Autoreactive Antibodies Research Articles

Systemic Lupus Erythematosus: Pathogenesis at the Functional Limit of Redox Homeostasis

Systemic lupus erythematosus (SLE) is a disease characterized by the production of autoreactive antibodies and cytokines, which are thought to have a major role in disease activity and progression. Immune system exposure to excessive amounts of autoantigens that are not efficiently removed is reported to play a significant role in the generation of autoantibodies and the pathogenesis of SLE. While several mechanisms of cell death-based autoantigenic exposure and compromised autoantigen removal have been described in relation to disease onset, a significant association with the development of SLE can be attributed to increased apoptosis and impaired phagocytosis of apoptotic cells. Both apoptosis and impaired phagocytosis can be caused by hydrogen peroxide whose cellular production is enhanced by exposure to endogenous hormones or environmental chemicals, which have been implicated in the pathogenesis of SLE. Hydrogen peroxide can cause lymphocyte apoptosis and glutathione depletion, both of which are associated with the severity of SLE. The cellular accumulation of hydrogen peroxide is facilitated by the myriad of stimuli causing increased cellular bioenergetic activity that enhances metabolic production of this toxic oxidizing agent such as emotional stress and infection, which are recognized SLE exacerbating factors. When combined with impaired cellular hydrogen peroxide removal caused by xenobiotics and genetically compromised hydrogen peroxide elimination due to enzymatic polymorphic variation, a mechanism for cellular accumulation of hydrogen peroxide emerges, leading to hydrogen peroxide-induced apoptosis and impaired phagocytosis, enhanced autoantigen exposure, formation of autoantibodies, and development of SLE.

Synergistic effect of IgG4 antibody and CTLs causes tissue inflammation in IgG4-related disease.

IgG4-related disease (IgG4-RD) is characterized by multi-organ irreversible damage resulting from tissue-specific infiltration of IgG4+ plasma cells and cytotoxic T lymphocytes (CTLs). However, whether IgG4 antibody contributes to the inflammation remains unclear. In this study, we established a mouse model that enabled us to evaluate the pathogenic function of IgG4 antibodies in response to a tissue-specific autoantigen using recombinant ovalbumin (OVA)-specific human IgG4 monoclonal antibody (rOVA-hIgG4 mAb) and the mice expressing OVA of the pancreatic islets (RIP-mOVA mice). We found no inflammatory effect of rOVA-hIgG4 mAb transfer alone; however, co-transfer with OVA-specific CD8 CTLs (OT-I T cells) induced tissue damage with dense lymphocytic inflammation in the pancreas of RIP-mOVA mice. rOVA-hIgG4 mAb caused accumulation of conventional DC1 cells (cDC1s) in the lymphoid tissues, and the dendritic cells (DCs) activated the OT-I T cells via cross-presentation. We also revealed that the synergistic effects of CTLs and antibodies were observed in the other subclasses including endogenous antibodies if they recognized the same antigen. The transfer of OVA-specific CD4 helper T cells (OT-II T cells) into RIP-mOVA mice induced the production of anti-OVA antibody, which had a synergistic effect, through acquisition of a T follicular helper (TFH) phenotype. Moreover, using OT-II T cells deficient in Bcl6 caused lower anti-OVA antibody production and inflammation with OT-I T cells. Our results indicated that autoreactive IgG4 antibodies play an important role of the tissue-specific CTL response in IgG4-RD.

Human red blood cell stroma: an alternative to traditional allogeneic adsorption methods.

