Production Of Antinuclear Antibodies Research Articles

TLR Tolerance Reduces IFN-Alpha Production Despite Plasmacytoid Dendritic Cell Expansion and Anti-Nuclear Antibodies in NZB Bicongenic Mice

Genetic loci on New Zealand Black (NZB) chromosomes 1 and 13 play a significant role in the development of lupus-like autoimmune disease. We have previously shown that C57BL/6 (B6) congenic mice with homozygous NZB chromosome 1 (B6.NZBc1) or 13 (B6.NZBc13) intervals develop anti-nuclear antibodies and mild glomerulonephritis (GN), together with increased T and B cell activation. Here, we produced B6.NZBc1c13 bicongenic mice with both intervals, and demonstrate several novel phenotypes including: marked plasmacytoid and myeloid dendritic cell expansion, and elevated IgA production. Despite these changes, only minor increases in anti-nuclear antibody production were seen, and the severity of GN was reduced as compared to B6.NZBc1 mice. Although bicongenic mice had increased levels of baff and tnf-α mRNA in their spleens, the levels of IFN-α-induced gene expression were reduced. Splenocytes from bicongenic mice also demonstrated reduced secretion of IFN-α following TLR stimulation in vitro. This reduction was not due to inhibition by TNF-α and IL-10, or regulation by other cellular populations. Because pDC in bicongenic mice are chronically exposed to nuclear antigen-containing immune complexes in vivo, we examined whether repeated stimulation of mouse pDC with TLR ligands leads to impaired IFN-α production, a phenomenon termed TLR tolerance. Bone marrow pDC from both B6 and bicongenic mice demonstrated markedly inhibited secretion of IFN-α following repeated stimulation with a TLR9 ligand. Our findings suggest that the expansion of pDC and production of anti-nuclear antibodies need not be associated with increased IFN-α production and severe kidney disease, revealing additional complexity in the regulation of autoimmunity in systemic lupus erythematosus.

Effect of narrow‐band ultraviolet B phototherapy on production of antinuclear antibodies

The Journal of DermatologyVolume 39, Issue 8 p. 733-734 LETTERS TO THE EDITOR Effect of narrow-band ultraviolet B phototherapy on production of antinuclear antibodies Amir R. HONARMAND, Amir R. HONARMAND Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorKamran BALIGHI, Kamran BALIGHI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorVahideh LAJEVARDI, Vahideh LAJEVARDI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorNasim POURTABATABAEI, Nasim POURTABATABAEI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorMajid BOREIRI, Majid BOREIRI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorEhsan AZIMI, Ehsan AZIMI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this author Amir R. HONARMAND, Amir R. HONARMAND Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorKamran BALIGHI, Kamran BALIGHI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorVahideh LAJEVARDI, Vahideh LAJEVARDI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorNasim POURTABATABAEI, Nasim POURTABATABAEI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorMajid BOREIRI, Majid BOREIRI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this authorEhsan AZIMI, Ehsan AZIMI Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, IranSearch for more papers by this author First published: 06 March 2012 https://doi.org/10.1111/j.1346-8138.2012.01519.xCitations: 3 Amir R. Honarmand, M.D., Razi Skin Hospital, Vahdate Eslami Square, Vahdate Esmlami Avenue, Tehran 11996, Iran. Email: [email protected] Conflict of interest: none. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume39, Issue8August 2012Pages 733-734 RelatedInformation

W5-2 Lymphopenia-induced proliferation (LIP) triggers the development of follicular helper T (T<sub>FH</sub>) cells which have a distinctive ontogeny and a critical role in aberrant B cell responses

Lymphopenia results in the homeostatic peripheral expansion of lymphocytes to maintain T cell homeostasis. Accumulating data show that lymphopenia-induced proliferation (LIP) has a pathogenic role in the development of autoimmunity in animal models and human systemic autoimmune diseases such as systemic lupus erythematosus, Sjögren's syndrome and rheumatoid arthritis. To clarify the mechanism of anti-nuclear antibodies (ANA) production, we established a lymphopenic mouse model in which CD4+ T cell subsets from wild-type BALB/c mice were adoptively injected into BALB/c nude mice, which induced IgG-type ANA production. We observed that class switching and ANA production were enhanced when regulatory T cells were depleted. We identified IL-21-producing PD-1+ TFH cells which develop from conventional T cells during LIP and drive germinal center reactions with aberrant B cell responses. Compared with traditional TFH cells, this subset has a distinctive ontogeny and a critical role in breaking B cell tolerance. This study reveals the physiological mechanism how immunological tolerance is maintained during LIP and would help to understand the pathogenesis of systemic autoimmune diseases.

