectively activated CD4+ T cells with a proinflammatory Th1-like phenotype. T cell mediation of EAHL was determined by showing significantly increased ABR thresholds 6 weeks after adoptive transfer of peptide-activated CD4+ T cells into naive SWXJ recipients. Immunocytochemical analysis showed that leukocytic infiltration of inner ear tissues coincided with onset of hearing loss. Our study provides a contemporary mouse model for clarifying our understanding of ASNHL and facilitating the development of novel effective treatments for this clinical entity. Moreover, our data provide experimental confirmation that ASNHL may be a T cell–mediated organ-specific autoimmune disorder of the inner ear.
C. Arturo Solares, Andrea E. Edling, Justin M. Johnson, Moo-Jin Baek, Keiko Hirose, Gordon B. Hughes, Vincent K. Tuohy
We describe the generation of mice that express a transgenic T cell receptor (TCR) (5B6) specific for the encephalitogenic myelin proteolipid protein (PLP) peptide 139–151, on the experimental autoimmune encephalomyelitis–resistant (EAE-resistant) B10.S background. Despite harboring a high frequency of self-reactive T cells, 5B6 transgenic mice on the B10.S background rarely develop spontaneous EAE, which is in striking contrast to 5B6 transgenic mice on the EAE-susceptible SJL background. The relative resistance to spontaneous EAE in transgenic B10.S mice is not due to deletion or anergy of T cells, but appears to be controlled by APCs. Analysis of APCs revealed a lower activation state and a lower T cell–activating capacity for APCs from B10.S mice than for those from EAE-susceptible SJL mice. When APCs in 5B6 transgenic B10.S mice were activated, for example, via TLR9 or TLR4, T cell tolerance was broken, resulting in EAE. Our findings demonstrate that activation of APCs via innate immune receptors can break self tolerance and trigger the development of autoimmunity even in a genetically resistant strain. These findings suggest that the development of autoimmune diseases such as multiple sclerosis is determined at least partly by the endogenous activation state of APCs.
Hanspeter Waldner, Mary Collins, Vijay K. Kuchroo
Whether and how T cells contribute to the pathogenesis of immunoglobulin A nephropathy (IgAN) has not been well defined. Here, we explore a murine model that spontaneously develops T cell–mediated intestinal inflammation accompanied by pathological features similar to those of human IgAN. Intestinal inflammation mediated by LIGHT, a ligand for lymphotoxin β receptor (LTβR), not only stimulates IgA overproduction in the gut but also results in defective IgA transportation into the gut lumen, causing a dramatic increase in serum polymeric IgA. Engagement of LTβR by LIGHT is essential for both intestinal inflammation and hyperserum IgA syndrome in our LIGHT transgenic model. Impressively, the majority of patients with inflammatory bowel disease showed increased IgA-producing cells in the gut, elevated serum IgA levels, and severe hematuria, a hallmark of IgAN. These observations indicate the critical contributions of dysregulated LIGHT expression and intestinal inflammation to the pathogenesis of IgAN.
Jing Wang, Robert A. Anders, Qiang Wu, Dacheng Peng, Judy H. Cho, Yonglian Sun, Reda Karaliukas, Hyung-Sik Kang, Jerrold R. Turner, Yang-Xin Fu
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