Allogeneic adsorption (alloadsorption) involves incubating an aliquot of patient plasma with red blood cells (RBCs) of a known phenotype to facilitate removal of autoantibodies and allow for detection of remaining, potentially clinically significant alloantibodies. Alloadsorptions are routinely performed using fresh or frozen donor RBCs having particular Rh and Kidd phenotypes, and are usually enzyme or ZZAP treated before adsorptions. RBC stroma would provide a method to prepare large amounts of adsorption material that may be stored frozen and used when needed. A total of 309 samples were presented to our institutions (American Red Cross, Southwest Region Texas laboratories) with serologic positive IgG autoantibodies, had allogeneic RBC stromal adsorptions performed, and underlying alloantibodies identified. After papain treatment of RBCs from group O, K- individuals who were R1 R1 , R2 R2 , and rr where at least one individual was Jk(a+b-) and one individual Jk(a-b+), stroma was prepared using digitonin digestion of the RBC membrane. Large amounts of stroma could be obtained and were aliquoted and frozen at -18°C or less for up to 2 years. One hundred seventeen of 309 (38%) samples demonstrated alloantibodies following stromal alloadsorptions. Twenty-two different alloantibodies were identified in the stroma-adsorbed plasma, with an average of two stromal adsorptions resolving the autoantibody reactivity. The specificities of alloantibodies underlying the autoantibody included those in the Rh system (112), Kell system (24), Duffy system (14), Kidd system (30), MNS system (19), Lutheran system (2), and Diego system (2). Successful removal of autoantibody using RBC stromal adsorption was obtained in 308 samples and allowed for the identification of underlying alloantibodies in 117 samples. Preparation and use of RBC stroma should significantly benefit immunohematology reference laboratories in their antibody investigations.

Immune-Monitoring Disease Activity in Primary Membranous Nephropathy.

Primary membranous nephropathy (MN) is a glomerular disease mediated by autoreactive antibodies, being the main cause of nephrotic syndrome among adult patients. While the pathogenesis of MN is still controversial, the detection of autoantibodies against two specific glomerular antigens, phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain containing 7A (THSD7A), together with the beneficial effect of therapies targeting B cells, have highlighted the main role of autoreactive B cells driving this renal disease. In fact, the detection of PLA2R-specific IgG4 antibodies has resulted in a paradigm shift regarding the diagnosis as well as a better prediction of the progression and recurrence of primary MN. Nevertheless, some patients do not show remission of the nephrotic syndrome or do rapidly recur after immunosuppression withdrawal, regardless the absence of detectable anti-PLA2R antibodies, thus highlighting the need of other immune biomarkers for MN risk-stratification. Notably, the exclusive evaluation of circulating antibodies may significantly underestimate the magnitude of the global humoral memory immune response since it may exclude the role of antigen-specific memory B cells. Therefore, the assessment of PLA2R-specific B-cell immune responses using novel technologies in a functional manner may provide novel insight on the pathogenic mechanisms of B cells triggering MN as well as refine current immune-risk stratification solely based on circulating autoantibodies.

Role of Heat Shock Proteins in Glaucoma.

Glaucoma, one of the most common causes of blindness worldwide, is a multifactorial neurodegenerative disease characterized by damage of retinal ganglion cells and optic nerve degeneration. However, the exact mechanism leading to glaucoma is still not understood. Evidences suggest an immunological involvement in the pathogenesis. Among other immune responses, altered autoantibody patterns were found in glaucoma patients. Especially elevated antibody levels against heat shock proteins (HSPs), like HSP27 or HSP60, were identified. In an animal model, an immunization with these HSPs induced a pressure-independent retinal ganglion cell degeneration and axon loss, hence mimicking glaucoma-like damage. In addition, development of autoreactive antibodies, as well as a glia and T-cell activation, were described in these animals. Recently, we noted that intravitreal HSP27 injection likewise led to a degeneration of retinal ganglion cells and their axons. Therefore, HSP27 might have a direct damaging effect on retinal cells, and might play a key role in glaucoma.

Very late-onset recurrent myelitis in a patient diagnosed with antiphospholipid syndrome: A puzzle of autoimmunity

We describe the case of a man with a very-late onset neuromyelitis optica spectrum disorder syndrome (NMOSD) who was initially diagnosed as recurrent antiphospholipid syndrome-associated myelitis. This case illustrates that a puzzle of autoreactive antibodies can be detected in patients having neurological syndromes belonging to the NMOSD. Prompt identification and timely immunosuppression prevent relapses and the accumulation of irreversible disability.

Review: Pathogenesis of Helicobacter pylori infection.

