Production Of Pathogenic Autoantibodies Research Articles

IL-23 inhibits autoimmunity by facilitating clearance of apoptotic bodies in the marginal zone (171.26)

Abstract IL-23 helps expansion of Th17 cells which are important in the pathogenesis of spontaneous autoimmune disease in BXD2 mice. In this study, we surprisingly found that IL-23p19-deficient BXD2 mice (BXD2-Il23-/-) exhibit accelerated development of spontaneous germinal centers (GCs) and production of pathogenic autoantibodies, compared with wild-type BXD2 mice. Expression of IL-23 by adenovirus in BXD2-Il23-/- mice reversed these phenotypes. IL-23R was mainly expressed by marginal zone macrophages (MZMs) in the spleen of mice, as indicated by the GFP-IL-23R reporter. In BXD2-Il23-/-, however, there was an age-related loss of both MZMs and CD21hiIgMhi marginal zone (MZ) B cells. MZMs are a small subset of specialized splenic macrophages essential for clearance of apoptotic cells entering to the spleen from circulation to prevent generation of immunogenic autoantigens. MZM specific depletion by clondronate liposome severely accelerated BXD2 autoimmune disease progression. Absence of IL-23 correlates with downregulated expression of BAFF by MZMs which is essential for the differentiation of MZ B cells. Our results suggest a unique mechanism for IL-23 to limit autoimmunity in that IL-23 supports the cross-talk between MZM and MZ B cells. In this model, IL-23 acts on MZM to upregulate BAFF to promote the survival of MZ B cells, and MZ B cells help to maintain the survival of MZM. Loss of MZM is associated with defective clearance of apoptotic cells and acceleration of autoimmunity.

Follicular helper T cells in immunity and systemic autoimmunity

Follicular helper T (T(FH)) cells are essential for B-cell maturation and immunoglobulin production after immunization with thymus-dependent antigens. Nevertheless, the development and function of T(FH) cells have been less clearly defined than classic CD4(+) effector T-cell subsets, including T-helper-1 (T(H)1), T(H)2 and T(H)17 cells. As such, our understanding of the genesis of T(FH) cells in humans and their role in the development of autoimmunity remains incomplete. However, evidence from animal models of systemic lupus erythematosus (SLE) and patients with systemic autoimmune diseases suggests that these cells are necessary for pathogenic autoantibody production, in a manner analogous to their role in promotion of B-cell maturation during normal immune responses. In this Review, I discuss the findings that have increased our knowledge of T(FH)-cell development and function in normal and aberrant immune responses. Such information might improve our understanding of autoimmune diseases, such as SLE, and highlights the potential of T(FH) cells as therapeutic targets in these diseases.

Autoantibodies to estrogen receptor α interfere with T lymphocyte homeostasis and are associated with disease activity in systemic lupus erythematosus

Estrogens influence many physiologic processes and are also implicated in the development or progression of numerous diseases, including autoimmune disorders. Aberrations of lymphocyte homeostasis that lead to the production of multiple pathogenic autoantibodies, including autoantibodies specific to estrogen receptor (ER), have been detected in the peripheral blood of patients with systemic lupus erythematosus (SLE). This study was undertaken to assess the presence of both anti-ERα and anti-ERβ antibodies in sera from patients with SLE, to analyze the effect of these antibodies on peripheral blood T lymphocyte homeostasis, and to evaluate their role as determinants of disease pathogenesis and progression. Anti-ER antibody serum immunoreactivity was analyzed by enzyme-linked immunosorbent assay in samples from 86 patients with SLE and 95 healthy donors. Phenotypic and functional analyses were performed by flow cytometry and Western blotting. Anti-ERα antibodies were present in 45% of the patients with SLE, whereas anti-ERβ antibodies were undetectable. In healthy donors, anti-ERα antibodies induced cell activation and consequent apoptotic cell death in resting lymphocytes as well as proliferation of anti-CD3-stimulated T lymphocytes. A significant association between anti-ERα antibody values and clinical parameters, i.e., the SLE Disease Activity Index and arthritis, was found. Our data suggest that anti-ERα autoantibodies interfere with T lymphocyte homeostasis and are significantly associated with lupus disease activity.

