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P W Mathieson

Publications and source records attributed to P W Mathieson.

At least 55 records · Page 3Linked to original sources
PubMed1995

Compounds that induce autoimmunity in the brown Norway rat sensitize mast cells for mediator release and interleukin-4 expression.

Brown Norway (BN) rats given mercuric chloride (HgCl2), gold (Au) salts or D-penicillamine develop a T helper 2 (Th2) cell-mediated autoimmune syndrome. The recent observation of tissue injury within 24 h of HgCl2 treatment suggested the involvement of a non-T cell. We therefore examined the effect of these compounds on rat mast cells in vitro. Incubation of BN rat peritoneal mast cells with HgCl2 enhanced the release of serotonin in response to IgE cross-linking agents. Mast cells from Lewis rats, a strain not susceptible to the autoimmune syndrome in vivo, were affected to a lesser extent. The effect was observed with purified BN mast cells, suggesting a direct action. Similar effects were seen with D-penicillamine in the presence of copper ions, a combination that produces hydrogen peroxide, and Au. HgCl2 caused significant induction of interleukin (IL)-4 mRNA in mast cells from BN, but not Lewis rats. The data demonstrate a novel enhancing effect of a number of compounds on mast cell mediator release, and an inducing effect of HgCl2 on mast cell IL-4, expression. These findings are consistent with our hypotheses that mast cells may contribute to early tissue injury, and also, via production of IL-4, may initiate and/or augment, the Th2 response in the BN rat model of chemical-induced autoimmunity.

Animals↗
PubMed1995

The time course and characterization of mercuric chloride-induced immunopathology in the brown Norway rat.

Mercuric chloride (HgCl2) induces an autoimmune syndrome in the Brown Norway (BN) rat which includes widespread tissue injury. There is necrotizing leucocytoclastic vasculitis in the gut with maximal injury occurring 2 weeks after the start of HgCl2 injections. There is evidence that disease is driven by Th2-like cell (CD4+CD45RClow) activity and that Th1-like cells (CD4+CD45RChigh) may be protective. Using the established protocol of five injections of HgCl2 over 10 days, we have studied in greater detail the presence and extent of vasculitis and changes in T cell subsets from 12 h to 20 days after the first injection. Animals were killed at various time points and necropsies performed. Tissue injury was scored both macroscopically and histologically, with immunohistochemistry for T cell subsets. Flow cytometry was used to determine T cell subsets in peripheral blood, mesenteric lymph node (LN) and spleen. Tissue injury was seen as early as 24 h after the first injection of HgCl2. The size of lesions and extent of vasculitis increased over the next two weeks with partial resolution at day 20. We confirmed that of peripheral blood T cells in the BN rat, less than 20% were CD8+ and a similar proportion were CD4+CD45RChigh, but found that less than 75% of CD8+ T cells were CD45RChigh (in other strains of rat more than 90% CD8+ T cells are CD45RChigh). Within 48 h, HgCl2 caused a rise in the proportion of CD4+ T cells in spleen, LN and peripheral blood which then fell towards normal at peak tissue injury. The proportion of CD4+CD45RClow T cells rose in the first week, but subsequently fell, with reciprocal changes in CD4+CD45RChigh T cells. There was an increase in CD8+ T cells towards peak disease. The speed of onset of tissue injury suggests that cells other than T cells may be involved in the primary induction of vasculitis, although Th2-like cells may be important in further tissue injury and in B cell activation. The rise in CD8+ and Th1-like cells towards peak disease supports the hypothesis that they are involved in disease regulation.

Animals↗
PubMed1995

Interleukin-4 gene expression in mercury-induced autoimmunity.