Oxidative stress and endosome recycling are complementary mechanisms reorganizing the T-cell receptor signaling complex in SLE

Oxidative stress and endosome recycling are complementary mechanisms reorganizing the T-cell receptor signaling complex in SLE

Immunomodulatory Effects of Palifermin (Recombinant Human Keratinocyte Growth Factor) in an SLE‐Like Model of Chronic Graft‐Versus‐Host Disease

Keratinocyte growth factor (KGF) promotes epithelial cell proliferation and survival. Recombinant human KGF, also known as palifermin, protects epithelial cells from injury induced by chemicals, irradiation and acute murine graft-versus-host disease (GVHD). Findings from our studies and others have shown that palifermin also has immunomodulatory properties. In a model of acute GVHD, we showed that it shifts the immune response from one in which Th1 cytokines dominate to mixed Th1 and Th2 cytokine profile. Using the DBA/2→(C57BL/6 × DBA/2)F(1)-hybrid model of chronic, systemic lupus erythematosus-like GVHD, we showed that palifermin treatment is associated with higher levels of Th2 cytokines, the production of anti-nuclear antibodies, cryoglobulinemia and the development of more severe pathological changes in the kidney. The aim of our current study was to gain a better understanding of the immunobiology of KGF by further characterizing the palifermin-mediated effects in this model of chronic GVHD. Because the pathological changes we observed resemble those seen in thymic stromal lymphopoietin (TSLP) transgenic mice, we had originally hypothesized that palifermin might augment TSLP levels. Surprisingly, we did not observe an increase in thymic TSLP mRNA expression in palifermin-treated recipients. We did, however, observe some differences in the percentages of CD4(+) CD25(+) Foxp3(+) regulatory T cells in the spleen at some time points in palifermin-treated recipients. Most importantly, we found that TGFβ levels were higher in palifermin-treated recipients early in the GVH reaction, raising the possibility that KGF might indirectly induce the development of fibrosis and glomerulonephritis through a pathway involving TGFβ.

Loss of PKCδ results in characteristics of Sjögren’s syndrome including salivary gland dysfunction

Chronic infiltration of lymphocytes into the salivary and lacrimal glands of patients with Sjögren's syndrome (SS) leads to destruction of acinar cells and loss of exocrine function. Protein kinase C-delta (PKCδ) is known to play a critical role in B-cell maintenance. Mice in which the PKCδ gene has been disrupted have a loss of B-cell tolerance, multiple organ lymphocytic infiltration, and altered apoptosis. To determine whether PKCδ contributes to the pathogenesis of SS, we quantified changes in indicators of SS in PKCδ-/- mice as a function of age. Salivary gland histology, function, the presence of autoantibodies, and cytokine expression were examined. Submandibular glands were examined for the presence of lymphocytic infiltrates, and the type of infiltrating lymphocyte and cytokine deposition was evaluated by immunohistochemistry. Serum samples were tested by autoantibody screening, which was graded by its staining pattern and intensity. Salivary gland function was determined by saliva collection at various ages. PKCδ-/- mice have reduced salivary gland function, B220+ B-cell infiltration, anti-nuclear antibody production, and elevated IFN-γ in the salivary glands as compared to PKCδ+/+ littermates. PKCδ-/- mice have exocrine gland tissue damage indicative of a SS-like phenotype.