In this review, we shall focus on the last year progression understanding the pathogenesis of Helicobacter pylori infection in the light of recent data related to adaptation of H pylori to the harsh acidic environment in the stomach, colonization of gastric mucosa via interaction with mucin 5 (MUC5AC) and other host cell receptors, the ability to form biofilm, interference with the host metabolic pathways, and induction of neuroimmune cross‐talk as well as downregulation of gastric barrier homeostasis and its consequences for the disease development. The role of the membrane vesicles of these bacteria has been emphasized as an important source of virulence factors. Furthermore, we shall describe molecular and functional studies on new aspects of VacA and CagA virulence, including the role of urease in the upregulation of VacA toxicity, an epithelial‐mesenchymal transition mediated by CagA, and the role of interaction of HopQ adhesin with carcinoembryonic antigen‐related cell adhesion molecules (CEACAMs) in CagA translocation into the host cells by the type IV secretion system (T4SS). The role of molecular mimicry between a common sequence (ATVLA) of H pylori heat shock protein (Hsp) B and human Hsp60 in the induction of potentially autoreactive antibodies is discussed. All these new data illustrate further progress in understanding H pylori pathogenicity and facilitate the search for new therapeutic targets as well as development of immunoprophylaxis methods based on new chimeric UreB and HpA proteins.

Expression of human endogenous retroviruses in pemphigus vulgaris patients.

Pemphigus is a severe, potentially life-threatening autoimmune blistering mucocutaneous disease which establishes with autoreactive IgG antibodies that target cellular adhesions, precisely extracellular domains of keratinocyte proteins. Several genetic and environmental elements are believed to contribute to the pathogenesis of the disease. The extent to whichthe initiation and progress of this autoimmune blistering disease may be influenced by the expression of human endogenous retroviruses (HERVs) remains to be elucidated. In this study, we evaluated the expression of HERV groups (K, W, and H) in pemphigus vulgaris (PV) patients in comparison to controls. Peripheral blood samples were collected from 24 PV patients and the corresponding age- and sex-matched healthy controls to extract total RNA for evaluation of HERV-K (HML-2), HERV-W, and HERV-H, env gene expression profile by qPCR. The mRNA expression level of HERV-K, HERV-W, and HERV-H were significantly upregulated in PV patients in comparison to healthy controls (P < 0.0001). The difference in expression of studied HERVs groups between men and women was no significant (P > 0.05). Although rituximab taking patients had a decreased expression level of studied HERVs, the results were not significant (P > 0.05). According to our obtained data, HERVs expression could be measured as a possible diagnostic tool for detection of PV and monitoring of the treatment.

Correlation of Parasite Burden, kDNA Integration, Autoreactive Antibodies, and Cytokine Pattern in the Pathophysiology of Chagas Disease.

Chagas disease (CD), caused by the protozoan Trypanosoma cruzi (T. cruzi), is the main parasitic disease in the Western Hemisphere. Unfortunately, its physiopathology is not completely understood, and cardiomegaly development is hard to predict. Trying to explain tissue lesion and the fact that only a percentage of the infected individuals develops clinical manifestations, a variety of mechanisms have been suggested as the provokers of CD, such as parasite persistence and autoimmune responses. However, holistic analysis of how parasite and host-related elements may connect to each other and influence clinical outcome is still scarce in the literature. Here, we investigated murine models of CD caused by three different pathogen strains: Colombian, CL Brener and Y strains, and employed parasitological and immunological tests to determine parasite load, antibody reactivity, and cytokine production during the acute and chronic phases of the disease. Also, we developed a quantitative PCR (qPCR) protocol to quantify T. cruzi kDNA minicircle integration into the mammalian host genome. Finally, we used a correlation analysis to interconnect parasite- and host-related factors over time. Higher parasite load in the heart and in the intestine was significantly associated with IgG raised against host cardiac proteins. Also, increased heart and bone marrow parasitism was associated with a more intense leukocyte infiltration. kDNA integration rates correlated to the levels of IgG antibodies reactive to host cardiac proteins and interferon production, both influencing tissue inflammation. In conclusion, our results shed light into how inflammatory process associates with parasite load, kDNA transfer to the host, autoreactive autoantibody production and cytokine profile. Altogether, our data support the proposal of an updated integrative theory regarding CD pathophysiology.

Response to comment on 'AIRE-deficient patients harbor unique high-affinity disease-ameliorating autoantibodies'.

In 2016, we reported four substantial observations of APECED/APS1 patients, who are deficient in AIRE, a major regulator of central T cell tolerance (Meyer et al., 2016). Two of those observations have been challenged. Specifically, 'private' autoantibody reactivities shared by only a few patients but collectively targeting >1000 autoantigens have been attributed to false positives (Landegren, 2019). While acknowledging this risk, our study-design included follow-up validation, permitting us to adopt statistical approaches to also limit false negatives. Importantly, many such private specificities have now been validated by multiple, independent means including the autoantibodies' molecular cloning and expression. Second, a significant correlation of antibody-mediated IFNα neutralization with an absence of disease in patients highly disposed to Type I diabetes has been challenged because of a claimed failure to replicate our findings (Landegren, 2019). However, flaws in design and implementation invalidate this challenge. Thus, our results present robust, insightful, independently validated depictions of APECED/APS1, that have spawned productive follow-up studies.