Chronic urticaria and use of statins

To the Editor, I read with interest the consensus guidelines on chronic urticaria by Steven KW Chow and colleagues [1] but have reservations with the statement that angiotensin converting enzyme inhibitors (ACEIs) should usually be avoided in chronic urticaria with or without angioedema. Although the EAACI/GA2LEN/EDF/WAO position paper does allude to the fact that ACEIs come second to non-steroidal anti-inflammatory drugs in eliciting and aggravating urticaria [2], the level of evidence to support this statement was not provided. Yet another consensus statement on the management of urticaria by Godse KV et al. [3] does not mention ACEIs as a possible trigger for urticaria. The incidence of urticaria to the ACEI drug enalapril was reported at 0.3% (32 of 12,543 patients) in a 12 months post-marketing surveillance study, but the report also mentioned that this necessitated withdrawal of the drug only in 5 cases and 6 other cases of urticaria were not attributed to enalapril [4]. Dr. Pfeiffer [5] referenced the above paper in a correspondence to a review by Dr. Allen P Kaplan [6] on chronic urticaria and angioedema in The New England Journal of Medicine, but that ACEI drugs can elicit urticaria was not entirely accepted by Dr. Kaplan in his reply [5]. A more commonly prescribed class of drugs that have a higher incidence of urticaria are lipid lowering statins. Manufacturers of statin drugs report the combined incidence of rash and allergic reactions to be 7.7% (data on file; Parke-Davis, USA) that is much higher than that for ACEIs [see Table 1 for published reports; MEDLINE from PubMed, EMBASE, BNI, CINAHL with search terms: 'statin', 'urticaria']. A recently published 10-year study from the French PharmacoVigilance Database reported 7.3% of systemic lupus erythematosus cases associated with statin use [with reporting odds ratio at 1.67 (95% CI 1.02-2.74)] [7]. The mechanisms of statin-induced (autoimmune) urticaria/systemic lupus erythematosus may be related to (1) the proapoptotic nature of the drug (at least the second generation statins) that may release otherwise unaccessible nuclear antigens and subsequent generation of autoantibodies; and (2) statins have been shown to promote a shift from T helper 1 (Th1) to Th2 immune responses that leads to B-cell reactivity and the production of pathogenic autoantibodies [8-10]. Table 1 Reports of statin use with development of urticaria With several consensus guidelines from various clinical groups recommending prophylactic statin therapy, clinicians should be aware of all side effects with these widely prescribed medications.

Asbestos activates CH12.LX B-lymphocytes via macrophage signaling

The impact of asbestos exposure on the development and progression of autoimmunity is becoming increasingly recognized as a public health issue. Epidemiological studies have shown an association between exposure to airborne silicates, such as asbestos, and autoimmunity, but the etiology remains unresolved. B1a B-lymphocytes have been implicated in autoimmune responses in mice, and splenic B1a cell numbers are altered following asbestos exposure. The purpose of this study was to explore the possible role of B1a B-lymphocytes in the production of pathogenic autoantibodies by testing the hypothesis that B1a B-lymphocytes directly react with asbestos and increase production of antibodies. The B1a-like B-lymphocyte model, CH12.LX, was exposed to asbestos in vitro via direct and indirect mechanisms. The effect was determined of these exposures on the rate of proliferation and on production of various immunoglobulin classes. Direct exposure elicited no measurable response by the CH12.LX cells. Culturing the CH12.LX cells in media from asbestos-exposed RAW 264.7 macrophages, however, decreased the proliferation rate and stimulated the cells to increase production of the immunoglobulin isotypes IgG1, IgG3, and IgA. It was discovered that asbestos stimulated the macrophages to increase production of the cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α. Recombinant murine IL-6 caused similar results seen with the macrophage media, indicating a role of IL-6 in stimulating a response by the B1a B-lymphocytes to asbestos. In correlation with the in vitro data, it was determined ex vivo that exposure of peritoneal cells (from C57Bl/6 mice) to asbestos caused an increase in the expression of IL-6 and TNFα, as well as of surface expression of IgA on the peritoneal B1a B-lymphocytes. These data demonstrate that asbestos leads to immunologic changes consistent with activation of B1a B-lymphocytes. This study also provides a model for analyzing the critical steps that may be involved in asbestos-induced autoimmune responses.