Mercuric chloride (HgCl2) induces autoimmunity in Brown Norway (BN) rats, with necrotizing vasculitis in the gut. Circumstantial evidence implicates the Th2 subset of CD4+ T lymphocytes, which produces IL-4. We developed a quantitative polymerase chain reaction (PCR) technique to quantify IL-4 gene expression. A phagemid containing rat IL-4 cDNA was modified to act as the template for a synthetic RNA construct; a known amount of synthetic RNA was added to total RNA from spleen and caecum of BN rats at various times after HgCl2, followed by reverse transcriptase PCR. IL-4 gene expression increased markedly in spleen and caecum after HgCl2. Splenic levels peaked by 10 days at approximately five-times baseline, then returned towards normal as the autoimmune response was spontaneously regulated. Caecal IL-4 expression peaked at 48 h, at which time we observed a previously unreported early phase of tissue injury, with necrotizing vasculitis qualitatively similar to that reported previously in the later phases of the model. These data support a key role for IL-4 in this experimental model of autoimmunity. The quantitative PCR technique can be modified for analysis of other cytokines, allowing further investigation of the role of T cell subsets in this model.

Animals↗
PubMed1995

Cyclosporin A exacerbates mercuric chloride-induced vasculitis in the brown Norway rat.

BACKGROUND: Administration of mercuric chloride (HgCl2) to the Brown Norway (BN) rat induces a necrotizing leukocytoclastic vasculitis (most marked in the gut) and anti-myeloperoxidase (anti-MPO) antibodies. The development of autoimmunity in the BN rat is a T cell-dependent phenomenon, and there is evidence that the induction of autoantibodies and tissue injury is a Th2-driven process. Cyclosporin A (CyA) is an anti-T cell agent with a dose-dependent differential effect on Th cell subsets that can ameliorate or enhance autoimmune responses. In the BN it can suppress HgCl2-induced autoantibody production, but the effect on tissue injury has not been previously examined. EXPERIMENTAL DESIGN: We have studied the effect of CyA given "early" (Days 1-10, concurrently with the HgCl2) or "late" (Days 11-14) on tissue injury and autoantibody response. Serial blood samples were taken for anti-glomerular basement membrane, anti-MPO, and IgE antibody levels. Necropsies were performed on animals killed on Day 15. The presence and extent of vasculitis was scored macroscopically and histologically. Controls were incorporated to assess the effect of vehicle and of CyA alone. RESULTS: CyA given early delayed the rise in anti-MPO and anti-glomerular basement membrane levels and ameliorated tissue injury, whereas CyA given late, although suppressing the rise in anti-MPO and anti-glomerular basement membrane antibodies, caused a marked exacerbation of vasculitis. CONCLUSIONS: The effect of CyA depends on the timing of treatment with respect to HgCl2. Anti-MPO antibodies are not of primary importance in the pathogenesis of tissue injury. The late effect may be due to a direct toxic effect on the endothelium or to loss of a protective T cell subset. These observations have implications for the use of CyA in the treatment of systemic vasculitis in humans.

Animals↗
PubMed1994

Molecular analysis of C3 allotypes in Chinese patients with immunoglobulin A nephropathy.

The third component of complement (C3) exists in two main allotypic forms, C3S and C3F. An increased frequency of the rarer C3F allele has been reported in several autoimmune conditions, including immunoglobulin A nephropathy (IgAN), in white patients. C3F is known to be rare in the Chinese population, but C3 allotypes have not been studied in Chinese patients with IgAN. The molecular basis of the S/F polymorphism has been established recently: a single base change at the DNA level encodes a single amino acid substitution in the protein. A second polymorphism, closely linked to the first, is defined by the monoclonal antibody HAV 4-1, and also is due to a single base change. These polymorphisms therefore can be analyzed at the DNA level. We have used the amplification refractory mutation system, a modification of the polymerase chain reaction, to analyze these two C3 polymorphisms on genomic DNA from 133 Hong Kong Chinese individuals: 54 patients with IgAN and 79 controls. No C3F alleles were present in either group: all individuals were homozygous C3S. Twenty-six patients were also allotyped for the HAV 4-1 polymorphism; all 26 were homozygous HAV 4-1 negative, as would be predicted from the close linkage of this allotype to C3S in other populations. These data indicate that C3F is not a susceptibility allele for IgAN in Hong Kong Chinese individuals, and confirm in a large DNA-based study the rarity of C3F in this population.