Emphysema-associated Autoreactive Antibodies Exacerbate Post-Lung Transplant Ischemia-Reperfusion Injury.

Chronic obstructive pulmonary disease-associated chronic inflammation has been shown to lead to an autoimmune phenotype characterized in part by the presence of lung autoreactive antibodies. We hypothesized that ischemia-reperfusion injury (IRI) liberates epitopes that would facilitate preexisting autoantibody binding, thereby exacerbating lung injury after transplant. We induced emphysema in C57BL/6 mice through 6 months of cigarette smoke (CS) exposure. Mice with CS exposure had significantly elevated serum autoantibodies compared with non-smoke-exposed age-matched (NS) mice. To determine the impact of a full preexisting autoantibody repertoire on IRI, we transplanted BALB/c donor lungs into NS or CS recipients and analyzed grafts 48 hours after transplant. CS recipients had significantly increased lung injury and immune cell infiltration after transplant. Immunofluorescence staining revealed increased IgM, IgG, and C3d deposition in CS recipients. To exclude confounding alloreactivity and confirm the role of preexisting autoantibodies in IRI, syngeneic Rag1-/- (recombination-activating protein 1-knockout) transplants were performed in which recipients were reconstituted with pooled serum from CS or NS mice. Serum from CS-exposed mice significantly increased IRI compared with control mice, with trends in antibody and C3d deposition similar to those seen in allografts. These data demonstrate that pretransplant CS exposure is associated with increased IgM/IgG autoantibodies, which, upon transplant, bind to the donor lung, activate complement, and exacerbate post-transplant IRI.

161-OR: Autoantibodies Directed to Deamidated Post-translationally Modified IA-2 Epitopes in Type 1 Diabetes

Autoimmune disorders such rheumatoid arthritis (RA) harbor autoantibodies against a variety of post-translationally modified (PTM) proteins. We aimed to investigate whether PTM epitopes of IA-2, a major autoantigen related to type 1 diabetes (T1D), are targeted by autoantibody responses. The extracellular domain of IA-2 (IA-2-ec) was synthesized incorporating deamidated amino acid residues (IA-2ec-PTM) previously found to elicit T cell responses in T1D patients. IA-2ec-PTM was then subjected to immunoprecipitation with sera from T1D patients. Notably, autoantibody reactivity towards IA-2ec-PTM was present in 28% of T1D patients as compared to ~9% of serum reactivity against the native IA-2ec. The area under the ROC curve (ROC AUC) of IA-2ec-PTM autoantibodies revealed that these autoantibodies can adequately distinguish between T1D patient and control groups (ROC AUC: 0.7132; P &amp;lt; 0.0001). Relatives of T1D probands (from the TrialNet Pathway to Prevention Study) carrying both IA-2ec-PTM AAb and the high-risk HLA-DRB1*04-DQB1*03:02 haplotype progressed rapidly to onset of T1D (Stage 3) compared to those relatives who did not carry these immunologic abnormalities (P = 0.003). Understanding the mechanisms underlying PTMs of islet autoantigens, such as IA-2ec-PTM, is critical to develop new research to determine the ability of modified epitopes to induce islet autoimmunity, their potential role as biomarkers of islet cell injury as well as breaking immune tolerance to islet cell antigens through neo-antigen formation. Disclosure M.J. Acevedo-Calado: None. S. Pietropaolo: None. L. Yu: None. A.W. Michels: Stock/Shareholder; Self; IM Therapeutics. M. Pietropaolo: None. Funding National Institutes of Health

Preferential Reactivity of Dipeptidyl Peptidase-IV Inhibitor-Associated Bullous Pemphigoid Autoantibodies to the Processed Extracellular Domains of BP180.

