Human anti-FcepsilonRIalpha autoantibodies isolated from healthy donors cross-react with tetanus toxoid

Immunological events in chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a highly debilitating skin disease associated with systemic features. We have made significant progress in several aspects relating to this condition. However, the exact physiopathology remains unknown. There is mounting evidence for an autoimmune basis, demonstrated by the CSU serum ability to activate healthy donors skin mast cells and blood basophils. However, it is only seen among 35–40% of patients. Mast cells and basophils play an important role in this skin condition. Both cells in CSU patients have unique features that differentiate them from basophils and mast cells from healthy donors. In the case of basophils, basopenia is typically found in CSU patients. Basophils from CSU patients also tend to be hyporesponsive to stimuli that act through the IgE receptor, responsive to other stimuli as MCP-1 or C5a, and hyperesponsive when incubated with sera. Eosinophils are also present in CSU skin biopsies, yet their exact role has not yet been defined. Likewise, endothelial cells also play a function, as indirectly demonstrated by an increase of vasoactive peptides in skin and plasma of CSU patients’ samples. All these facts orchestrate a systemic inflammation response producing a significant increase of several inflammatory markers. Unfortunately, we lack a unitary model that could explain the exact role of each of these players. In this review, we will describe the history and discover the pathway to the present knowledge on the immunological facts of this disease.

A rapid method of detecting autoantibody against FcεRIα for chronic spontaneous urticaria

Background

Chronic spontaneous urticaria (CU) is a common skin disorder, with an estimated prevalence of 0.5–1.8% in most populations. Around 30–50% of CU patients have an autoimmune etiology, with autoantibodies (autoAbs) against IgE, FcεRIα, and FcεRII/CD23. Although the in vivo autologous serum skin test (ASST) and in vitro histamine release/activation assay are the most frequently used screening methods, these two have many limitations and do not directly measure susceptible autoAbs. This study aimed to establish an in vitro rapid screening test using recombinant autoantigen FcεRIα(rFcεRIα) to improve the diagnosis of autoimmune urticaria.

Methods

Forty patients with CU and 20 healthy individuals were enrolled. After PCR-based cloning and the production of extracellular fragments of the FcεRIαprotein using the E. coli expression system, serum autoAb to rFcεRIαwas evaluated using in-house ELISA and rapid immunodot test.

Results

In ELISA-based detection, 14 out of 20 CU-ASST(+) patients exhibited anti- FcεRIαresponses, whereas five of the 20 CU-ASST(-) and two of the 20 non-CU patients showed autoantibody background in the assay. For the immunodot test, 55% (11/20) of the CU-ASST(+) sera exhibited anti-FcεRIαreactivity. There was no false positive among the CU-ASST(-) and non-CU groups. Using clinical urticaria plus ASST(+) as the gold standard, in-house ELISA had 70% sensitivity, 82.5% specificity, and positive likelihood ratio of 4, while immunodot had 55% sensitivity, 100% specificity, and positive likelihood ratio >55.

Conclusions

This study has developed a rapid immunodot method with high specificity for detecting autoAb to FcεRIαin patients with CU. Preliminary data indicates that this immunodot technique has the potential to be a routine diagnostic assay for autoimmune CU.