Noncollagenous 16A domain of type XVII collagen-reactive CD4+ T cells play a pivotal role in the development of active disease in experimental bullous pemphigoid model

Bullous pemphigoid (BP), the most common autoimmune blistering disease, is caused by autoantibodies against type XVII collagen (COL17). We recently demonstrated that CD4+ T cells were crucial for the production of anti-COL17 IgG and for the development of the BP phenotype by using a novel active BP mouse model by adoptively transferring immunized splenocytes into immunodeficient COL17-humanized mice. Noncollagenous 16A (NC16A) domain of COL17 is considered to contain the main pathogenic epitopes of BP, however, the pathogenicity of COL17 NC16A-reactive CD4+ T cells has never been elucidated. To address this issue, we modulated the immune responses against COL17 in active BP model by using anti-CD40 ligand (CD40L) monoclonal antibody MR1, an inhibitor of the CD40-CD40L interaction, in various ways. First, we show the essential role of CD4+ T cells in the model by showing that CD4+ T cells isolated from wild-type mice immunized with human COL17 enabled naïve B cells to produce anti-COL17 NC16A IgG in vivo. Second, we show that the activation of anti-COL17 NC16A IgG-producing B cells via CD40-CD40L interaction was completed within 5 days after the adoptive transfer of immunized splenocytes. Notably, a single administration of MR1 at day 0 was enough to inhibit the production of anti-COL17 NC16A IgG and to diminish skin lesions despite the presence of restored anti-COL17 IgG at the later stage. In contrast, the delayed administration of MR1 failed to inhibit the production of anti-COL17 NC16A IgG and the development of the BP phenotype. These results strongly suggest that COL17 NC16A-reactive CD4+ T cells play a pivotal role in the production of pathogenic autoantibodies and in the development of active disease in experimental BP model.

Emerging Roles for the Interferon-Inducible p200-Family Proteins in Sex Bias in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease involving multiple organs. The disease is characterized by the production of pathogenic autoantibodies to DNA and certain nuclear antigens, chronic inflammation, and immune dysregulation. Genetic studies involving SLE patients and mouse models have indicated that multiple lupus susceptible genes contribute to the disease phenotype. Notably, the development of SLE in patients and in certain mouse models exhibits a strong sex bias. In addition, several lines of evidence indicates that activation of interferon-α (IFN-α) signaling in immune cells and alterations in the expression of certain immunomodulatory cytokines contribute to lupus pathogenesis. Studies have implicated factors, such as the X chromosomal gene dosage effect and the sex hormones, in gender bias in SLE. However, the molecular mechanisms remain unclear. Additionally, it remains unclear whether these factors influence the "IFN-signature," which is associated with SLE. In this regard, a mutually positive regulatory feedback loop between IFNs and estrogen receptor-α (ERα) has been identified in immune cells. Moreover, studies indicate that the expression of certain IFN-inducible p200-family proteins that act as innate immune sensors for cytosolic DNA is differentially regulated by sex hormones. In this review, we discuss how the modulation of the expression of the p200-family proteins in immune cells by sex hormones and IFNs contributes to sex bias in SLE. An improved understanding of the regulation and roles of the p200-family proteins in immune cells is critical to understand lupus pathogenesis as well as response (or the lack of it) to various therapies.

B Cell Maturation Antigen Deficiency Exacerbates Lymphoproliferation and Autoimmunity in Murine Lupus

Systemic lupus erythematosus and its preclinical lupus-prone mouse models are autoimmune disorders involving the production of pathogenic autoantibodies. Genetic predisposition to systemic lupus erythematosus results in B cell hyperactivity, survival of self-reactive B cells, and differentiation to autoantibody-secreting plasma cells (PCs). These corrupt B cell responses are, in part, controlled by excess levels of the cytokine BAFF that normally maintains B cell homeostasis and self-tolerance through limited production. B cell maturation Ag (BCMA) is a receptor for BAFF that, under nonautoimmune conditions, is important for sustaining enduring Ab protection by mediating survival of long-lived PCs but is not required for B cell maturation and homeostasis. Through analysis of two different lupus-prone mouse models deficient in BCMA, we identify BCMA as an important factor in regulating peripheral B cell expansion, differentiation, and survival. We demonstrate that a BCMA deficiency combined with the lpr mutation or the murine lupus susceptibility locus Nba2 causes dramatic B cell and PC lymphoproliferation, accelerated autoantibody production, and early lethality. This study unexpectedly reveals that BCMA works to control B cell homeostasis and self-tolerance in systemic autoimmunity.

The tumour necrosis factor/TNF receptor superfamily: therapeutic targets in autoimmune diseases

Autoimmune diseases are characterized by the body's ability to mount immune attacks on self. This results from recognition of self-proteins and leads to organ damage due to increased production of pathogenic inflammatory molecules and autoantibodies. Over the years, several new potential therapeutic targets have been identified in autoimmune diseases, notable among which are members of the tumour necrosis factor (TNF) superfamily. Here, we review the evidence that certain key members of this superfamily can augment/suppress autoimmune diseases.

