Polyclonal B-cell Activation Research Articles

The Absence of CD44 Ameliorates Faslpr/lpr Disease

The lpr mutation in the Fas gene leads to symptoms of autoimmune disease, including polyclonal B-lymphocyte activation and lymphoproliferation. The expanding T-lymphocyte populations in the disease are characterized by high expression levels of the memory marker CD44. It has not been known whether CD44 expression contributes to the pathophysiology of the condition or merely reflects a consequence of excessive lymphocyte activation. We therefore tested the role of CD44 gene products in Faslpr/lpr disease in gene targeted mice. We bred CD44 knockout mice and C57Bl/6-lpr mice to generate the Faslpr/lpr CD44+/+, and Faslpr/lpr CD44−/− genotypes and analyzed the disease manifestations around 215 days of age. The absence of CD44 substantially reduced the immunoglobulin secretion and lymphocyte expansion that are characteristic of the Faslpr/lpr syndrome. Surprisingly, the percentage of CD3+CD4−CD8− (double negative) cells in peripheral lymphoid organs increased in Faslpr/lpr CD44−/− mice almost to the same extent as in Faslpr/lpr CD44+/+ mice. These results indicate that the expansion of the fraction of double negative cells in spleens and lymph nodes, believed to be generated by down-regulation of CD8, does not depend on increased lymphocyte numbers. Furthermore, they corroborate an essential role for CD44 gene products in the T-cell expansion and polyclonal B-cell activation that constitute the Faslpr/lpr syndrome. The CD44 receptor may be a suitable therapeutic target for inhibition of lymphoproliferation in autoimmune diseases.

Non-specific elevation of antistreptolysin antibody (ASO) in the absence of streptococcal pharyngitis

Rationale Elevated antistreptolysin antibody (ASO) has been found in five patients without history, physical findings, rapid antigen tests or cultures suggestive of streptococcal pharyngitis. Methods Histories and data are reviewed. Results 1. JK, 10 year old male, presented with urticaria, lymphadenopathy and oral ulcers following treatment with amoxycillin and clarithromycin. Past history included recent Stevens-Johnson syndrome. Laboratory tests: elevated antinuclear antibodies (1:320), elevated erythrocyte sedimentation rate, neutropenia and massive elevation of ASO at 2,638 (0-200 IU/ml). Diagnosed with drug induced lupus. 2. JA, 56 year old, with hyper-IgM syndrome and bronchiectasis, treated with intravenous immunoglobulin (IVIG), presented with leukocytoclastic angiitis. Laboratory tests: positive antineutrophil cytoplasmic antibodies (ANCA) and suppressed complement. Two months after discontinuation of IVIG ASO was 91 U/dL (0-85) but eventually normalized. Reintroduction of IVIG was tolerated without elevation of ANCA or ASO. 3. KB, 19 year old female, referred for recurrent sinusitis, lymphadenopathy, buccal ulcers and recent mononucleosis, had elevated antinuclear antibodies and suppressed complement. ASO has been borderline (84 U/dL) and mildly elevated (96 U/dL, reference: 0-85). Diagnosed with Sjoegren syndrome. 4. TS, 35 year old, presented with chronic urticaria for 6 years, started shortly after his diagnosis with Guillain-Barre syndrome. Chronic inflammatory demyelinating polyneuropathy is possible. ASO titers vary from 71 to 95 U/dL (reference 0-85). 5. DM, 7 year old, presented with angioedema-urticaria, due to penicillin allergy. ASO titer was 242 U/dL (reference 0-200). Conclusions Elevated ASO titers occur without streptococcal pharyngitis. Polyclonal activation of B-cells due to autoimmunity, drug allergy or viral infections, is a likely mechanism.

Metallic tin is an adjuvant for anaphylaxis in rats.

Metallic tin powder is known to have an adjuvant-like property, by which it increases the levels of natural antibodies and induced hemagglutinins, and it enhances the induction of allergic encephalomyelitis in rats. In the present work, metallic tin is shown to be an adjuvant for a different immunologic process, anaphylactic sensitization. The new data support the notion that metallic tin causes polyclonal B-cell activation with proliferation of plasma cells.