Chronic urticaria: recent advances

Chronic urticaria is an umbrella term, which encompasses physical urticarias, chronic "idiopathic" urticaria and urticarial vasculitis. It is important to recognize patients with physical urticarias as the investigation and treatment differs in important ways from patients with idiopathic chronic urticaria or urticarial vasculitis. Although relatively uncommon, urticarial vasculitis is an important diagnosis to make and requires histological confirmation by biopsy. Underlying systemic disease and systemic involvement, especially of the kidneys, should be sought. It is now recognized that chronic "idiopathic" urticaria includes a subset with an autoimmune basis caused by circulating autoantibodies against the high affinity IgE receptor (FceR1) and less commonly against IgE. Although the autologous serum skin test has been proven useful in prompting search for and characterization of circulating wheal-producing factors in chronic urticaria, its specificity as a screening test for presence of functional anti-FceR1 is low, and confirmation by demonstration of histamine-releasing activity in the patient's serum must be the benchmark test in establishing this diagnosis. Improved screening tests are being sought; for example, ability of the chronic urticaria patient's serum to evoke expression of CD 203c on donor human basophils is showing some promise. The strong association between autoimmune thyroid disease and autoimmune urticaria is also an area of ongoing research. Drug treatment continues to be centered on the H1 antihistamines, and the newer second-generation compounds appear to be safe and effective even in off-label dosage. Use of systemic steroids should be confined to special circumstances such as tapering regimens for acute flare-ups. Use of leukotriene antagonists is becoming popular, but the evidence for efficacy is conflicting. Cyclosporin is also effective and can be used in selected cases of autoimmune urticaria, and it is also effective in non-autoimmune cases, although less so.

Progress and challenges in the understanding of chronic urticaria

: Chronic urticaria is a skin disorder characterized by transient pruritic weals that recur from day to day for 6 weeks or more. It has a great impact on patients' quality of life. In spite of this prevalence and morbidity, we are only beginning to understand its physiopathology and we do not have a curative treatment. Moreover, a patient with chronic urticaria may undergo extensive laboratory evaluations seeking a cause only to be frustrated when none is found. In recent years there have been significant advances in our understanding of some of the molecular mechanisms responsible for hive formation. The presence and probable role of IgG autoantibodies directed against epitopes expressed on the alpha-chain of the IgE receptor and to lesser extent, to IgE in a subset of patients is generally acknowledged. These autoantibodies activate complement to release C5a, which augments histamine release, and IL4 and leukotriene C4 are released as well. A perivascular cellular infiltrate results without predominance of either Th1 or Th2 lymphocyte subpopulations. Basophils of all chronic urticaria patients (autoimmune or idiopathic) are hyperresponsive to serum, regardless of source, but poorly responsive to anti IgE. In this review we will summarize the recent contributions to this field and try to provide insights to possible future directions for research on this disease.

Yersinia rLcrV and rYopB inhibits the activation of murine peritoneal macrophages in vitro

Yersinia antigenic proteins LcrV and YopB are translocators of effector Yops in type III secretion system. Recently, we have reported that rLcrV and rYopB inhibit the production of TNF-alpha, IFN-gamma, and IL-12 in murine peritoneal macrophages. It was also demonstrated that IL-10 and TLR2 signaling pathways and inhibition of MAPK cascade is involved in rLcrV- and rYopB-induced immunomodulation. In the present study, it is reported that rLcrV and rYopB inhibited the LPS-induced production of IL-1beta in macrophages. Pretreatment of macrophages with rLcrV and rYopB also inhibited the LPS-induced transcription of IL-6 but not of GM-CSF. However, the transcription of chemokines like MCP-1, MIP-1alpha, MIP-1beta, and RANTES were inhibited by rLcrV and rYopB. Both proteins also affected the cytoskeleton and lipid rafts in macrophages. It is further observed that IL-10 antibodies abrogated the rLcrV- and rYopB-induced inhibition of IL-1beta production in LPS-treated macrophages. The data, therefore, suggests a possible role of IL-10 in rLcrV and rYopB mediated inhibition of LPS-induced production of IL-1beta in macrophages.