Genetic loci on New Zealand black chromosome 1 lead to increased generation of T follicular helper and TH17 cells (47.23)

Abstract Genetic loci on NZB c1 lead to antinuclear antibody (Ab) production and glomerulonephritis (GN). Using subcongenic lines, we found at least 5 genetic loci within a 35-106cM interval modulate disease. Notably, mice with a 70-100cM interval (c1(70-100cM)) develop high titre anti-dsDNA Ab, increased numbers of large germinal centers and severe GN a characteristic feature of lupus-prone mice with abnormalities of T follicular helper (TFH) and Th17 cells. In this study we determined whether variations in disease severity in c1 subcongenic mice are associated with differences in these subsets. The proportion of splenic TFH cells was significantly increased in c1(70-100) mice. Splenocytes from all c1 congenic mouse strains demonstrated increased production of IL-21 and IL-17 following anti-CD3/CD28 crosslinking which was greatest in c1(70-100) mice. The majority of IL-21 producing cells were TFH, many of which also secreted IFN-γ, but not IL-17. Immunization of 8-wk-old pre-autoimmune mice with ovalbumin (OVA) led to increased generation of TFH and Th17 cells in c1 (70-100) mice. This appeared to result in part from altered T cell function, as adoptively transferred OVA-specific TCR transgenic c1(70-100) T cells and naïve c1(70-100) T cells cultured in-vitro, demonstrated enhanced differentiation to TFH and IL-17-producing cells. Thus, genetic loci on NZB c1 promote differentiation of T cells to TFH and Th17 cells and this capacity correlates with the severity of disease.

The Current Concept of T H 17 Cells and Their Expanding Role in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a multifaceted range of symptoms affecting almost every organ system. The prototypical pathology of SLE involves the production of antinuclear antibodies and the deposition of immune complexes in basement membranes throughout the body where they induce inflammatory responses. The genetic and environmental etiologies of this process are being intensively sought, and recently, T H 17 cells have been implicated in the pathogenesis of SLE. T H 17 cells are CD4+ memory T cells that behave as both helper and effector cell populations functioning through their signature IL-17 cytokines. Their differentiation is distinct to either the T H 1 or T H 2 cell lineage, but strongly influences development of adaptive responses, including autoimmunity. This paper details the biological functions and regulation of T H 17 cells, followed by an update of their expanding role in SLE.

Dysregulated Generation of Follicular Helper T Cells in the Spleen Triggers Fatal Autoimmune Hepatitis in Mice

To clarify mechanisms involved in the development of autoimmune hepatitis (AIH), we recently developed a mouse model of spontaneous AIH by inducing a concurrent loss of Foxp3(+) regulatory T cells and programmed cell death 1 (PD-1)-mediated signaling. Fatal AIH in these mice was characterized by severe T-cell infiltration and huge production of antinuclear antibodies (Abs). This study aims to identify induction sites, responsible T-cell subsets, and key molecules for induction of AIH. To develop the mouse model of AIH, neonatal thymectomy (NTx) was performed on PD-1-deficient (PD-1(-/-)) mice. We then conducted neonatal splenectomy or in vivo administration of Abs to cytokines, chemokines, or cell-surface molecules. In NTx-PD-1(-/-) mice, either neonatal splenectomy or in vivo CD4(+) T-cell depletion suppressed CD4(+) and CD8(+) T-cell infiltration in the liver. In the induction phase of AIH, splenic CD4(+) T cells were localized in B-cell follicles with huge germinal centers and showed the Bcl6(+) inducible costimulator (ICOS)(+) interleukin (IL)-21(+) IL-21 receptor (IL-21R)(+) follicular helper T (T(FH)) cell phenotype. Blocking Abs to ICOS or IL-21 suppressed T(FH)-cell generation and induction of AIH. In addition, IL-21 produced by T(FH) cells drove CD8(+) T-cell activation. Splenic T(FH) cells and CD8(+) T cells expressed CCR6, and CCL20 expression was elevated in the liver. Administration of anti-CCL20 suppressed migration of these T cells to the liver and induction of AIH. Dysregulated T(FH) cells in the spleen are responsible for the induction of fatal AIH, and CCR6-CCL20 axis-dependent migration of splenic T cells is crucial to induce AIH in NTx-PD-1(-/-) mice.