Dose–response study of thimerosal-induced murine systemic autoimmunity

The organic compound ethylmercurithiosalicylate (thimerosal), which is primarily present in the tissues as ethylmercury, has caused illness and several deaths due to erroneous handling when used as a disinfectant or as a preservative in medical preparations. Lately, possible health effects of thimerosal in childhood vaccines have been much discussed. Thimerosal is a well-known sensitizing agent, although usually of no clinical relevance. In rare cases, thimerosal has caused systemic immune reactions including acrodynia. We have studied if thimerosal might induce the systemic autoimmune condition observed in genetically susceptible mice after exposure to inorganic mercury. A.SW mice were exposed to 1.25–40 mg thimerosal/l drinking water for 70 days. Antinucleolar antibodies, targeting the 34-kDa protein fibrillarin, developed in a dose-related pattern and first appeared after 10 days in the two highest dose groups. The lowest observed adverse effect level (LOAEL) for antifibrillarin antibodies was 2.5 mg thimerosal/l, corresponding to an absorbed dose of 147 μg Hg/kg bw and a concentration of 21 and 1.9 μg Hg/g in the kidney and lymph nodes, respectively. The same LOAEL was found for tissue immune-complex deposits. The total serum concentration of IgE, IgG1, and IgG2a showed a significant dose-related increase in thimerosal-treated mice, with a LOAEL of 5 mg thimerosal/l for IgG1 and IgE, and 20 mg thimerosal/l for IgG2a. The polyclonal B-cell activation showed a significant dose–response relationship with a LOAEL of 10 mg thimerosal/l. Therefore, thimerosal induces in genetically susceptible mice a systemic autoimmune syndrome very similar to that seen after treatment with inorganic mercury, although a higher absorbed dose of Hg is needed using thimerosal. The autoimmune syndrome induced by thimerosal is different from the weaker and more restricted autoimmune reaction observed after treatment with an equipotent dose of methylmercury.

Effects of deviating the Th2-response in murine mercury-induced autoimmunity towards a Th1-response.

T-helper cells type 1 (Th1) and type 2 (Th2) play an important role in the pathogenesis of autoimmune diseases. In many Th1-dependent autoimmune models, treatment with recombinant interleukin-12 (rIL-12) accelerates the autoimmune response. Mercury-induced autoimmunity (HgIA) in mice is an H-2 regulated condition with antinucleolar antibodies targeting fibrillarin (ANoA), systemic immune-complex (IC) deposits and transient polyclonal B-cell activation (PBA). HgIA has many characteristics of a Th2 type of reaction, including a strong increase of IgE, but disease induction is critically dependent on the Th1 cytokine IFN-gamma. The aim of this study was to investigate if a strong deviation of the immune response in HgIA towards Th1 would aggravate HgIA. Injections of both rIL-12 and anti-IL-4 monoclonal antibody (alpha-IL-4) reduced the HgCl2-(Hg-)induced concentration of the Th2-dependent serum IgE and IgG1, but increased the Th1-dependent serum IgG2a. The IgG-ANoA developed earlier and attained a higher titre after combined treatment, and the ANoA titre of the IgG1 isotype decreased while the ANoA titre of the Th1-associated IgG2a, IgG2b and IgG3-ANoA isotypes increased. Treatment with rIL-12 alone increased the Hg-induced IgG2a and IgG3 ANoA titres, the PBA, and the IC deposits in renal and splenic vessel walls, while treatment with alpha-IL-4 + Hg inhibited renal but not splenic vessel wall IC deposits. We conclude that manipulating the cytokine status, by altering the Th1/Th2 balance, will influence autoimmune disease manifestations. This might be an important way of modulating human autoimmune diseases.

Polyclonal B-cell activation in mice infected by intragastric route with Yersinia enterocolitica O:8.

The infection of mice with virulent and avirulent strains of Y. enterocolitica O: 8 resulted in polyclonal activation of the repertory of spleen and Peyer’s patches B lymphocytes, including some autoreactives clones.

