Disparate T cell requirements of two subsets of lupus-specific autoantibodies in pristane-treated mice

HDAC6 Deletion Decreases Pristane-induced Inflammation

Systemic lupus erythematosus is an autoimmune disease characterized by excessive inflammation and production of pathogenic Abs. Histone deacetylase 6 (HDAC6) is a class IIb histone deacetylase. It has been reported that selective HDAC6 inhibition decreases inflammation in lupus mouse models. In this study, sex- and age-matched wild-type (WT) and HDAC6-/- mice on the C57BL/6 background were administered 0.5 ml of pristane or PBS i.p. at 8-12 wk of age and were euthanized 10 d later. At sacrifice, body weight and spleen weight were measured, sera were collected, and splenocytes and peritoneal cells were harvested for flow cytometry. We found pristane administration increased the spleen weight with no difference between WT and HDAC6-/- mice. Pristane administration promoted the population of CD11b+Ly6C++ inflammatory monocytes and CD11b+Ly6G+ neutrophils. Peritoneal recruitment of these inflammatory monocytes and neutrophils was significantly decreased in HDAC6-/- mice compared with the WT mice. Flow cytometry results showed that the number of CD69+ T and B cells was increased in HDAC6-/- mice. Pristane administration also induced the IFN signature genes as determined by RT-qPCR. Furthermore, IFN signature genes were not affected in HDAC6-/- mice compared with the WT mice. In vitro studies in J774A.1 cells revealed that the selective HDAC6 inhibitor (ACY-738) increased acetylation of NF-κB while increasing Stat1 phosphorylation, which resulted in inducible NO synthase production in LPS/IFN-γ-stimulated cells. Taken together, these results demonstrate that although HDAC6 inhibition may inhibit some inflammatory pathways, others remain unaffected.

Research progress of SIRTs activator resveratrol and its derivatives in autoimmune diseases

Autoimmune diseases (AID) have emerged as prominent contributors to disability and mortality worldwide, characterized by intricate pathogenic mechanisms involving genetic, environmental, and autoimmune factors. In response to this challenge, a growing body of research in recent years has delved into genetic modifications, yielding valuable insights into AID prevention and treatment. Sirtuins (SIRTs) constitute a class of NAD-dependent histone deacetylases that orchestrate deacetylation processes, wielding significant regulatory influence over cellular metabolism, oxidative stress, immune response, apoptosis, and aging through epigenetic modifications. Resveratrol, the pioneering activator of the SIRTs family, and its derivatives have captured global scholarly interest. In the context of AID, these compounds hold promise for therapeutic intervention by modulating the SIRTs pathway, impacting immune cell functionality, suppressing the release of inflammatory mediators, and mitigating tissue damage. This review endeavors to explore the potential of resveratrol and its derivatives in AID treatment, elucidating their mechanisms of action and providing a comprehensive analysis of current research advancements and obstacles. Through a thorough examination of existing literature, our objective is to advocate for the utilization of resveratrol and its derivatives in AID treatment while offering crucial insights for the formulation of innovative therapeutic approaches.

Leptin- and cytokine-like unpaired signaling in Drosophila

Animals have evolved a multitude of signaling pathways that enable them to orchestrate diverse physiological processes to tightly regulate systemic homeostasis. This signaling is mediated by various families of peptide hormones and cytokines that are conserved across the animal kingdom. In this review, we primarily focus on the unpaired (Upd) family of proteins in Drosophila which are evolutionarily related to mammalian leptin and the cytokine interleukin 6. We summarize expression patterns of Upd in Drosophila and discuss the parallels in structure, signaling pathway, and functions between Upd and their mammalian counterparts. In particular, we focus on the roles of Upd in governing metabolic homeostasis, growth and development, and immune responses. We aim to stimulate future studies on leptin-like signaling in other phyla which can help bridge the evolutionary gap between insect Upd and vertebrate leptin and cytokines like interleukin 6.

Host genetics but not commensal microbiota determines the initial development of systemic autoimmune disease in BXD2 mice

OBJECTIVE

To determine the extent of gut microbiome in influencing systemic autoimmunity, we generated germ-free (GF) BXD2 lupus mice, which otherwise develop spontaneous germinal centers (GCs) and high titers of serum autoantibodies.