Adolescent↗
PubMed1994

Effects of decomplementation with cobra venom factor on experimental vasculitis.

Mercuric chloride (HgCl2) induces autoimmunity in susceptible rat strains, with hyper-IgE, appearance of a number of autoantibodies, and widespread tissue injury, including necrotizing vasculitis in the gut. In the early phase of tissue injury there is granulocyte infiltration; later there is immunoglobulin deposition along basement membranes in vessels. We have analysed the role of complement in this model using cobra venom factor (CVF), which causes decomplementation lasting around 5 days. The characteristic time course when HgCl2 is given over 10 days is that tissue injury and autoantibody levels reach a peak at around day 15 (start of HgCl2 = day 0). We therefore gave CVF either early (day 0), intermediate (day 5) or late (day 10); a fourth group (controls) received HgCl2 but no CVF. At each time point, CVF caused complete decomplementation which lasted for at least 5 days. Serum IgE and autoantibody levels were similar in all four experimental groups. Tissue injury in the 'early' CVF group and in the 'late' CVF group was not significantly different from controls, but in the intermediate group tissue injury was significantly more severe than in controls. These data indicate that the complement system does not play a major role in the induction of autoantibodies by HgCl2, nor in the effector phase of tissue injury. We speculate that the exacerbation of tissue injury by CVF in the group given this agent at an intermediate stage of the model is explained by the presence of products of C3 activation which have proinflammatory effects during the phase of active granulocyte-mediated tissue injury.

Animals↗
PubMed1994

Use of methyl prednisolone and antioxidants in mercuric chloride-induced experimental vasculitis.

The systemic vasculitides are characterized by necrotizing inflammation of blood vessels. Neutrophils are implicated in tissue damage by their presence at the site of injury. They can mediate injury by release of cellular contents including proteinases, cytokines and reactive oxygen species. Antioxidants such as vitamin E and N-acetyl cysteine (NAC) may therefore be predicted to ameliorate oxidative damage in vivo and could be a cheap and non-toxic form of therapy. We examined this hypothesis in an experimental model of vasculitis which has some similarities to human disease, and in which depletion of neutrophils ameliorates tissue injury. Mercuric chloride (HgCl2) treatment induces an autoimmune syndrome and necrotizing leucocytoclastic vasculitis in the Brown Norway (BN) rat; anti-myeloperoxidase (MPO) and anti-glomerular basement (GBM) antibodies are present, and vasculitis is reduced by antimicrobials. Methyl prednisolone given intravenously was effective in reducing tissue injury, demonstrating that the model was responsive to a treatment used in man. Vitamin E and NAC were given as daily injections intraperitoneally to BN rats either before, during or after HgCl2 administration. Serial blood samples were taken for anti-MPO and IgE antibodies, which were assayed by ELISA. Necropsies were performed on animals killed at peak disease. At doses of 50-200 mg/kg per day vitamin E had no beneficial effect on tissue injury, regardless of timing of treatment. NAC at 100 or 200 mg/kg also had no significant protective effect on vasculitis. Autoantibody and IgE levels were not affected by either methyl prednisolone or the antioxidants. The lack of benefit of vitamin E and NAC suggests that oxidative damage, whether generated by neutrophils or other cells, does not play a major role in the pathogenesis of vasculitis, and that antioxidant therapy is unlikely to be of benefit in systemic vasculitis in man.

Acetylcysteine↗
PubMed1994

Molecular analysis of C3 allotypes in patients with systemic vasculitis.