Involvement of cytokines in the pathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is characterized by overt polyclonal B-cell activation and autoantibody (Ab) production. By contrast, cellular immune responses against allo- or recall antigens are significantly impaired. Many evidences indicate that IL-10 overproduction plays a pivotal role in the disease and the contribution of the IL-10/IL-12 imbalance to the pathophysiology of SLE will be extensively discussed. The authors will further summarize the available data about the involvement of IFN-γ, TNF-α, TGF-β and TALL-1. Other cytokines (IL-1, IL-2, IL-4, IL-6, IL-16, IL-17 and IL-18) will be briefly discussed. Numerous abnormalities of the cytokine network have been described in patients suffering from systemic lupus erythematosus as well as in murine lupus models. Some of them were shown to play a pivotal physiopathological role in certain T-cell, B-cell or antigen-presenting cell (APC) dysfunctions characteristic of the disease, while others are more likely to be innocent bystanders. It should be stressed, moreover, that not all the data discussed herein fit into a single picture. The heterogeneity of human SLE, the influence of disease activity and therapy on cytokine production and function, the relative shortage of human lupus peripheral blood-derived mononuclear cells (PBMC), together with the lack of a perfectly-matched animal model, further sophisticate the issue. For these very reasons, this review will focus on the cytokines that the authors wrongly or rightly consider as the major players in the game, namely IL-10, IL-12, TNF-α, IFN-γ and the recently described TALL-1/BLys/BAFF. Before doing so, we felt worthwhile to briefly glance through the major immune abnormalities observed in SLE.

Preparation of polysaccharide-conjugate vaccines.

It was recognized early last century that small molecules, known as haptens, can be made immunogenic after conjugation to carrier proteins (). This principle has since been applied successfully to improve the immunogenicity of (poly)saccharides (,). We now know that the carrier proteins ensure the involvement of T-helper lymphocytes in the activation of the hapten- or polysaccharide-specific antibody-producing B lymphocytes (Fig. 1). In contrast to small molecules or haptens, polysaccharides (or other macromolecules with a repeating structure) are able to induce an immune response, most likely by directly activating B-lymphocytes. Antigens that are able to induce an immune response without the involvement of T-helper lymphocytes are referred to as TI (thymus-independent) antigens () (Table 1). TI-2 antigens, such as plain polysaccharides, are not able to activate relatively immature B-cells. This is in contrast to TI-l antigens, which can activate immature B-cells because of their mitogenic activity. Lipopolysaccharides (LPS) are examples of TI-l antigens. Conventional T-cells recognize peptide sequences in association with the major histocompatibility complex (MHC). Recently, unconventional T-cells were found to recognize (glyco) lipids in a CD1-restricted way, γδT-cells were shown to respond to non-proteinaceous microbial ligands (that may include carbohydrates) in a virtually MHC-unrestricted way (). The findings of T-cell regulation of the immune response against polysaccharides (, , ) without biochemical demonstration of the specificity of the molecular interactions can best be explained by assuming a role for anti-idiotypic antibodies and T-cells specific for the idiotopes (carbohydrate mimotopes) or via the newly discovered unconventional T-cells. Open image in new window Fig. 1. Polysaccharides are poor in activating B-cells to the production of antibodies in children younger than 2 yr of age. If antibodies are formed, they are of short duration. For conjugate vaccines T-cells are involved in the activation of B-cells. Presumably, the conjugate is taken up by polysaccharide-specific B-cells, processed, and presented to carrier-specific T-cells. The involvement of T-cells results in the activation of B-cells to production of antibodies and induction of memory in children younger than 2 yr of age. Table 1 Characteristics of T-Cell Independent Antigens Type 1 Bacterial cell-wall components Mitogenic or polyclonal B-cell activator Stimulate antibody responses in neonates Stimulate antibody responses in CBA/N mice Examples: lipopolysaccharide and hapten derivatives; Brucella abortus Type 2 Polysaccharides, polypeptides, polynucleotides High mol wt, multiple repeating antigenic determinants Slowly metabolized Tolerogenic in large doses or soluble form Activate alternative complement pathway (some) Generate few (if any) memory B-cells Restriction of isotypes induced Lack of affinity maturation Lack of T-cell memory Fail to stimulate antibody responses in neonates Fail to stimulate antibody responses in CBA/N mice Examples: Pneumococcal polysaccharides; Haemophilus influenzaetype b polysaccharide; meningococcal polysaccharides

Imiquimod: A cytokine inducer

J Am Acad Dermatol 2002;47:S205-8.