METHODS

The GF status was confirmed by gut bacterial culture. The autoimmune phenotypes in 6- and 12-mo-old gnotobiotic GF BXD2 mice and specific pathogen-free (SPF) BXD2 mice were compared. Serum levels of autoantibody were measured using ELISA. Histologic sections of kidney and joints were evaluated. Flow cytometry was used to analyze GC and age-associated B cells (ABCs). CD4⁺ T cells were analyzed for PD-1⁺ ICOS⁺ activated T cells, follicular T-regulatory cells (Tfr, Foxp3⁺ CD25⁺ PD-1⁺ CXCR5⁺ ), and PMA/ionomycin stimulated IL-17A⁺ or interferon-gamma (IFN-&ip.gamma;)⁺ PD-1⁺ ICOS⁺ T cells.

RESULTS

At 6-mo of age, the GF status did not affect splenomegaly, GC B cells, ABCs or serum autoantibodies except for IgG anti-histone. GF BXD2 mice exhibited a significantly higher percent of Tfr cells, compared to the SPF counterpart. At 12-mo-old, however, there were significantly diminished IgG autoantibodies and a lower percent of GC B cells and ABCs in GF BXD2 mice. Following stimulation, PD-1⁺ ICOS⁺ CD4 T cells expressed significantly lower IL-17A but not IFN-&ip.gamma; in GF BXD2 mice, compared to SPF mice. Both SPF and GF BXD2 mice developed equivalent renal and joint disease with no significant differences in severity.

CONCLUSION

Our results suggest a model in which genetics play a dominant role in determining the initial development of autoimmunity. In contrast, gut microbiomes may regulate the persistence of certain aspects of systemic autoimmunity.

IL-6 in inflammation, autoimmunity and cancer

IL-6 is involved both in immune responses and in inflammation, hematopoiesis, bone metabolism and embryonic development. IL-6 plays roles in chronic inflammation (closely related to chronic inflammatory diseases, autoimmune diseases and cancer) and even in the cytokine storm of corona virus disease 2019 (COVID-19). Acute inflammation during the immune response and wound healing is a well-controlled response, whereas chronic inflammation and the cytokine storm are uncontrolled inflammatory responses. Non-immune and immune cells, cytokines such as IL-1β, IL-6 and tumor necrosis factor alpha (TNFα) and transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play central roles in inflammation. Synergistic interactions between NF-κB and STAT3 induce the hyper-activation of NF-κB followed by the production of various inflammatory cytokines. Because IL-6 is an NF-κB target, simultaneous activation of NF-κB and STAT3 in non-immune cells triggers a positive feedback loop of NF-κB activation by the IL-6-STAT3 axis. This positive feedback loop is called the IL-6 amplifier (IL-6 Amp) and is a key player in the local initiation model, which states that local initiators, such as senescence, obesity, stressors, infection, injury and smoking, trigger diseases by promoting interactions between non-immune cells and immune cells. This model counters dogma that holds that autoimmunity and oncogenesis are triggered by the breakdown of tissue-specific immune tolerance and oncogenic mutations, respectively. The IL-6 Amp is activated by a variety of local initiators, demonstrating that the IL-6-STAT3 axis is a critical target for treating diseases.

Adjuvants- and vaccines-induced autoimmunity: animal models

The emergence of autoimmunity after vaccination has been described in many case reports and series. Everyday there is more evidence that this relationship is more than casual. In humans, adjuvants can induce non-specific constitutional, musculoskeletal or neurological clinical manifestations and in certain cases can lead to the appearance or acceleration of an autoimmune disease in a subject with genetic susceptibility. The fact that vaccines and adjuvants can trigger a pathogenic autoimmune response is corroborated by animal models. The use of animal models has enabled the study of the effects of application of adjuvants in a homogeneous population with certain genetic backgrounds. In some cases, adjuvants may trigger generalized autoimmune response, resulting in multiple auto-antibodies, but sometimes they can reproduce human autoimmune diseases including rheumatoid arthritis, systemic lupus erythematosus, Sjögren syndrome, autoimmune thyroiditis and antiphospholipid syndrome and may provide insights about the potential adverse effects of adjuvants. Likewise, they give information about the clinical, immunological and histologic characteristics of autoimmune diseases in many organs, especially secondary lymphoid tissue. Through the description of the physiopathological characteristics of autoimmune diseases reproduced in animal models, new treatment targets can be described and maybe in the future, we will be able to recognize some high-risk population in whom the avoidance of certain adjuvants can reduce the incidence of autoimmune diseases, which typically results in high morbidity and mortality in young people. Herein, we describe the main animal models that can reproduce human autoimmune diseases with emphasis in how they are similar to human conditions.