Bullous pemphigoid (BP) is a common autoimmune blistering disease in which autoantibodies target the hemidesmosomal components BP180 and/or BP230 in basal keratinocytes. In BP, 80 to 90% of autoantibodies target the juxtamembranous extracellular non-collagenous 16th A (NC16A) domain of BP180. Recently, the administration of dipeptidyl peptidase-IV inhibitors (DPP4i), which are widely used as antihyperglycemic drugs, has been recognized to be a causative factor for BP. DPP4i-associated BP (DPP4i-BP) autoantibodies tend to target epitopes on non-NC16A regions of BP180, and the pathomechanism for the development of the unique autoantibodies remains unknown. To address the characteristics of DPP4i-BP autoantibodies in detail, we performed epitope analysis of 18 DPP4i-BP autoantibodies targeting the non-NC16A domains of BP180 using various domain-specific as well as plasmin-digested polypeptides derived from recombinant BP180. Firstly, Western blotting showed that only one DPP4i-BP serum reacted with the epitopes on the intracellular domain of BP180, and no sera reacted with the C-terminal domain of the molecule. In addition, only 2 DPP4i-BP sera reacted with BP230 as determined by enzyme-linked immunosorbent assay. Thus, DPP4i-BP autoantibodies were found to mainly target the non-NC16A mid-portion of the extracellular domain of BP. Interestingly, Western blotting using plasmin-digested BP180 as a substrate revealed that all of the DPP4i-BP sera reacted more intensively with the 97-kDa processed extracellular domain of BP180, which is known as the LABD97 autoantigen, than full-length BP180 did. All of the DPP4i-BP autoantibodies targeting the LABD97 autoantigen were IgG1, and IgG4 was observed to react with the molecule in only 7 cases (38.9%). In summary, the present study suggests that IgG1-class autoantibodies targeting epitopes on the processed extracellular domain of BP180, i.e., LABD97, are the major autoantibodies in DPP4i-BP.

Autoreactive T-Lymphocytes in Inflammatory Skin Diseases.

The presence of one or several autoantigen(s) and a response by the adaptive immune system are the key criteria to classify a pathology as an autoimmune disease. The list of entities fulfilling this criterion is currently growing in the light of recent advancements in the pathogenetic understanding of a number of important dermatoses. The role of autoreactive T-lymphocytes differs amongst these pathologies. While they are directly involved as effector cells attacking and sometimes killing their respective target in some diseases (e.g., vitiligo), they provide help to B-lymphocytes, which in turn produce the pathogenic autoreactive antibodies in others (pemphigus and pemphigoid). Atopic dermatits is a chimera in this regard, as there is evidence for both functions. Psoriasis is an example for an entity where autoantigens were finally identified, suggesting that at least a subgroup of patients should be classified as suffering from a true autoimmune rather than autoinflammatory condition. Identification of resident memory T-lymphocytes (TRM) helped to understand why certain diseases relapse at the same site after seemingly effective therapy. Therefore, the in-depth characterization of autoreactive T-lyphocytes goes way beyond an academic exercise and opens the door toward improved therapies yielding durable responses. TRM are particularly suitable targets in this regard, and the clinical efficacy of some established and emerging therapeutic strategies such as the inhibition of Janus Kinase 3 or interleukin 15 may rely on their capacity to prevent TRM differentiation and maintenance. Research in this field brings us closer to the ultimate goal in the management of autoimmunity at large, namely resetting the immune system in order to restore the state of tolerance.

Plasma proteomic and autoantibody profiles reveal the proteomic characteristics involved in longevity families in Bama, China

BackgroundChinese Bama Yao Autonomous County is a well-known longevity region in the world. In the past 30 years, population and genome studies were undertaken to investigate the secret of longevity and showed that longevity is the result of a combination of multiple factors, such as genetic, environmental and other causes. In this study, characteristics of the blood plasma proteomic and autoantibody profiles of people from Bama longevity family were investigated.MethodsSixty-six plasma donors from Chinese Bama longevity area were recruited in this study. Thirty-three offsprings of longevous families were selected as case studies (Longevous group) and 33 ABO (blood type), age, and gender-matched subjects from non-longevous families were selected as controls (Normal group). Each group contains 3 biological replicates. Tandem mass tag-based proteomic technique was used to investigate the differentially expressed plasma proteins between the two groups. The auto-reactive IgG antibody profiles of the 3 pooled samples in each group were revealed by human proteome microarrays with 17,000 recombinant human proteins.ResultsFirstly, 525 plasma proteins were quantified and 12 proteins were discovered differentially expressed between the two groups. Secondly, more than 500 proteins were recognized by plasma antibodies, 14 proteins ware differentially reacted with the autoantibodies in the two groups. Bioinformatics analysis showed some of the differential proteins and targeted autoantigens were involved in cancer, cardiovascular disease and immunity.ConclusionsProteomic and autoantibody profiles varied between the offspring of longevous and normal families which are from the same area and shared the same environmental factors. The identified differences were reported to be involved in several physiological and pathological pathways. The identified proteins will contribute to a better understanding of the proteomic characteristics of people from Bama longevous area and a revelation of the molecular mechanisms of longevity.