Tolerance to self gangliosides is the major factor restricting the antibody response to lipopolysaccharide core oligosaccharides in Campylobacter jejuni strains associated with Guillain-Barré syndrome.

Guillain-Barré syndrome following Campylobacter jejuni infection is frequently associated with anti-ganglioside autoantibodies mediated by molecular mimicry with ganglioside-like oligosaccharides on bacterial lipopolysaccharide (LPS). The regulation of antibody responses to these T-cell-independent antigens is poorly understood, and only a minority of Campylobacter-infected individuals develop anti-ganglioside antibodies. This study investigates the response to gangliosides and LPS in strains of mice by using a range of immunization strategies. In normal mice following intraperitoneal immunization, antibody responses to gangliosides and LPS are low level but can be enhanced by the antigen format or coadministration of protein to recruit T-cell help. Class switching from the predominant immunoglobulin M (IgM) response to IgG3 occurs at low levels, suggesting B1-cell involvement. Systemic immunization results in poor responses. In GalNAc transferase knockout mice that lack all complex gangliosides and instead express high levels of GM3 and GD3, generation of anti-ganglioside antibodies upon immunization with either complex gangliosides or ganglioside-mimicking LPS is greatly enhanced and exhibits class switching to T-cell-dependent IgG isotypes and immunological memory, indicating that tolerance to self gangliosides is a major regulatory factor. Responses to GD3 are suppressed in knockout mice compared with wild-type mice, in which responses to GD3 are induced specifically by GD3 and as a result of polyclonal B-cell activation by LPS. The anti-ganglioside response generated in response to LPS is also dependent on the epitope density of the ganglioside mimicked and can be further manipulated by providing secondary signals via lipid A and CD40 ligation.

Infection of simian B lymphoblastoid cells with simian immunodeficiency virus is associated with upregulation of CD23 and CD40 cell surface markers.

Simian immunodeficiency virus (SIV) as well as human immunodeficiency virus (HIV) induce polyclonal B-cell activation and are associated with the appearance of lymphomas in their respective hosts in either the presence or the absence of other co-infecting viruses such as Epstein-Barr virus (EBV). However, the pathogenic role of these retroviruses in the development of lymphoproliferative disorders remains poorly understood. To explore the virus-B-cell interactions, two immortalized lymphoblastoid B-cell lines (SL-P1 and SL-691) were established from cynomolgus monkeys that were naturally co-infected with a simian type D retrovirus-2 (SRV-2) and with the herpes virus Macaca fascicularis (HVMF-1). We addressed their susceptibility to SIV infection and the phenotypic modifications associated with SIV infection. In response, both cell lines (1) were co-infected with HVMF-1 (latent infection) and with SRV-2 (productive infection), (2) had a transformed phenotype because they did not require exogenous growth factors, and (3) when injected into mice with severe combined immunodeficiency (SCID), generated serially transplantable tumors. The B-cell origin of SL cells was demonstrated by the presence of rearrangements of the IgH gene and by the expression of typical B-cell lineage markers, such as CD20. SL-P1 and SL-691 could be discriminated on the basis of different expressions of CD23 and CD40 and of kappa- and lambda-chains. Most importantly, SL-691 cells, but not SL-P1 cells, were susceptible to chronic noncytolytic SIV infection. This infection occurred in a CD4/CCR5/CXCR4-independent manner and was associated with the upregulated expression of CD23 and CD40 cell surface markers. In addition, CD20 expression, which progressively disappeared in SL-691 noninfected cells, was maintained in the SIV-infected counterpart. These findings support the hypothesis that SIV induce phenotypic perturbations in B cells that might eventually contribute to the development of lymphoproliferative disease.