Modulation of Lupus Phenotype by Adiponectin Deficiency in Autoimmune Mouse Models

Adiponectin is an adipocyte-derived cytokine with anti-inflammatory properties. Paradoxically, circulating adiponectin levels are increased in a number of inflammatory diseases. Thus, we sought to define the role of adiponectin deficiency in mouse models of autoimmunity. Adiponectin-deficient mice on a C57BL/6 background do not develop an autoimmune phenotype. Autoimmunity was also not observed in adiponectin-deficient mice generated on the permissive MRL background. However, adiponectin deficiency exacerbated the autoimmune phenotype of MRL-lpr mice. Compared with MRL-lpr mice, MRL-lpr.apn(-/-) mice displayed greater lymphadenopathy and splenomegaly, as well as increased anti-nuclear antibody and anti-dsDNA production. In addition, evaluation of the kidney revealed larger glomerular tuft size, crescent formation, increased IgG and C3 deposits, and mesangial expansion in the MRL-lpr.apn(-/-) mice. The effects of adiponectin deficiency on the autoimmune phenotypes were more pronounced in female versus male mice. These data show that, while adiponectin deficiency is not sufficient to confer autoimmunity, adiponectin acts as a negative modulator of the autoimmune phenotype in a murine model of lupus.

Murine lupus susceptibility locus Sle1a requires the expression of two sub-loci to induce inflammatory T cells

The NZM2410-derived Sle1a lupus susceptibility locus induces activated autoreactive CD4+ T cells and reduces the number and function of Foxp3+ regulatory T cells. In this study, we first showed that Sle1a contributes to autoimmunity by increasing anti-nuclear antibody production when expressed on either NZB or NZW heterozygous genomes, and by enhancing the chronic graft vs. host disease response indicating an expansion of the autoreactive B cell pool. Screening two non-overlapping recombinants, the Sle1a.1 and Sle1a.2 intervals that cover the entire Sle1a locus, revealed that both Sle1a.1 and Sle1a.2 were necessary for the full Sle1a phenotype. Sle1a.1, and to a lesser extent Sle1a.2, significantly affected CD4+ T cell activation as well as Treg differentiation and function. Sle1a.2 also increased the production of autoreactive B cells. Since the Sle1a.1 and Sle1a.2 intervals contain only one and 15 known genes, respectively, this study considerably reduces the number of candidate genes responsible for the production of autoreactive T cells. These results also demonstrate that the Sle1 locus is an excellent model for the genetic architecture of lupus, in which a major obligate phenotype results from the co-expression of multiple genetic variants with individual weak effects.

Analysis of HLA‐DRB1 polymorphisms in Japanese patients with primary biliary cirrhosis (PBC): The HLA‐DRB1polymorphism determines the relative risk of antinuclear antibodies for disease progression in PBC

Anti-gp210 and anti-centromere antibodies are different risk factors for the progression of primary biliary cirrhosis (PBC). However, the association of human leukocyte antigen (HLA) polymorphisms with these risk factors is unknown. We determined the HLA-DRB1 genotype in 334 Japanese PBC patients and studied their serum antibodies to gp210 and centromere during the 1-452-month observation period. Anti-gp210 (odds ratio [OR] 46.56, 95% confidence interval [CI], 9.20-850.1) and anti-centromere antibodies (OR, 2.36, 95% CI, 1.28-4.35) were significant risk factors for jaundice- and nonjaundice-type progression, respectively. HLA-DRB1*0405 and *0803 predisposed patients to anti-gp210 (OR, 1.61, 95% CI, 1.08-2.39) and anti-centromere (OR, 2.30, 95% CI, 1.41-3.73) antibody production, respectively. HLA-DRB1*1502 and *0901 patients were predisposed to nonjaundice-type progression (OR, 1.98, 95% CI, 1.13-3.40 and OR, 1.78, 95% CI, 1.02-3.03), while HLA-DRB1*0803 and *0405 patients were predisposed to disease development (OR, 2.24, 95% CI, 1.48-3.41 and OR, 1.53, 95% CI, 1.11-2.11, respectively). Stratifying patients by HLA-DRB1 alleles revealed that anti-gp210 antibodies was a strong risk factor, regardless of the HLA-DRB1 alleles for jaundice-type progression, while anti-centromere antibodies was a significant risk factor for nonjaundice-type progression in patients with HLA-DRB1*0405 (OR, 6.89, 95% CI, 2.18-26.56) and -DRB1*0803 (OR, 5.42, 95% CI, 1.47-24.62) but not other HLA-DRB1 alleles. HLA-DRB1 polymorphisms are significantly associated with not only disease development and progression but also antinuclear antibody production and the determination of the relative risk of antinuclear antibodies that contribute to PBC disease progression.