Safety and Tolerability of Omalizumab: A Randomized Clinical Trial of Humanized Anti-IgE Monoclonal Antibody in Systemic Lupus Erythematosus.

Autoreactive IgE antibodies have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). We hypothesize that omalizumab, a monoclonal antibody binding IgE, may improve SLE activity by reducing type I interferon (IFN) production by hampering plasmacytoid dendritic cells and basophil activation. This study was undertaken to assess the safety, tolerability, and clinical efficacy of omalizumab in mild to moderate SLE. Sixteen subjects with SLE and a Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score of ≥4 and elevated autoreactive IgE antibody levels were randomized to receive omalizumab or placebo (2:1) for 16 weeks, followed by 16 weeks of open-label treatment and a 4-week washout period. The SLEDAI-2K score, British Isles Lupus Assessment Group index (BILAG 2004) score, and physician's global assessment of disease activity were recorded at each visit. The type I IFN-induced gene signature was determined using quantitative polymerase chain reaction. Omalizumab was well tolerated with no allergic reactions, and mostly mild adverse events comparable to those experienced with placebo treatment. SLEDAI-2K scores improved in the omalizumab group compared to the placebo group at week 16 (P = 0.038), as well as during the open-label phase in subjects initially receiving placebo (P = 0.02). No worsening in BILAG scores or the physician's global assessment was detected. There was a trend toward a reduction in IFN gene signature in subjects treated with omalizumab (P = 0.11), especially in subjects with a high baseline IFN signature (P = 0.052). Our findings indicate that omalizumab is well tolerated in SLE and is associated with improvement in disease activity. Larger randomized clinical trials will be needed to assess the efficacy of omalizumab in patients with SLE.

Autoreactive potential of universal influenza vaccines

Abstract A universal influenza vaccine could save millions of lives in the event of a deadly pandemic. It is not clear why antibodies specific for conserved regions of influenza viruses are so rare. One possibility is that these antibodies have a higher potential to cross-react to self-proteins, and therefore B cells that generate these antibodies are deleted through tolerance mechanisms. Therefore, we examined whether cross-reactive influenza antibodies had a higher potential to be autoreactive than antibodies specific for one subtype of influenza. We previously demonstrated that H3N2-vaccinated mice treated with a low dose of rapamycin had more cross-reactive influenza antibodies and were better protected against subsequent lethal infections of multiple subtypes. Thus, we utilized rapamycin to increase the frequency of influenza cross-reactive antibodies, and tested whether these antibodies were more reactive to self-proteins than strain-specific antibodies. We found that mice with increased levels of cross-reactive influenza antibodies also had more IgM antibodies specific for self-antigens. Although the increase in autoreactive IgM antibodies was transient, it correlated with increased susceptibility to disease in mouse models of multiple sclerosis and Guillian-Barre Syndrome. Together, our results suggest that influenza cross-reactive antibodies have the potential to be autoreactive. These data have important implications for developing universal influenza vaccines designed to generate durable influenza cross-reactive antibodies.

A rationally engineered DNase1-Fc fusion protein ameliorates autoimmune glomerulonephritis