Pristane-induced lupus: considerations on this experimental model

Systemic lupus erythematosus (SLE) is a multifactorial, autoimmune inflammatory disease with pleomorphic clinical manifestations involving different organs and tissues. The etiology of this disease has been associated with a dysfunctional response of B and T lymphocytes against environmental stimuli in individuals genetically susceptible to SLE, which determines an immune response against different autoantigens and, consequently, tissue damage. The study of different murine models has provided a better understanding of these autoimmune phenomena. This review primarily focuses on that has been learned from the pristane-induced lupus (PIL) model and how this model can be used to supplement recent advances in understanding the pathogenesis of SLE. We also consider both current and future therapies for this disease. The PubMed, SciELO, and Embase databases were searched for relevant articles published from 1950 to 2016. PIL has been shown to be a useful tool for understanding the multiple mechanisms involved in systemic autoimmunity. In addition, it can be considered an efficient model to evaluate the environmental contributions and interferon signatures present in patients with SLE.

RORγt expression in Tregs promotes systemic lupus erythematosus via IL-17 secretion, alteration of Treg phenotype and suppression of Th2 responses

Systemic lupus erythematosus (SLE) is a common autoimmune disorder with a complex and poorly understood immunopathogenesis. However, a pathogenic role for the T helper type 17 (Th17) axis was demonstrated by many studies, while regulatory T cells (T_regs ) were shown to mediate protection. Recently, we and others characterized a novel and independent T cell population expressing both the T_reg characteristic transcription factor forkhead box protein 3 (FoxP3) and the Th17-defining retinoic acid receptor-related orphan nuclear receptor γt (RORγt). Studies in a model of acute glomerulonephritis unveiled potent regulatory, but also proinflammatory, functions of RORγt⁺ FoxP3⁺ T_regs . This bi-functional nature prompted us to suggest the name 'biT_regs '. Importantly, the pathogenic biT_reg effects were dependent upon expression of RORγt. We thus aimed to evaluate the contribution of RORγt⁺ FoxP3⁺ biT_regs to pristane-induced SLE and explored the therapeutic potential of interference with RORγt activation. Our analyses revealed expansion of IL-17 producing biT_regs in a distinctive time-course and organ-specific pattern, coincident with the development of autoimmunity and tissue injury. Importantly, specific ablation of RORγt activation in endogenous biT_regs resulted in significant amelioration of pristane-induced pulmonary vasculitis and lupus nephritis. As potential mechanisms underlying the observed protection, we found that secretion of IL-17 by biT_regs was abrogated completely in FoxP3^Cre  × RORC^fl/fl mice. Furthermore, T_regs showed a more activated phenotype after cell-specific inactivation of RORγt signalling. Finally, and remarkably, biT_regs were found to potently suppress anti-inflammatory Th2 immunity in a RORγt-dependent manner. Our study thus identifies biT_regs as novel players in SLE and advocates RORγt-directed interventions as promising therapeutic strategies.

Immune regulation by Fcα/μ receptor (CD351) on marginal zone B cells and follicular dendritic cells

Although both Fcα/μ receptor (Fcα/μR) and polymeric Ig receptor (poly-IgR) are Fc receptors for IgA and IgM and are functionally and genetically related, the expression profile of Fcα/μR is unique. Unlike poly-IgR, Fcα/μR is expressed on marginal zone (MZ) B cells and follicular dendritic cells, suggesting that Fcα/μR plays an important role in humoral immune responses. Fcα/μR mediates endocytosis of the IgM immune complex (IC). Recent research demonstrated that Fcα/μR downregulated retention of the IgM IC with a T-independent (TI) antigen on MZ B cells and follicular dendritic cells due to endocytosis of the IgM IC, suppressing germinal center formation, affinity maturation, and memory B-cell generation in response to TI antigen challenge. In addition, Fcα/μR physically associates with Toll-like receptor 4 (TLR4) and augments TLR4 oligomerization and signaling in MZ B cells upon lipopolysaccharide (LPS) challenge, leading to increased proinflammatory cytokine production by MZ B cells. Thus, Fcα/μR is a unique Fc receptor that is involved in humoral immune responses and inflammation.