Yersinia V antigen induces both TLR homo- and heterotolerance in an IL-10-involving manner

The virulence antigen (LcrV) of pathogenic yersiniae "silences" macrophages against stimulation with the TLR2-agonist zymosan A in a CD14/TLR2-dependent fashion via IL-10 induction. This pathogenically important "silencing" resembles TLR tolerance phenomena; in these, pre-exposure to a primary tolerizing TLR-agonist renders macrophages unresponsive to stimulation with a secondary challenging TLR-agonist which may involve either the same (TLR homotolerance) or a different TLR (TLR heterotolerance) as the primary TLR-agonist. Here, we show that rLcrV induces TLR homo- and heterotolerance against TLR2- or TLR4-agonists both in human and murine macrophages, respectively. The underlying mechanism of LcrV-induced tolerance is most likely not due to changes in TLR2- or TLR4 expression, but involves LcrV-mediated IL-10 production, since LcrV-induced TLR homo- and heterotolerance is highly impaired in IL-10(-/-) macrophages. Moreover, the involvement of IL-10 in TLR tolerance induction seems to be a more general phenomenon as shown by experiments using different TLR-agonists in IL-10(-/-) macrophages. Since LcrV acts as a secreted protein upon macrophages without requiring direct cell contact, as shown in transwell assays, we propose that yersiniae exploit IL-10-involving TLR tolerance mechanisms by the virulence factor LcrV.

Effect of rLcrV and rYopB from Yersinia pestis on murine peritoneal macrophages in vitro

The interaction between macrophages and bacterial pathogens is crucial in the pathogenesis of infectious diseases. The 70 kb plasmid encodes low calcium response V (LcrV) or V antigen and a group of highly conserved yersinia outer proteins (Yops) are essential for full virulence. In present study, we investigated the effect of rLcrV and rYopB on macrophage functions in vitro. It is observed that rLcrV and rYopB inhibited the LPS induced expression of TNF-alpha, IFN-gamma, KC, IP-10, and IL-12 in macrophages. rLcrV and rYopB caused increased expression of IL-10 and TLR2, whereas inhibited TLR4 expression in LPS treated macrophages. IL-10 and TLR2 antibodies reversed the rLcrV and rYopB induced inhibition of TNF-alpha production by LPS treated macrophages, whereas IL-4 and TLR4 antibodies had no effect. Our data suggests a possible role of IL-10 and TLR2 in rLcrV and rYopB mediated inhibition of macrophage function.

Effect of low- and high-virulence Yersinia enterocolitica strains on the inflammatory response of human umbilical vein endothelial cells

Pathogenic strains of Yersinia spp. inject a set of Yop effector proteins into eukaryotic cells by using a plasmid-encoded type III secretion system. In this study, we analyzed the inflammatory response of human umbilical vein endothelial cells (HUVECs) after infection with different Yersinia enterocolitica strains. We found that both expression of intercellular adhesion molecule 1 and release of the cytokines interleukin-6 (IL-6) and IL-8 by HUVECs are downregulated in a YopP-dependent way, demonstrating that YopP plays a major role in the inflammatory response of these cells. Infection of HUVECs with several low-virulence (biotype 2, 3, and 4) and high-virulence (biotype 1B) Y. enterocolitica strains showed that biotype 1B isolates are more efficient in inhibiting the inflammatory response than low-virulence Y. enterocolitica strains and that this effect depends on the time of contact. We extended the results of Ruckdeschel et al. and found that on the basis of the presence or absence of arginine-143 of YopP (K. Ruckdeschel, K. Richter, O. Mannel, and J. Heesemann, Infect. Immun. 69:7652-7662, 2001) all the Y. enterocolitica strains used fell into two groups, which correlate with the low- and high-virulence phenotypes. In addition, we found that high-virulence strains inject more YopP into the cytosol of eukaryotic target cells than do low-virulence strains.

Yersinia enterocolitica evasion of the host innate immune response by V antigen-induced IL-10 production of macrophages is abrogated in IL-10-deficient mice