Abrogation of pathogenic IgG autoantibody production in CD40L gene-deleted lupus-prone New Zealand Black mice

New Zealand Black (NZB) mice spontaneously develop a lupus-like autoimmune disease. Since CD40-CD40L interactions are important for B cell class-switch recombination and germinal center formation, we sought to understand the impact of these interactions on the immune abnormalities in NZB CD40L gene-deleted (CD40L(-/-)) mice in vivo. NZB.CD40L(-/-) mice demonstrated abrogation of all IgG autoantibodies tested and attenuated kidney disease. However, polyclonal B cell activation in vivo and B cell proliferation and class-switching in response to TLR ligands in vitro were preserved in the absence of CD40L in NZB mice. Although, plasmacytoid dendritic cell expansion and elevated BAFF production were unaffected by the absence of CD40L, there was some evidence that IFN-α-induced gene expression was reduced in the bone marrow of NZB.CD40L(-/-) mice. Our results suggest that CD40-CD40L interactions play an important role in promoting pathogenic IgG autoantibody production and kidney disease in NZB mice.

Autoimmunity as a Predisposition for Infectious Diseases

Autoimmunity refers to an inappropriate immune response against self-components of the host that results in pathological conditions. Autoimmune diseases are characterized by an activation of autoreactive T and B cells, are associated in some cases with the production of pathogenic autoantibodies against self-molecules, culminating in inflammation and tissue damage. The reasons for the breakdown of tolerance mechanisms leading to autoimmunity are not clearly known. However, a combination of genetic, immunological, and environmental factors plays a critical role in the pathogenesis of autoimmunity [1]–[5].

Treatment of Type B Insulin Resistance: A Novel Approach to Reduce Insulin Receptor Autoantibodies

Type B insulin resistance belongs to a class of diseases caused by an autoantibody to a cell surface receptor. Blockade of insulin action results in hyperglycemia, hypercatabolism, severe acanthosis nigricans, and hyperandrogenism in women. This rare autoimmune disorder has been treated with various forms of immunosuppression with mixed success. We describe 14 patients with type B insulin resistance referred to the National Institutes of Health, adding to an existing cohort of 24 patients. This report focuses on seven patients who were treated with an intensive combination protocol of rituximab, cyclophosphamide, and pulse corticosteroids aimed at control of pathogenic autoantibody production. Hematological, metabolic, and endocrine parameters, including fasting glucose, glycated hemoglobin, insulin dose, lipids, and testosterone, were monitored before and after treatment. All seven treated patients achieved remission, defined as amelioration of hyperglycemia, discontinuation of insulin therapy, and resolution of hyperandrogenism. Glycated hemoglobin has normalized in all seven treated patients. Remission was achieved on average in 8 months from initiation of treatment. The medication regimen was well tolerated, with no serious adverse events. In seven patients with type B insulin resistance, standardized treatment with rituximab, cyclophosphamide, and pulse steroids results in remission of the disease. Future studies will determine whether this treatment protocol can be applied to other autoantibody/cell surface receptor disease states.

Expression of SSA antigen epitopes in minor salivary glands from patients with primary Sjögren's syndrome

To investigate the correlation between the differential expression of 60 000 SSA epitopes in minor salivary glands (MSG) from patients with primary Sjögren's syndrome (pSS) and glandular inflammation. The screening and soluble expression of single-chain fragment V monoclonal antibodies (Scfv McAb) against SSA antigen epitopes (P1: 480 - 494, P2: 310 - 323 and P3: 230 - 241) were performed by phagemid antibody expression system. The expression of epitopes was detected by immunohistochemical assay (IH) in minor salivary glands from these patients. The correlation between epitopes expression and glandular inflammation was analyzed quantitatively. Immunohistochemical assay of MSG with McAb against P1-P3 epitopes showed that the epithelial cells of glandular tubes and striated duct were stained in membrane and cytoplasm. The expression of P1 epitope was higher than the other two in grading score (chi(2) = 12.94, P < 0.01). And a positive correlation was found between the extent of glandular infiltration and the grade of P1 epitope expression (t = 2.27, P < 0.05) but not with P2 or P3 epitope. Aberrant redistribution of intracellular SSA antigen epitopes onto the cell membrane of involved cells may break the immune tolerance and thus induce the production of pathogenic autoantibodies involved in triggering and maintaining the tissue-specific autoimmune response in pSS MSG. A significantly high membranous expression of P1 and a positive correlation between P1 and the inflammation of MSG suggest that P1 may be the dominant determinant of the antigen-driven immune response in pSS.