Resveratrol possesses protective effects in a pristane-induced lupus mouse model

Background

Systemic lupus erythematosus (SLE) is a multisystemic autoimmune disease characterized by the production of autoantibodies. To date, no therapy has been found to satisfactorily treat SLE. SIRT1 deficiency results in the development of an autoimmune syndrome in mice, including a high titer of anti-nuclear antibody in serum, immunoglobulin deposition in the kidney, and immune complex glomerulonephritis. Resveratrol is an activator of SIRT1 and possesses anti-inflammation and immune-regulatory properties.

Objective

To evaluate the preventative effects of resveratrol on a pristane-induced lupus animal model and assess its putative immune modulation effects.

Methods

BALB/c mice received a single intraperitoneal injection of 0.5 ml of pristane on day 1 and then various doses of resveratrol were given to the mice daily starting on day 2 and continuing for seven months. The autoantibodies in serum and supernatants were measured. Single cells isolated from spleen, isolated CD4+ T cells, and CD19+ B cells were cultured with or without resveratrol in vitro and assessed by flow cytometry.

Results

Resveratrol attenuated proteinuria, immunoglobuin depositon in kidney, and glomerulonephritis as well as IgG1 and IgG2a in serum in pristane-induced lupus mice. Resveratrol also suppressed CD69 and CD71 expression on CD4+ T cells as well as CD4+ T cell proliferation, induced CD4+ T cell apoptosis, and decreased CD4 IFNγ⁺ Th1 cells and the ratio of Th1/Th2 cells in vitro. In vitro antibody production and proliferation of B cells were also inhibited.

Conclusion

Resveratrol possesses protective effects in pristane-induced lupus mice and may represent a novel approach for the management of SLE.

Endogenous interleukin (IL)-17A promotes pristane-induced systemic autoimmunity and lupus nephritis induced by pristane

Interleukin (IL)-17A is increased both in serum and in kidney biopsies from patients with lupus nephritis, but direct evidence of pathogenicity is less well established. Administration of pristane to genetically intact mice results in the production of autoantibodies and proliferative glomerulonephritis, resembling human lupus nephritis. These studies sought to define the role of IL-17A in experimental lupus induced by pristane administration. Pristane was administered to wild-type (WT) and IL-17A(-/-) mice. Local and systemic immune responses were assessed after 6 days and 8 weeks, and autoimmunity, glomerular inflammation and renal injury were measured at 7 months. IL-17A production increased significantly 6 days after pristane injection, with innate immune cells, neutrophils (Ly6G(+)) and macrophages (F4/80(+)) being the predominant source of IL-17A. After 8 weeks, while systemic IL-17A was still readily detected in WT mice, the levels of proinflammatory cytokines, interferon (IFN)-γ and tumour necrosis factor (TNF) were diminished in the absence of endogenous IL-17A. Seven months after pristane treatment humoral autoimmunity was diminished in the absence of IL-17A, with decreased levels of immunoglobulin (Ig)G and anti-dsDNA antibodies. Renal inflammation and injury was less in the absence of IL-17A. Compared to WT mice, glomerular IgG, complement deposition, glomerular CD4(+) T cells and intrarenal expression of T helper type 1 (Th1)-associated proinflammatory mediators were decreased in IL-17A(-/-) mice. WT mice developed progressive proteinuria, but functional and histological renal injury was attenuated in the absence of IL-17A. Therefore, IL-17A is required for the full development of autoimmunity and lupus nephritis in experimental SLE, and early in the development of autoimmunity, innate immune cells produce IL-17A.

Maintenance of anti-Sm/RNP autoantibody production by plasma cells residing in ectopic lymphoid tissue and bone marrow memory B cells