The virulence-associated V Ag (LcrV) of pathogenic Yersinia species is part of the translocation apparatus, required to deliver antihost effector proteins (Yersinia outer proteins) into host cells. An orthologous protein (denoted as PcrV) has also been identified in the ExoS regulon of Pseudomonas aeruginosa. Additionally, it is known that LcrV is released by yersiniae into the environment and that LcrV causes an immunosuppressive effect when injected into mice. In this study, we demonstrate for the first time that rLcrV, but not PcrV, is capable of suppressing TNF-alpha production in zymosan A-stimulated mouse macrophages and the human monocytic Mono-Mac-6 cell line. The underlying mechanism of TNF-alpha suppression could be assigned to LcrV-mediated IL (IL)-10 production, because 1) LcrV induces IL-10 release in macrophages, 2) anti-IL-10 Ab treatment completely abrogated TNF-alpha suppression, and 3) TNF-alpha suppression was absent in LcrV-treated macrophages of IL-10-deficient (IL-10-/-) mice. The relevance of LcrV-mediated immunosuppression for the pathogenicity of yersiniae became evident by experimental infection of mice; in contrast to wild-type mice, IL-10-/- mice were highly resistant against Yersinia infection, as shown by lower bacterial load in spleen and liver, absent abscess formation in these organs, and survival.

Evaluation of chronic urticaria in patients with Hashimoto thyroiditis

The coincidence of Hashimoto thyroiditis (HT) and chronic idiopathic urticaria (CIU) is a commonly observed phenomenon in western New York. Previous literature suggested that there may be a direct relationship between them. We undertook these studies to determine whether humoral or cell-mediated mechanisms might link HT and CIU. Skin biopsies from patients with CIU, with or without HT, were indistinguishable by light microscopy. No immune complex deposition was observed, although only the skin from patients with CIU and HT contained perivascular fibrin deposits. Similarly, immunohistochemical studies evaluating cellular expression of CD3, CD4, CD8, CD20, and CD68 failed to differentiate between CIU with or without HT. Analysis of Vbeta restriction in thyroid tissue of patients with HT and the skin of patients with CIU and HT by in situ polymerase chain reaction failed to reveal any oligoclonal T-lymphocyte subpopulations. In contrast, only patients with CIU and HT had anti-FcepsilonRI antibodies in their sera that could induce degranulation of normal basophils. Some sera from patients with CIU and HT caused degranulation of normal basophils in the absence of anti-FceRI. The factor causing basophil degranulation in these sera was not determined. Patients with CIU and HT failed to improve clinically with thyroid replacement therapy. All CIU patients were equally well managed with symptomatic therapies. In conclusion, HT likely represents a marker of other autoimmunity, rather than being a direct causative agent in CIU. Management of CIU, with or without HT and with or without anti-FceRI antibodies, should be the same. Future studies will have to examine whether cell-mediated responses participate in CIU, especially in association with HT.

Autoimmunity in chronic urticaria and urticarial vasculitis

In contrast to acute urticaria, etiology cannot be identified in most cases of chronic urticaria. Recent evidence suggests that a subset of patients with chronic urticaria may have an autoimmune basis for their condition. The demonstration of antithyroid autoantibodies in some patients with chronic idiopathic urticaria (CIU) provides support for an association. However, the discovery of a positive skin test response to intradermal injection of autologous serum in as many as 60% of patients with CIU led to the identification of autoantibodies to IgE and the alpha-chain of the high-affinity IgE receptor, Fc epsilon RI alpha. Additional studies have demonstrated that some of these autoantibodies are capable of releasing histamine from donor basophils and mast cells. This article reviews the literature that addresses a possible autoimmune etiology in a subset of patients with CIU. Urticarial vasculitis is differentiated from chronic urticaria based on clinical features and biopsy findings of leukocytoclastic vasculitis. Most cases of urticarial vasculitis are secondary to an underlying systemic disease. The presence of autoantibodies has also been demonstrated in a subset of patients with primary urticarial vasculitis. This article briefly reviews some of this data.