IL-17 downregulates p50 and p105 to sustain efficient active NF-κB signaling responses in the splenic B cells of autoimmune BXD2 mice (143.48)

Abstract Constitutively active NF-κB signaling with increased expression of p50 is associated with many autoimmune diseases. In autoimmune BXD2 mice, there is dramatically higher p50 in splenic B cells, compared to B6 B cells (&amp;gt;10.0-fold, p&amp;lt;0.01). Surprisingly, both p50 and p105 in BXD2 B cells are significantly lower than those in B cells from BXD2-Il17ra-/- mice, indicating IL-17 downregulates them in B cells. Consistent with it, administration of AdIL-17RA:Fc which blocks IL-17RA signaling, resulted in significantly increased p50 and p105 and decreased phospho-p65 in splenic B cells, leading to decreased autoantibody production in BXD2 mice. In contrast, administration of AdIL-17A exhibited opposite effects. Stimulation of BXD2 B cells with IL-17 led to cytoplasmic translocation of p50 from the nucleus while p65 was phosphorylated and translocated to the nucleus. In BXD2-Il17ra-/- B cells, there is increased localization of p50 and p105 in the nucleus, compared to BXD2 B cells. The enhanced nuclear p50 and p105 in BXD2-Il17ra-/- B cells are associated with dramatically decreased LPS induction of NF-κB response genes including Rgs which are essential for development of autoreactive germinal centers, indicating higher p50 and p105 inhibit these genes expression in BXD2-Il17ra-/- B cells. The results suggest IL-17 downregulate p50 and p105 to sustain efficient active NF-κB signaling responses in autoreactive BXD2 B cells and result in increased production of pathogenic autoantibodies.

IL-17-producing T cells can augment autoantibody-induced arthritis

Rheumatoid arthritis is a T lymphocyte-mediated disorder, but the precise nature of T cell involvement remains unclear. In the K/BxN mouse model of inflammatory arthritis, T cells initiate disease by providing help to B cells to produce arthritogenic autoantibodies. Here, we have characterized an additional, nonhumoral role for T cells in promoting autoantibody-induced arthritis. Autoreactive KRN T cells introduced either by direct transfer or bone marrow transplantation into B-cell-deficient hosts enhanced K/BxN serum-transferred arthritis, an effect that was dependent on expression of the cognate MHC-molecule/peptide complex. The T cell influence was dependent on interleukin (IL)-17; in contrast, standard serum-transferred arthritis, unenhanced by the addition of T cells, was unaffected by IL-17 neutralization. An IL-17-producing population of transferred KRN T cells was identified and found to be supported by the cotransfer of arthritogenic autoantibodies. IL-17-producing KRN T cells were enriched in inflamed joints of K/BxN mice, suggesting either selective recruitment or preferential differentiation. These results demonstrate the potential for autoreactive T cells to play two roles in the development of arthritis, both driving the production of pathogenic autoantibodies and bolstering the subsequent inflammatory cascade dependent on the innate immune system.

Neutralization of IL-17 inhibits the production of anti-ANT autoantibodies in CVB3-induced acute viral myocarditis

Anti-adenine nucleotide translocator (ANT) autoantibodies are related to the development of Coxsackievirus B3 (CVB3)-triggered acute viral myocarditis (AVMC). Recently, studies suggested that IL-17 especially produced by a novel CD4 + Th-cell subset Th17 cells contributed to the production of pathogenic autoantibodies in some autoimmune diseases. However, the pathogenic role of IL-17 in AVMC remains largely unknown. In this study, we investigated whether IL-17 was associated with the disease progression and the production of anti-ANT autoantibodies in AVMC mouse model. The results showed that IL-17 monoclonal antibody (mAb)-treated AVMC mice had decreased HW/BW, reduced serum CK-MB activity and improved pathological score of heart sections along with the reduction of circulating IL-17 level and serum anti-ANT autoantibodies. The correlation index of serum IL-17 concentration and anti-ANT-autoantibody level was 0.874, p < 0.01. In addition, the experimental results in vitro further proved that IL-17mAb could inhibit the proliferation of CD19 + B lymphocytes and the secretion of anti-ANT autoantibodies. Our data suggested that IL-17 was related to the disease progression in AVMC mouse model by regulating the production of autoantibodies and blocking IL-17 might represent a promising novel therapeutic approach.