Although ectopic lymphoid tissue formation is associated with many autoimmune diseases, it is unclear whether it serves a functional role in autoimmune responses. 2,6,10,14-Tetramethylpentadecane causes chronic peritoneal inflammation and lupus-like disease with autoantibody production and ectopic lymphoid tissue (lipogranuloma) formation. A novel transplantation model was used to show that transplanted lipogranulomas retain their lymphoid structure over a prolonged period in the absence of chronic peritoneal inflammation. Recipients of transplanted lipogranulomas produced anti-U1A autoantibodies derived exclusively from the donor, despite nearly complete repopulation of the transplanted lipogranulomas by host lymphocytes. The presence of ectopic lymphoid tissue alone was insufficient, as an anti-U1A response was not generated by the host in the absence of ongoing peritoneal inflammation. Donor-derived anti-U1A autoantibodies were produced for up to 2 mo by plasma cells/plasmablasts recruited to the ectopic lymphoid tissue by CXCR4. Although CD4(+) T cells were not required for autoantibody production from the transplanted lipogranulomas, de novo generation of anti-U1A plasma cells/plasmablasts was reduced following T cell depletion. Significantly, a population of memory B cells was identified in the bone marrow and spleen that did not produce anti-U1A autoantibodies unless stimulated by LPS to undergo terminal differentiation. We conclude that 2,6,10,14-tetramethylpentadecane promotes the T cell-dependent development of class-switched, autoreactive memory B cells and plasma cells/plasmablasts. The latter home to ectopic lymphoid tissue and continue to produce autoantibodies after transplantation and in the absence of peritoneal inflammation. However, peritoneal inflammation appears necessary to generate autoreactive B cells de novo.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

TLR9 and TLR4 are required for the development of autoimmunity and lupus nephritis in pristane nephropathy

Systemic lupus erythematosus is a common autoimmune disease, with kidney involvement a serious complication associated with poor prognosis. Humoral immune responses constitute the hallmark of disease, however T helper cells are required for the generation of autoantibodies, as well as the induction and progression of renal injury. Administration of pristane to genetically intact mice results in the development of hypergammaglobulinaemia with the production of lupus like autoantibodies and proliferative glomerulonephritis, with similarities to human lupus nephritis. TLRs are intricately linked to the development of autoimmunity and are involved in the development of lupus nephritis. We injected wild type, TLR9-/- and TLR4-/- mice with pristane and assessed cellular and humoral autoimmunity and renal injury, 8 months later. TLR9-/- mice demonstrated a predominant decrease in Th1 cytokine production which resulted in decreased anti-RNP antibody levels, while anti-dsDNA levels remained intact. Compared to wild type mice treated with pristane, functional and histological renal injury and glomerular immunoglobulin and complement deposition was decreased in TLR9-/- mice. TLR4-/- mice demonstrated a global decrease in both Th1, IFNγ, and Th17 associated IL-17A and IL-6 cytokine production. Autoantibody levels of anti-dsDNA and anti-RNP were both decreased. Renal injury was attenuated in TLR4-/- mice which demonstrated less glomerular immunoglobulin and complement deposition. These results demonstrate that both TLR9 and TLR4 are required for 'full-blown' autoimmunity and organ injury in experimental lupus induced by pristane.

Induction of autoimmunity by pristane and other naturally occurring hydrocarbons

Tetramethylpentadecane (TMPD, or commonly known as pristane)-induced lupus is a murine model of systemic lupus erythematosus (SLE). Renal disease and autoantibody production strictly depend on signaling through the interferon (IFN)-I receptor. The major source of IFN-I is immature monocytes bearing high levels of the surface marker Ly6C. Interferon production is mediated exclusively by signaling through TLR7 and the adapter protein MyD88. It is likely that endogenous TLR7 ligands such as components of small nuclear ribonucleoprotein complexes are involved in triggering disease. Lupus autoantibodies are produced in ectopic lymphoid tissue developing in response to TMPD. This model is well suited for examining links between dysregulated IFN-I production and the pathogenesis of human SLE, which like TMPD-lupus, is associated with high levels of IFN-I.

Cluster of systemic lupus erythematosus (SLE) associated with an oil field waste site: a cross sectional study

BACKGROUND

This is a community comparison study that examines persons living in a subdivision exposed to petroleum products and mercury.

METHODS

We compared their health status and questionnaire responses to those living in another community with no known exposures of this type.

RESULTS

Pristane house dust among the exposed homes was higher than in the comparison communities. The exposed subdivision has higher ambient air mercury levels compared to the control community. The prevalence of rheumatic diseases (OR = 10.78; CI = 4.14, 28.12) and lupus (OR = 19.33; CI = 1.96, 190.72) was greater in the exposed population compared to the unexposed. A higher prevalence of neurological symptoms, respiratory symptoms and several cardiovascular problems including stroke (OR = 15.41; CI = 0.78, 304.68) and angina (OR = 5.72; CI = 1.68, 19.43) was seen.

CONCLUSION

There were statistically significant differences in B cells, Natural Killer Cells, gamma glutamyl transferase, globulin and serum calcium levels between control and exposed subjects.