Olf1/EBF associated zinc finger protein interfered with antinuclear antibody production in patients with systemic lupus erythematosus

IntroductionThe aim of the study was to determine whether Olf1/EBF associated zinc finger protein (OAZ), a transcription factor encoded by a positional systemic lupus erythematosus (SLE) candidate gene, plays a functional role in the pathogenesis in SLE.MethodsGene expression levels in peripheral blood cells (PBLs) measured using quantitative real-time polymerase chain reaction (qPCR) were assessed for association with disease activity and the presence of specific autoantibodies. Peripheral blood mononuclear cells (PBMCs) were incubated with specific siRNAs for three days, then cells were harvested for measuring mRNA levels using qPCR, and supernatants for levels of total immunoglobulin (Ig)G and IgM as well as secreted cytokines, chemokine and antinuclear antibodies (ANA) using ELISA. Indirect immunofluorescence was also applied for ANA detection.ResultsOAZ gene expressions in PBLs from 40 ANA-positive SLE patients were significantly increased than those from 30 normal controls (P < 0.0001) and 18 patients with rheumatoid arthritis (P < 0.01). In SLE patients, OAZ transcripts were positively correlated with SLE disease activity index (SLEDAI) score (r = 0.72, P < 0.0001) and higher in those positive for anti-dsDNA or anti-Sm antibodies (both P < 0.05). Co-culturing with OAZ siRNAs reduced mRNA levels of OAZ by 74.6 ± 6.4% as compared to those co-cultured with non-targeting siRNA and OAZ silencing resulted in reduced total IgG, ANA, interferon (IFN)-γ, interleukin (IL)-10, IL-12 and IL-21, but elevated CCL2 levels in culture supernatants (P < 0.05). The declined ANA levels correlated with inhibited OAZ expression (r = 0.88, P = 0.05), reduced IL-21 levels (r = 0.99, P < 0.01), and elevated chemokine (C-C motif) ligand 2 levels (r = -0.98, P < 0.01). Expressions of ID1-3 were significantly down-regulated by 68.7%, 70.2% and 67.7% respectively after OAZ silence, while ID3 was also highly expressed in SLE PBLs (P < 0.0001) and associated with disease activity (r = 0.76, P < 0.0001) as well as anti-dsDNA or anti-Sm antibodies (both P < 0.05).ConclusionsElevated expression of OAZ transcripts in SLE PBLs were strongly correlated with disease activity. Suppression of OAZ expression inhibited downstream ID levels, and secretion of ANA and IL-21, implicating a role of OAZ pathway in the pathogenesis of SLE.

Modulation of nuclear factor‐κB activity can influence the susceptibility to systemic lupus erythematosus

Autoimmune diseases, such as systemic lupus erythematosus (SLE), result from deficiencies in self-antigen tolerance processes, which require regulated dendritic cell (DC) function. In this study we evaluated the phenotype of DCs during the onset of SLE in a mouse model, in which deletion of the inhibitory receptor FcgammaRIIb leads to the production of anti-nuclear antibodies and glomerulonephritis. Splenic DCs from FcgammaRIIb-deficient mice suffering from SLE showed increased expression of co-stimulatory molecules. Furthermore, diseased mice showed an altered function of the nuclear factor-kappaB (NF-kappaB) transcription factor, which is involved in DC maturation. Compared with healthy animals, expression of the inhibitory molecule IkappaB-alpha was significantly decreased in mice suffering from SLE. Consistently, pharmacological inhibition of NF-kappaB activity in FcgammaRIIb-deficient mice led to reduced susceptibility to SLE and prevented symptoms, such as anti-nuclear antibodies and kidney damage. Our data suggest that the occurrence of SLE is significantly influenced by alterations of NF-kappaB function, which can be considered as a new therapeutic target for this disease.