Immunological Responses Are Not Abnormal in Symptomatic Gulf War Veterans

The underlying etiology and pathogenesis of Gulf War veterans' illnesses continue to be under intense investigation. Reports have suggested the basis for these illnesses may be an altered immune system, but compelling evidence is lacking. We sought to determine whether in vitro immune responses were abnormal in symptomatic Gulf War veterans relative to matched controls. A randomized case-control study was conducted by blinded comparison of laboratory measures of in vitro immune responses in blood samples obtained from veterans in an outpatient facility of a Veterans Affairs medical center. Symptomatic Gulf War veterans with otherwise undefined illnesses (52 symptomatic subjects), asymptomatic Gulf War veterans (31 asymptomatic controls), and veterans who had applied for disability compensation and had not participated in the Gulf War (21 disability controls) represented the volunteer sample. In vitro cellular and humoral immune responses were measured to detect functional abnormalities in antigen presenting cells (autologous mixed leukocyte reactions and expression of interleukin (IL)-1beta, IL-6, IL-10, and tumor necrosis factor-alpha); T cells (lymphocyte proliferation using the polyclonal T-cell activators phytohemagglutinin and Concanavalin A; primary immune responses in allogeneic mixed leukocyte reactions; secondary immune response using the recall antigens tetanus toxoid, Candida albicans, and anthrax vaccine; and soluble IL-2 receptor expression); type-1 T-helper cells (gamma interferon expression); type-2 T-helper cells (IL-4 and IL-10 expression); and B cells (polyclonal B-cell activator pokeweed mitogen-induced immunoglobulin production). In general, immune response measures did not differ significantly between groups. Heightened responses observed in the disability control group (sporadically greater responses to one mitogen and two antigens) and the Gulf War participation control group (greater recall responses to anthrax vaccine) did not suggest impaired immune cell function in symptomatic veterans when compared with controls. We conclude that in vitro immunological responses are not abnormal in symptomatic Gulf War veterans.

Spontaneous Downregulation of Antibody/Autoantibody Synthesis in Susceptible Mice upon Chronic Exposure to Mercuric Chloride is not Owing to a General Immunosuppression

Administration of mercuric chloride into susceptible rats and mice induces a systemic autoimmune disease, which is characterized by a T-cell-dependent polyclonal B-cell activation, an increase in serum levels of immunoglobulin (Ig)G1 and IgE, production of antibodies of different specificities and development of renal IgG deposits. A peculiar feature of mercury-induced autoimmunity is that the polyclonal B-cell activation spontaneously disappears in spite of continuous injection of mercury. The exact mechanism(s) for autoregulation of mercury-induced autoimmunity is not well understood. In the present study, we analysed the regulation of mercury-induced immune/autoimmune responses in mice and tested whether spontaneous downregulation of these responses is owing to a general immunosuppression. Mercury-susceptible [SJL (H-2s)] and -resistant [DBA/2 (H-2d)] mice were injected with mercury for 4, 10, 15 and 17 weeks. Immune/autoimmune responses were monitored in these mice. Thereafter, mercury-injected mice for 17 weeks were further immunized with horse red blood cells (HRBC) to study whether the subsequent humoral immune response to a foreign antigen is suppressed. We found that except for IgG1 anti-nucleolar antibody production and renal IgG1 deposition, other characteristics of mercury-induced autoimmunity were downregulated in SJL (H-2s) mice after chronic treatment with mercury. However, these mice did not show any reduction in the number of splenic antibody-secreting cells and/or in serum titres of specific IgM, IgG1 and IgG2a anti-HRBC antibodies in response to HRBC as compared with naïve mice. Similarly, in mercury-resistant DBA/2 (H-2d) mice, chronic treatment with mercury did not either suppress specific antibody responses against HRBC. Our findings show that the autoregulation of mercury-induced immune/autoimmune responses observed after chronic treatment with mercury is not owing to a general immunosuppression.