Anti-interleukin-6 monoclonal antibody inhibits autoimmune responses in a murine model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease resulting from dysregulation of the immune system. Interleukin-6 (IL-6) is a multifunctional cytokine produced by macrophages, monocytes and T and B cells. It stimulates B-cell differentiation/maturation, immunoglobulin secretion, and T-cell functions. Elevated levels of IL-6 in serum, urine and renal glomeruli were detected in patients with active SLE and in murine models of SLE. Our study investigated the role of IL-6 in an SLE-like disease in New Zealand Black/White (NZB/W) F1 mice by administration of an anti-murine IL-6 monoclonal antibody (mAb). Intraperitoneal administration of the anti-IL-6 mAb suppressed the production of anti-dsDNA autoantibody. B-cell proliferation induced by anti-IgM and anti-CD40 was lower in the anti-IL-6 mAb-treated mice, ex vivo studies demonstrated that anti-IL-6 mAb treatment inhibited anti-dsDNA production. Anti-CD3-induced T-cell proliferation and mixed lymphocyte reactions were inhibited by anti-IL-6 mAb treatment, indicating a partial down-regulation of T cells. Histological analysis showed that treatment with anti-IL-6 mAb prevented the development of severe kidney disease. These results suggest that treatment with anti-IL-6 mAb has a beneficial effect on autoimmunity in murine SLE and that autoreactive B cells may be the primary target for anti-IL-6 mAb treatment; its effect on autoreactive T cells is also indicated.

Interleukin-6: discovery of a pleiotropic cytokine

In the late 1960s, the essential role played by T cells in antibody production was reported. This led to our hypothesis that certain molecules would have to be released from T cells to effect the stimulation of B cells. This hypothesis was shown to be true. There were certain factors present in the culture supernatant of T cells that induced proliferation and differentiation of B cells. The factor that induced B cells to produce immunoglobulins was initially named B cell stimulatory factor-2. The cDNA encoding the human B cell stimulatory factor-2 was cloned in 1986. At the same time, IFN-β₂ and a 26 kDa protein in the fibroblasts were independently cloned and found to be identical to B cell stimulatory factor-2. Later, a hybridoma/plasmacytoma growth factor and a hepatocyte stimulating factor were also proven to be the same molecule as B cell stimulatory factor-2. Various names were used for this single molecule because of its multiple biological activities, but these have all been unified and the molecule is now known as IL-6. Since the discovery of IL-6, rapid progress has been made in our understanding of IL-6 activities, the IL-6 receptor system and the IL-6 signal transduction mechanism. More importantly, it has been shown to be involved in a number of diseases such as rheumatoid arthritis and Castleman's disease. When taking into account all the accumulated basic research on the various aspects of this molecule, it appeared that blocking the activity of IL-6 was a feasible, new therapeutic approach for chronic inflammatory diseases.

Induction of apoptosis by the hydrocarbon oil pristane: implications for pristane-induced lupus

Intraperitoneal injection of the hydrocarbon oil pristane into normal mice leads to a lupus-like autoimmune syndrome. Although advances in defining the roles of cellular and humoral mediators involved in this syndrome have been made, the mechanisms that initiate a break in tolerance leading to autoimmunity remain unknown. We describe in this study that pristane induces apoptosis both in vivo and in vitro. Pristane arrests cell growth and induces cell death by apoptosis via the mitochondrial pathway of caspase activation in a dose-dependent manner. Nuclear autoantigens created by pristane-induced apoptosis of lymphoid cells within the peritoneal cavity in the setting of a profoundly altered cytokine milieu may be the initiating event in the development of autoimmunity in this syndrome. These findings suggest that apoptosis may be a critical initial event in the pathogenesis of pristane-induced lupus and are of potential relevance for human systemic lupus erythematosus.

Infliximab, but not etanercept, induces IgM anti-double-stranded DNA autoantibodies as main antinuclear reactivity: biologic and clinical implications in autoimmune arthritis

OBJECTIVE

To analyze the clinical and biologic correlates of autoantibody induction during longer-term tumor necrosis factor alpha (TNFalpha) blockade with either the monoclonal antibody infliximab or the soluble receptor etanercept.

METHODS

Thirty-four patients with spondylarthropathy (SpA) and 59 patients with rheumatoid arthritis (RA) were treated with infliximab for 2 years. Additionally, 20 patients with SpA were treated with etanercept for 1 year. Sera were blindly analyzed for antinuclear antibodies (ANAs), anti-double-stranded DNA (anti-dsDNA) antibodies, anti-extractable nuclear antigen (anti-ENA) antibodies, and antihistone, anti-nucleosome, and anticardiolipin antibodies (aCL). The anti-dsDNA antibodies were isotyped.