Induction of Autoimmunity in a Bleomycin-Induced Murine Model of Experimental Systemic Sclerosis: An Important Role for CD4+ T Cells

Systemic sclerosis (SSc) is an autoimmune disease characterized by the excessive deposition of collagen in the skin or other organs and the production of specific antinuclear antibodies (ANAs). Recently, bleomycin (BLM)-induced experimental scleroderma was reported in a murine model. Here, we present further development of this model and suggest that it is appropriate for the analysis of human diffuse type SSc. BLM was injected into the shaved backs of C3H or BALB/c mice (100 microg/mouse) 5 days per week for 3 weeks. Skin fibrosis was confirmed and pathological changes were seen in the lower part of the esophagus and stomach similar to those seen in SSc. The sera from these mice had autoantibodies specific to the damaged tissues and ANAs. Transfer of CD4(+) T cells from BLM-treated BALB/c mice induced the same pathological changes and antibody production in untreated-BALB/c nude mice. Hence, tissue fibrosis and the production of ANAs are probably associated with CD4(+) T-cell activity in this model. In conclusion, this model will be valuable for investigating the relationship between tissue fibrosis and abnormalities of the immune system.

Antigen-specific responses and ANA production in B6. Sle1b mice: A role for SAP

B6. Sle1b mice, which contain the Sle1b gene interval derived from lupus prone NZM2410 mice on a C57BL/6 background, present with gender-biased, highly penetrant anti-nuclear antibody (ANA) production. To obtain some insight into the possible induction mechanism of autoantibodies in these mice we compared antigen-specific T dependent (TD) and T independent (TI-II) responses between B6. Sle1b and B6 mice before the development of high ANA titers. Our results show that B6. Sle1b mice mount enhanced responses to a TI-II antigen. Additionally, the memory T cell response generated by a TD antigen also increased. This enhancement correlates with the greater ability of B cells from B6. Sle1b mice to present antigen to T cells. The SLAM Associated Protein (SAP) is critical for signaling of many of the molecules encoded by the SLAM/CD2 gene cluster, candidates for mediating the Sle1b phenotype; therefore, we also investigated the effect of sap deletion in these strains on the TD and TI-II responses as well as on ANA production. The results of these studies of responses to non-self-antigens provide further insight into the mechanism by which responses to self-antigens might be initiated in the context of specific genetic alterations.

Age-related autoantibody production in a nonhuman primate model.

Autoantibody production increases with ageing. However, the pathological significance of this increase as well as the corresponding underlying mechanisms are poorly understood. To further our understanding of the role that ageing plays in the development of autoantibody responses, we used a novel nonhuman primate model consisting of healthy baboons of ages representing the entire lifespan of this animal species. Results from this study indicate that production of antinuclear antibodies, anticell extract antibodies and natural autoantibodies gradually and significantly increases from young age to old age without a corresponding increase in neither serum immunoglobulin concentration nor in levels of selected markers of immune dysregulation (sTNF-RI, sTNF-RII, IL-2 sR alpha and IFN-gamma). Therefore, in the baboon model, autoantibodies may be produced in absence of recognizable pathological conditions of the ageing immune system.