Mimicry of human IgE epitopes by anti-idiotypic antibodies

According to Jerne's network hypothesis, the binding site of an anti-idiotypic antibody also represents the internal image of an epitope present on a foreign, or even a self antigen. In recent years, antigen mimicry has been defined at the molecular level for some xeno-antigens. However, until now there has been no demonstration of structural mimicry between a human anti-idiotypic antibody and a self structure. To address this question, we used human IgE as the self structure and a well-defined anti-human IgE mAb (BSW17). We describe the isolation of two anti- idiotypic antibodies specific for the anti-IgE antibody BSW17 from a non-immune human Fab phage display library. Interestingly, these two anti-idiotypic antibodies mimic the same molecular surface region as a previously described IgE peptide mimotope isolated by panning on BSW17, but they cover a much larger epitope on the IgE molecule. Accordingly, immunisation of rabbits with the two anti-idiotypic antibodies induced high-affinity antibodies with the same characteristics as BSW17. Thus, our data demonstrate that it is possible to isolate anti-idiotypic antibodies derived from the human genome without the need for hyperimmunization, and confirm Jerne's hypothesis that both foreign antigens and self structures can be mimicked by our own immunoglobulins.

Tumor necrosis factor receptor p55-deficient mice respond to acute Yersinia enterocolitica infection with less apoptosis and more effective host resistance

Tumor necrosis factor (TNF) has generally been regarded as a protective cytokine in host defense against bacterial infections. In the present study, we evaluated the role of TNF in the acute phase of infection by Yersinia enterocolitica by using mice rendered genetically deficient in TNF receptor p55 (TNFRp55(-/-)). Unexpectedly, TNFRp55(-/-) mice showed more effective resistance to the bacteria, reflected in enhanced bacterial clearance and less tissue damage, than did control C57BL/6 mice. C57BL/6 mice showed evidence of extensive apoptosis in the spleen accompanied by a selective decrease in the CD4(+)-T-cell population of splenocytes, whereas TNFRp55(-/-) mice were spared these changes. The splenocytes from TNFRp55(-/-) mice also maintained a robust gamma interferon IFN-gamma response to mitogenic stimulation, while the comparable response in C57BL/6 mice was impaired. In addition, splenocytes harvested from infected mice demonstrated lower production of interleukin-10 IL-10 in TNFRp55(-/-) mice than in C57BL/6 mice. These findings suggest that Yersinia can induce TNFRp55-mediated apoptosis of splenocytes in the acute phase of the infection and that alteration of T-cell-generated cytokines can dramatically alter the early events in host defense against this pathogen.

Interferon consensus sequence binding protein confers resistance against Yersinia enterocolitica

Interferon consensus sequence binding protein (ICSBP)-deficient mice display enhanced susceptibility to intracellular pathogens. At least two distinct immunoregulatory defects are responsible for this phenotype. First, diminished production of reactive oxygen intermediates in macrophages results in impaired intracellular killing of microorganisms. Second, defective early interleukin-12 (IL-12) production upon microbial challenge leads to a failure in gamma interferon (IFN-gamma) induction and subsequently in T helper 1 immune responses. Here, we investigated the role of ICSBP in resistance against the extracellular bacterium Yersinia enterocolitica. ICSBP(-/-) mice failed to produce IL-12 and IFN-gamma, but also IL-4, after Yersinia challenge. In addition, granuloma formation was highly disturbed in infected ICSBP(-/-) mice, leading to multiple necrotic abscesses in affected organs. Consequently, ICSBP(-/-) mice rapidly succumbed to acute Yersinia infection. In vitro treatment of spleen cells from ICSBP(-/-) mice with recombinant IL-12 (rIL-12) or rIL-18 in combination with a second stimulus resulted in IFN-gamma induction. In experimental therapy of infected ICSBP(-/-) mice, we observed that administration of rIL-12 induced IFN-gamma production which was associated with improved resistance to Yersinia. In contrast, treatment with rIL-18 failed to enhance endogenous IFN-gamma production but nevertheless reduced bacterial burden in ICSBP(-/-) mice. Although cytokine therapy with rIL-12 or rIL-18 ameliorated the course of Yersinia infection in ICSBP(-/-) mice, both cytokines failed to completely restore impaired immunity. Taken together, the results indicate that the transcription factor ICSBP is essential for efficient host immune defense against Yersinia. These results are important for understanding the complex host immune responses in bacterial infections.