RESULTS

High numbers of infliximab-treated patients with SpA or RA had newly induced ANAs (61.8% and 40.7%, respectively) and anti-dsDNA antibodies (70.6% and 49.2%, respectively) after 1 year, but no further increase between year 1 and year 2 was observed. In contrast, induction of ANAs and anti-dsDNA antibodies was observed only occasionally in the etanercept-treated patients with SpA (10% of patients each). Isotyping revealed almost exclusively IgM or IgM/IgA anti-dsDNA antibodies, which disappeared upon interruption of treatment. Neither infliximab nor etanercept induced other lupus-related reactivities such as anti-ENA antibodies, antihistone antibodies, or anti-nucleosome antibodies, and no clinically relevant lupus-like symptoms were observed. Similarly, infliximab but not etanercept selectively increased IgM but not IgG aCL titers.

CONCLUSION

The prominent ANA and anti-dsDNA autoantibody response is not a pure class effect of TNFalpha blockers, is largely restricted to short-term IgM responses, and is not associated with other serologic or clinical signs of lupus. Similar findings with aCL suggest that modulation of humoral immunity may be a more general feature of infliximab treatment.

Autoimmunity induced by adjuvant hydrocarbon oil components of vaccine

Adjuvant oils such as Bayol F (Incomplete Freund's adjuvant: IFA) and squalene (MF59) have been used in human and veterinary vaccines despite poor understanding of their mechanisms of action. Several reports suggest an association of vaccination and various autoimmune diseases, however, few were confirmed epidemiologically and the risk of vaccination for autoimmune diseases has been considered minimal. Microbial components, not the adjuvant components, are considered to be of primary importance for adverse effects of vaccines. We have reported that a single intraperitoneal injection of the adjuvant oils pristane, IFA or squalene induces lupus-related autoantibodies to nRNP/Sm and -Su in non-autoimmune BALB/c mice. Induction of these autoantibodies appeared to be associated with the hydrocarbon's ability to induce IL-12, IL-6, and TNF-alpha, suggesting a relationship with hydrocarbon's adjuvanticity. Whether this is relevant in human vaccination is a difficult issue due to the complex effects of vaccines and the fact that immunotoxicological effects vary depending on species, route, dose, and duration of administration. Nevertheless, the potential of adjuvant hydrocarbon oils to induce autoimmunity has implications in the use of oil adjuvants in human and veterinary vaccines as well as basic research.

IL-6 in autoimmune disease and chronic inflammatory proliferative disease

Interleukin 6 (IL-6), which was originally identified as a B-cell differentiation factor, is now known to be a multifunctional cytokine that regulates the immune response, hematopoiesis, the acute phase response, and inflammation. Deregulation of IL-6 production is implicated in the pathology of several disease processes. The expression of constitutively high levels of IL-6 in transgenic mice results in fatal plasmacytosis, which has been implicated in human multiple myeloma. Increased IL-6 levels are also observed in several diseases, including rheumatoid arthritis (RA), systemic-onset juvenile chronic arthritis (JCA), osteoporosis, and psoriasis. IL-6 is critically involved in experimentally induced autoimmune disease, such as antigen-induced arthritis (AIA), and experimental allergic encephalomyelitis. All these clinical data and animal models suggest that IL-6 plays critical roles in the pathogenesis of autoimmune diseases. Here we review the evidence for the involvement of IL-6 in the pathophysiology of autoimmune diseases and chronic inflammatory proliferative diseases (CIPD) and discuss the possible molecular mechanisms of its involvement.

Interferon-gamma is required for lupus nephritis in mice treated with the hydrocarbon oil pristane

BACKGROUND

Although the precise mechanisms leading to lupus nephritis remain obscure, both TH1 and TH2 cytokines have been implicated. The present study examined the roles of interleukin (IL)-4 and interferon-gamma (IFN-gamma) in a novel inducible form of lupus that develops in non-autoimmune mice treated with the hydrocarbon oil pristane.