Control of T Lymphocyte Signaling by Ly108, a Signaling Lymphocytic Activation Molecule Family Receptor Implicated in Autoimmunity

The signaling lymphocytic activation molecule family of receptors has been implicated in the pathophysiology of autoimmunity in humans and mice. One member of the family, Ly108, was strongly linked to lupus susceptibility in mice. High expression of a Ly108 isoform, Ly108-1, was observed in lymphocytes of lupus-prone mice. Herein, we examined the molecular basis for the influence of Ly108 on lupus susceptibility by studying Ly108 signal transduction in T cells. We observed that Ly108 was able to mediate a tyrosine phosphorylation signal implicating Ly108, Vav-1, and c-Cbl in a manner strictly dependent on engagement of the extracellular domain of Ly108 and co-expression of the Src homology 2 (SH2) domain-containing adaptor signaling lymphocytic activation molecule (SLAM)-associated protein (SAP). Evaluation of T cells from mice carrying mutations in the SAP-FynT pathway indicated that Ly108-triggered protein tyrosine phosphorylation was due to the capacity of SAP to recruit FynT. Importantly, Ly108-1 was more apt at triggering tyrosine phosphorylation signals in T cells when compared with the predominant Ly108 isoform found in non-lupus-prone mice, Ly108-2. This difference was due in part to the presence in Ly108-1 of a unique intra-cytoplasmic tyrosine-based motif that promoted Ly108 signal transduction. Together these data provided a molecular explanation for the involvement of Ly108 in lupus susceptibility in mice.

Temporary breakdown of immunological tolerance to dsDNA and nucleohistone antigens in rabbits infected with rinderpest virus

The rabbit-passaged L strain of rinderpest virus (RV) causes the transient induction of anti-nuclear antibodies (ANA) in rabbits. It has been shown by an indirect immunofluorescence test that the target antigens of these ANA are DNA and/or DNA-histone complexes (nucleohistone). Here detailed examinations of the target antigens were carried out by ELISA, and it was revealed that rabbit sera contained three types of antibodies: antibodies reacting equally with both dsDNA and ssDNA; those reacting with ssDNA alone; and those reacting with nucleohistone. Epitopes recognized by the third type consisted of complexes of dsDNA and H2A + H2B or of dsDNA and H2B. All types of antibodies were antigen specific. Since the diversity of ANA among experimental rabbits was large, it was suggested that genetic background is important in the induction of anti-dsDNA antibodies in this system. Moreover, early induction of antibodies to nucleohistone and the rapid disappearance of ANA suggest that B cell proliferation/maturation for continuous production of ANA requires factors other than RV infection. This system may help elucidate the mechanisms of ANA induction and the development of autoimmune diseases.

Fatal Autoimmune Hepatitis Induced by Concurrent Loss of Naturally Arising Regulatory T Cells and PD-1-Mediated Signaling

Because of the lack of animal models developing spontaneous autoimmune hepatitis (AIH), the molecular mechanisms involved in the development of AIH are still unclear. This study aims to examine the regulatory roles of naturally arising CD4(+)CD25(+) regulatory T (Treg) cells and programmed cell death 1 (PD-1)-mediated signaling in the development of AIH. To induce a concurrent loss of Treg cells and PD-1-mediated signaling, neonatal thymectomy (NTx), which severely reduces the number of Treg cells, was performed on PD-1(-/-) mice. After the NTx, we performed histologic examination, assessed autoantibody production and infiltrating cells in the liver, and conducted adoptive transfer experiments. In contrast to NTx mice and PD-1(-/-) mice, NTx-PD-1(-/-) mice produced antinuclear antibodies and developed fatal hepatitis characterized by a CD4(+) and CD8(+) T-cell infiltration invading the parenchyma with massive lobular necrosis. Induction of AIH in NTx-PD-1(-/-) mice was suppressed by transfer of Treg cells, even derived from PD-1(-/-) mice. Transfer of total but not CD4(+) T-cell-depleted splenocytes from NTx-PD-1(-/-) mice into RAG2(-/-) mice induced the development of severe hepatitis. In contrast, the transfer of CD8(+) T-cell-depleted splenocytes triggered only mononuclear infiltrates without massive necrosis of the parenchyma. NTx-PD-1(-/-) mice are the first mouse model of spontaneous fatal AIH. The concurrent loss of Treg cells and PD-1-mediated signaling can induce the development of fatal AIH. Autoreactive CD4(+) T cells are essential for induction of AIH, whereas CD8(+) T cells play an important role in progression to fatal hepatic damage.