B cells twist and shout

B cells twist and shout

Augmented TLR9-induced Btk activation in PIR-B–deficient B-1 cells provokes excessive autoantibody production and autoimmunity

Pathogens are sensed by Toll-like receptors (TLRs) expressed in leukocytes in the innate immune system. However, excess stimulation of TLR pathways is supposed to be connected with provocation of autoimmunity. We show that paired immunoglobulin (Ig)-like receptor B (PIR-B), an immunoreceptor tyrosine-based inhibitory motif–harboring receptor for major histocompatibility class I molecules, on relatively primitive B cells, B-1 cells, suppresses TLR9 signaling via Bruton's tyrosine kinase (Btk) dephosphorylation, which leads to attenuated activation of nuclear factor κB p65RelA but not p38 or Erk, and blocks the production of natural IgM antibodies, including anti-IgG Fc autoantibodies, particularly rheumatoid factor. The autoantibody production in PIR-B–deficient (Pirb−/−) mice was further augmented in combination with the Faslpr mutation, which might be linked to the development of autoimmune glomerulonephritis. These results show the critical link between TLR9-mediated sensing and a simultaneously evoked, PIR-B–mediated inhibitory circuit with a Btk intersection in B-1 cells, and suggest a novel way toward preventing pathogenic natural autoantibody production.

Suppression of murine SLE by oral anti-CD3: inducible CD4+CD25-LAP+ regulatory T cells control the expansion of IL-17+ follicular helper T cells.

Lupus is an antibody-mediated autoimmune disease. The production of pathogenic, class switched and affinity maturated autoantibodies in lupus is dependent on T cell help. A potential mechanism of disease pathogenesis is a lack of control of pathogenic T helper cells by regulatory T cells in lupus. It has been repeatedly shown that the naturally occurring CD4+CD25+ regulatory T cells in lupus prone mice and patients with SLE are defective both in frequency and function. Thus, the generation of inducible regulatory T cells that can control T cell help for autoantibody production is a potential avenue for the treatment of SLE. We have found that oral administration of anti-CD3 monoclonal antibody attenuated lupus development and arrested on-going disease in lupus prone SNF1 mice. Oral anti-CD3 induces a CD4+CD25-LAP+ regulatory T cell that secrets high levels of TGF-beta and suppresses in vitro in TFG-beta-dependent fashion. Animals treated with oral anti-CD3 had less glomerulonephritis and diminished levels of anti-dsDNA autoantibodies. Oral anti-CD3 led to a downregulation of IL-17+CD4+ICOS-CXCR5+ follicular helper T cells, CD138+ plasma cells and CD73+ mature memory B cells. Our results show that oral anti-CD3 induces CD4+CD25-LAP+ regulatory T cells that suppress lupus in mice and is associated with downregulation of T cell help for autoantibody production.

Anti-desmoglein 1 antibodies in healthy related and unrelated subjects and patients with pemphigus foliaceus in endemic and non-endemic areas from Tunisia

Pemphigus foliaceus is an autoimmune blistering skin disease characterized by the production of pathogenic IgG autoantibodies directed against desmoglein 1. To determine the prevalence of anti-desmoglein 1 antibodies in healthy subjects and their distribution in the different regions of Tunisia and to better identify endemic areas of pemphigus foliaceus. We tested, by enzyme-linked immunoserbent assay, sera of 270 normal subjects recruited from different Tunisian areas and 203 related healthy relatives to 90 Tunisian pemphigus foliaceus patients. Results Seventy-six patients (84.4%), 20 healthy controls (7.4%), and 32 relatives (15.76%) had anti-desmoglein 1 antibodies. In southern regions where pemphigus foliaceus is associated with a significant sex ratio imbalance (9 female : 1 male in the south vs. 2.3 : 1 in the north) and a lower mean age of disease onset (33.5 in the south vs. 45 years in the north), a higher prevalence of anti-desmoglein 1 antibodies in healthy controls was observed (9.23% vs. 5.71% in the north). Interestingly, the highest prevalence of anti-desmoglein 1 antibodies in healthy relatives (up to 22%) was observed in the most rural southern localities. More than half anti-desmoglein 1-positive healthy controls were living in rural conditions with farming as occupation, which suggests that this activity may expose the subjects to particular environmental conditions. These results show that the endemic features of Tunisian pemphigus foliaceus are focused in these southern areas more than in other areas and that both environmental and genetic factors contribute to the disease.