METHODS

BALB/c IL-4 or IFN-gamma deficient mice (IL-4 -/-, IFNgamma -/-) and wild type controls (+/+) received either pristane or phosphate-buffered saline (PBS) IP. Serial sera were analyzed for anti-DNA/chromatin, anti-RNP/Sm, and total immunoglobulin levels. Proteinuria was measured and kidneys were examined by direct immunofluorescence and light microscopy.

RESULTS

Renal disease did not develop in pristane-treated IFN-gamma -/- mice, as assessed by the absence of capillary immune deposits, glomerular pathology and proteinuria whereas IL-4 -/- mice developed renal disease similar to +/+ mice. Production of IgG anti-single stranded DNA and anti-chromatin antibodies was abrogated in IFN-gamma -/- mice. In contrast, these autoantibodies were produced at similar or higher frequencies and levels by IL-4 -/- versus wild-type mice. The frequency of anti-nRNP/Sm was markedly reduced in IFN-gamma -/- mice. IL-4 deficiency had little effect on the production of anti-DNA/chromatin and anti-nRNP/Sm.

CONCLUSIONS

IFN-gamma is essential for the induction of nephritis and anti-DNA/chromatin following pristane exposure in BALB/c mice, suggesting that genetic or environmental factors influencing TH1-TH2 balance could be an important determinant of renal disease in lupus.

Fas and Fas ligand mutations inhibit autoantibody production in pristane-induced lupus

Mutations of Fas (lpr) or Fas ligand (gld) cause a limited lupus-like syndrome in B6 mice by interfering with the deletion of autoreactive B and/or T cells. A more generalized lupus syndrome reminiscent of that of MRL mice can be induced in nonautoimmune strains by pristane, which causes a nonspecific inflammatory response in the peritoneal cavity. We hypothesized that, as in MRL mice, the lpr and gld mutations might accelerate lupus in pristane-treated mice. Pristane-treated B6 mice developed anti-nRNP/Sm, Su, and ribosomal P Abs, but little anti-ssDNA or chromatin. In contrast, B6/lpr and B6/gld mice spontaneously developed anti-ssDNA/chromatin Abs, but not anti-nRNP/Sm/Su/ribosomal P. Unexpectedly, B6/lpr and B6/gld mice were highly resistant to the induction by pristane of IgM anti-ssDNA (2 wk) and IgG anti-nRNP/Sm/Su/ribosomal P autoantibodies (6 mo), suggesting that intact Fas signaling is necessary. Interestingly, pristane did not enhance IgG chromatin Ab production in B6/lpr or B6/gld mice, suggesting that it did not influence the production of autoantibodies that develop spontaneously in the setting of Fas deficiency. Pristane treatment also decreased lymphoproliferation in B6/lpr mice. Increased production of IL-12 was associated consistently with the production of anti-nRNP/Sm/Su/ribosomal P as well as anti-DNA/chromatin. In contrast, production of anti-DNA/chromatin Abs was associated with IL-6 overproduction in pristane-treated mice, but not in lpr mice. The data strongly support the idea that different subsets of autoantibodies are regulated differentially by cytokine stimulation and/or Fas signaling.

Induction of hypergammaglobulinemia and macrophage activation by silicone gels and oils in female A.SW mice

Although most published epidemiological studies have found little evidence of systemic autoimmune disease associated with silicone breast implants, there still remains a question of whether silicones can cause local and/or systemic immune dysfunction. This study further investigates the effects of silicones on autoantibody and immunoglobulin production and macrophage activation in female A.SW mice. Sixty mice were divided among four treatment groups receiving a 0.5-ml intraperitoneal injection of either phosphate-buffered saline (PBS), pristane, silicone gel, or silicone oil. Test bleeds were taken periodically for 6 months. In contrast to pristane, neither silicone gel nor silicone oil induced lupus-associated antinuclear autoantibodies (immunoglobulin G [IgG] anti-nRNP/Sm, Su, and ribosomal P) or lupus nephritis. However, serum IgM became elevated persistently within 1 month of silicone gel or silicone oil administration. Also, the level of IgG3 was clearly elevated in silicone oil-treated mice. In contrast, IgG1, IgG2a, and IgG2b levels were not affected greatly by either silicone gel or oil. Furthermore, peritoneal macrophages from silicone- and pristane-treated mice produced higher levels of interleukin-1beta (IL-1beta) and IL-6 than those from PBS-treated mice after lipopolysaccharide stimulation. These results suggest that silicone gels and oils are capable of inducing hypergammaglobulinemia and activating macrophages in female A.SW mice.