Isotypes of rheumatoid factors in rheumatoid arthritis and chronic liver diseases

We studied isotype-specific rheumatoid factors (RFs) to clarify their significance in rheumatoid arthritis (RA) and to verify the difference in RF isotypes between RA and chronic liver diseases (CLD). Isotype-specific RFs in RA and in CLD were measured by enzyme-linked immunosorbent assay (ELISA). Most sera (n = 51, 94.1%) from RA patients contained some kind of RF isotypes (92.1% for IgM RF, 76.4% for IgG RF, and 43.1% for IgA RF), and seronegative RA by ELISA was seen in only 11.8% (n = 6). The most characteristic combination of RF isotypes in active RA was IgG, IgA, and IgM. This combination of RF isotypes changed to IgG plus IgM, according to the diminution of RA activity; then, we found only IgM RF in inactive RA. The titers of each RF isotype also decreased in parallel with the activity of RA. IgA RF seemed to be the most sensitive factor for evaluating the activity of RA. In CLD, almost the same high frequency (n = 49, 89.8% for IgM RF, 59.2% for IgG RF), with the same titer levels seen in RA, was observed. On the other hand, IgA RF was significantly lower in frequency (n = 9, 18.4%) and in titer, compared with the finding in RA. Surprisingly, even in CLD, true seronegativity by ELISA was also found in very few patients (n = 4, 8.1%). In CLD, positive RFs detected by agglutination assay were seen more often in chronic hepatitis than in liver cirrhosis. In RA patients, significant associations of IgA RF and the serum concentration of IgA, and IgG RF and the serum concentration of IgG, were observed. On the other hand, in CLD patients, significant associations of IgG RF and the serum IgG concentration, and of IgM RF and the serum IgM concentration, were observed. These results indicated that IgA RF in active RA is the most characteristic RF isotype distinguishing it from other nonrheumatic diseases, as well as from inactive RA. RF isotypes reflected the background polyclonal B-cell activation in different manners in both diseases. In CLD, RF isotypes seemed to be disease-related immunological disorders reflecting disease progression.

Trypanosoma cruzi mitochondrial malate dehydrogenase triggers polyclonal B-cell activation.

It has been proposed that Trypanosoma cruzi, the aetiologic agent of Chagas' disease, produces mitogenic substances responsible for the polyclonal B-cell activation observed during the acute phase of the infection. Isolation and characterization of the molecules involved in the induction of polyclonal activation observed during infectious diseases have posed a great challenge for the immunologist over the last decade. In this work we report that a 33 kD protein obtained from an alkaline fraction of T. cruzi epimastigotes (FI) stimulates proliferation and promotes differentiation into antibody-secreting cells of normal murine B cells in a T-cell independent manner. By flow cytometry we also found that the 33 kDa protein induces an increase in the expression of MHC class II and B7.2 but not B7.1 molecules on the B-cell surface. Sequencing by mass spectrometry identified the T. cruzi 33 kD protein as hypothetical oxidoreductase, a member of the aldo/ketoreductase family. In this report we demonstrate that this protein is also present in the infective bloodstream trypomastigote form of the parasite and was identified as T. cruzi mitochondrial malate dehydrogenase (mMDH) by enzyme activity and by Western blotting using a specific mMDH polyclonal antiserum. The biologic relevance of mMDH-induced polyclonal activation concerning T. cruzi infection is discussed.

Effects of Yersinia enterocolitica O:3 derivatives on B lymphocyte activation in vivo.

The potential sequelae of intestinal infection with Yersinia enterocolitica include reactive arthritis, erythema nodosum, Reiter's syndrome and other autoimmune diseases. The role of the immune response in the pathogenesis of these diseases has not been fully defined, but autoimmune manifestations may be a consequence of the increase in autoantibodies as a result of polyclonal B-cell activation induced by Yersinia. We investigated the effects of Y. enterocolitica O:3 derivatives on B lymphocyte activation in vivo. Groups of five specific pathogen free (SPF) Swiss mice were inoculated with bacterial cell extract, Yersinia outermembrane proteins (Yops) or lipopolysaccharide (LPS) obtained from Y. enterocolitica O:3 and their immunoglobulin-secreting spleen cells were detected by isotype-specific protein A plaque assay. The presence of specific anti-Yersinia antibodies and autoantibodies was determined in mouse sera by ELISA. In all experiments a marked increase in the number of secretory cells of different isotypes was observed as early as the third day after inoculation. IgG and IgM anti-Yersinia antibodies were detected in the sera of all inoculated mice, and autoantibodies against myosin in the sera of those inoculated with bacterial cell extract. The sera from animals stimulated with LPS reacted with myelin, actin and laminin, while the sera from mice inoculated with Yops reacted with myelin, thyroglobulin and cardiolipin. These results suggest that SPF Swiss mice inoculated with any one of the Y. enterocolitica derivatives tested exhibited polyclonal activation of B lymphocytes as a result of stimulation by various bacterial components and not only LPS stimulation.