Abstract Loss of B cell tolerance and generation of autoreactive anti-nuclear antibodies are hallmarks of systemic lupus erythematosus and lupus nephritis. The mechanism of anti-nuclear immunoglobulin accumulation and clearance in lupus nephritis pathogenesis remains largely uncharacterized. Here, we show that innate immune activation in the NZB/W F1 mouse model and human lupus nephritis biopsies rapidly reduces expression of DNase1 (also called DNase I) in renal cortex proximal tubular cells. Unexpectedly, kidney DNase1 levels were no longer affected by TLR ligand agonism upon depletion of macrophages, indicating that local macrophage activation is required for the downmodulation of DNase1 in kidney epithelial cells. To overcome the loss of endogenous DNase1, we rationally designed a hyperactive actin-resistant variant of DNase1 with improved catalytic activity and acceptable in vivo pharmacokinetics. The engineered DNase1-Fc fusion protein ameliorates nephritis in a murine model of lupus and reduces immune complex deposition/complement fixation. Our data suggest that the loss of renal DNase1 through TLR signaling or other innate immune activation impairs clearance of autoreactive anti-nuclear immune complex deposits in the kidney to promote nephritis progression. While autoantibodies and autoreactive B cell activation are central to lupus pathogenesis, we hypothesize that renal cortical epithelial cells expressing high levels of DNase1 serve as gatekeepers to prevent detrimental nuclear immune complex deposition. Our findings provide a therapeutic rationale for using an engineered hyperactive actin-resistant DNase1-Fc for lupus nephritis.

Ikaros mutations can bypass the requirement for second co-stimulatory signal and lead to break of B-cell tolerance

Abstract Autoimmunity is thought to arise due to a combination of genetic and environmental factors. IKZF1, encoding the Zinc finger (ZnF) transcription factor Ikaros, is implicated in human autoimmunity through GWAS and recent discovery of germline IKZF1 mutations in patients with autoimmune diseases. We have previously created mouse models with targeted deletions of Ikaros DNA-binding ZnF1 or ZnF4, and recently found that mice lacking Ikaros ZnF4 (Ik-dF4) displayed very high levels of autoreactive antibodies and elevated levels of the autoimmunity-associated cytokine IL-6 in serum at young age, while mice lacking ZnF1 did not. Furthermore, ex vivo stimulation of peripheral B cells with anti-IgM (aIgM) +/− CD40L revealed that Ik-dF4 B cells responded to BCR-stimulation alone (aIgM), while wt B cells required a second co-stimulatory signal (CD40L). To understand the underlying mechanism, we performed transcriptome profiling of these stimulated wt and Ik-dF4 B cells. Overall, the Ik-dF4 B cells displayed the same pattern of gene-expression changes as wt B cell upon activation by both signals (aIgM + CD40L). Further analysis revealed a set of genes selectively altered upon aIgM alone in Ik-dF4 B cells, and another set of genes that were aberrantly expressed in Ik-dF4 B cells at baseline. Pathway analysis suggest candidate mediators, and we have initiated functional studies. Preliminary results indicate that a small molecule inhibitor can block the aberrant activation with aIgM alone in Ik-dF4 B cells, while displaying only partial inhibition of the normal two-signal activation. Studies are actively ongoing to confirm these preliminary findings, and we will present our results to date at the meeting for how Ikaros regulates B cell tolerance.

In the Right Place, at the Right Time: Spatiotemporal Conditions Determining Plasma Cell Survival and Function.

Plasma cells (PCs), the B lineage cells responsible for producing and secreting antibodies (Abs), are critical cellular components of the humoral immune system. While most of the antibody-secreting cells in the body have a rather short lifetime of a few days, some of them can become long-lived and persist in the body over the entire life span of an individual. The majority of these long-lived plasma cells secretes protective antibodies against pathogens, and are thereby crucial for the humoral component of immunological memory. The generation of these protective antibody-secreting cells can be triggered by an exposure to pathogens, and also by vaccination. Although the majority of plasma cells are protective, sometimes long-lived plasma cells produce autoreactive antibodies, which contribute to the pathogenesis and perpetuation of chronic autoimmune diseases, including lupus erythematosus, rheumatoid arthritis, or multiple sclerosis. In order to promote the formation of protective antibody-secreting cells and to target pathogenic plasma cells, it is crucial to understand the signals which promote their longevity and allow them to exert their function. In recent years, it has become clear that plasma cells depend on extrinsic factors for their survival, leading to the concept that certain tissue microenvironments promote plasma cell retention and longevity. However, these niches are not static structures, but also have dynamic features with respect to their cellular composition. Here, we review what is known about the molecular and cellular composition of the niches, and discuss the impact of dynamic changes within these microenvironments on plasma cell function. As plasma cell metabolism is tightly linked to their function, we present new tools, which will allow us to analyze metabolic parameters in the plasma cell niches in vivo over time.