Differential roles of osteopontin/Eta-1 in early and late lpr disease.

The cytokine osteopontin (Eta-1) leads to macrophage-dependent polyclonal B-cell activation and is induced early in autoimmune prone mice with the lpr mutation, suggesting a significant pathogenic role for this molecule. Indeed, C57BL/6-Fas(lpr/lpr) mice crossed with osteopontin(-/-) mice display delayed onset of polyclonal B-cell activation, as judged by serum immunoglobulin levels. In contrast, they are subject to normal onset, but late exacerbation of lymphoproliferation and evidence of kidney disease. These observations define two stages of Fas(lpr/lpr) disease with respect to osteopontin-dependent pathogenesis that should be taken into account in the design of therapeutic approaches to the clinical disease.

Antinuclear Autoantibodies in Flaky Skin ( fsn ) Mutant Mice

Mice homozygous for the flaky skin ( fsn ) single gene mutation have a severe hyperproliferative disease resulting complex phenotype, which includes widespread inflammation and autoimmunity. Flaky skin mice have several serological and pathological features that share similarities with the human systemic autoimmune disease systemic lupus erythematosus (SLE). Analyses of the antinuclear and anti-dsDNA autoantibodies in fsn / fsn mice indicate that they are low titer IgG antibodies. These low titer anti-dsDNA autoantibodies can ultimately form immune complex deposition in the glomeruli associated kidney damage. IgE antibodies were identified in the immune complex deposition, however their role in the pathology is not determined. It is hypothesized that the mechanism of autoantibody production and autoimmune disease pathogenesis in mice homozygous for the fsn mutation is initiated by non-specific polyclonal activation of B-lymphocytes resulting in the synthesis of low affinity autoantibodies.

Bacterial infections and atopic dermatitis.

Bacterial infections and atopic dermatitis.

The Effect of Dose, Gender, and non-H-2 Genes in Murine Mercury-induced Autoimmunity

We have studied the effect of dose, treatment time, gender and non-H-2 genes on immune parameters and toxicokinetics in murine mercury-induced autoimmunity (HgAI). The partly-proven mechanism for HgAI is the modification of the autoantigen fibrillarin by mercury, followed by a T cell-dependent immune response driven by the modified fibrillarin. In the H-2 congenic (H-2S) mouse strains A.SW and B10.S given203HgCl2in a dose of 0.25–8mg Hg/l drinking water for up to 10 weeks, the internal dose measured as the whole-body retention of mercury reached steady state within 5 weeks. Fifty percent of the steady state level was reached already after 2 days. Conditions therefore exist for a rapid modification of fibrillarin, followed by a T cell-dependent immune response, which is consistent with the presence of anti-fibrillarin antibodies (AFA) in serum after 2 weeks. AFA developed in a dose-dependent pattern. Serum IgE showed a dose-dependent increase with a maximum after 1–2.5 weeks followed by a distinct decline towards the baseline level. Substantial polyclonal B-cell activation (PBA) developed in the highest dose groups only. Since AFA developed using lower doses too, PBA can be excluded as a general mechanism for induction of AFA. Tissue immune-complex (IC) deposits were present in the highest dose groups only, indicating a possible causality between PBA and IC deposits. The substantially lower whole body and organ mercury level needed to induce AFA in the A.SW strain as compared with the H-2 congenic B10.S strain, demonstrates that genetic factors outside the H-2 region, and not related to toxicokinetics, modifies the autoimmune response. In contrast, the difference in mercury thresholds for induction of IgE was only slight between A.SW and B10.S mice, indicating basically different mechanisms for induction of AFA and serum IgE.