The third component of complement (C3) exists in two main allotypic forms, C3S and C3F, distinguished at the DNA level by a single base change. An increased frequency of the rarer C3F allele has been reported in patients with the autoantibody nephritic factor and in several other autoimmune conditions such as rheumatoid arthritis and IgA nephropathy. Studies of the immunogenetic factors predisposing to the development of systemic vasculitis have produced conflicting results and no major genetic predisposing factors have been identified. We have studied the C3S/F polymorphism in 63 patients with systemic vasculitis using DNA allotyping by the amplification refractory mutation system, a modification of the polymerase chain reaction. The allele frequency in these patients was C3S 0.71, C3F 0.29 (expected C3S 0.8, C3F 0.19; chi-squared = 5.1, P < 0.025), with the average relative risk for the development of systemic vasculitis associated with the presence of a C3F allele being 2.6. Moreover, there was a marked excess of C3FF homozygotes (11/63, [17.5%], versus 4% expected: chi-squared = 9.5, p < 0.01). The average relative risk for the development of systemic vasculitis in C3F homozygotes was 5.1, indicating a gene dosage effect. These data indicate that the C3F allele is associated with a predisposition to the development of systemic vasculitis and that C3F homozygotes are at particularly high risk. This association is the strongest genetic factor reported so far for this group of diseases.

Alleles↗
PubMed1993

Complement-mediated adipocyte lysis by nephritic factor sera.

Recent data indicate a previously unsuspected link between the complement system and adipocyte biology. Murine adipocytes produce key components of the alternative pathway of complement and are able to activate this pathway. This suggested to us an explanation for adipose tissue loss in partial lipodystrophy, a rare human condition usually associated with the immunoglobulin G(IgG) autoantibody nephritic factor (NeF) which leads to enhanced alternative pathway activation in vivo. We hypothesized that in the presence of NeF, there is dysregulated complement activation at the membrane of the adipocyte, leading to adipocyte lysis. Here we show that adipocytes explanted from rat epididymal fat pads are lysed by NeF-containing sera but not by control sera. A similar pattern is seen with IgG fractions of these sera. Adipocyte lysis in the presence of NeF is associated with the generation of fluid-phase terminal complement complexes, the level of which correlates closely with the level of lactate dehydrogenase, a marker of cell lysis. Lysis is abolished by ethylenediaminetetraacetic acid, which chelates divalent cations and prevents complement activation, and reduced by an antibody to factor D, a key component of the alternative pathway. These data provide an explanation for the previously obscure link between NeF and fat cell damage.

Adipose Tissue↗
PubMed1993

Regulatory role of OX22high T cells in mercury-induced autoimmunity in the brown Norway rat.

The monoclonal antibody OX22 defines a functional split within CD4+ T cells in the rat, with OX22high cells mainly producing interleukin 2 (IL-2) and interferon gamma and responsible for delayed-type hypersensitivity responses, and OX22low cells mainly producing IL-4 and -5 and responsible for providing B cell help. There are reciprocal interactions between OX22high and OX22low cells, and it has been suggested that the OX22low subset has a role in the prevention of autoimmunity. We have used OX22 in vivo to define the role of these subsets in mercuric chloride-induced autoimmunity in the Brown Norway rat. In this model, there is polyclonal B cell activation and animals develop widespread tissue injury. Treatment of thymectomized animals with OX22 led to a profound reduction in the number of OX22high T cells in the peripheral blood. OX22-treated animals consistently developed more severe tissue injury than controls given an irrelevant antibody of the same isotype. Control animals pretreated with broad spectrum antimicrobial drugs showed milder tissue injury, but this protective effect of antimicrobials was lost in OX22-treated animals. Transfer of naive T cells to OX22-treated animals provided protection, but if T cells were depleted in vitro of OX22high cells before transfer, this effect was lost. These data provide evidence for a protective immunoregulatory role for OX22high T cells in mercuric chloride-induced autoimmunity.

Animals↗
PubMed1993

Animal models of systemic vasculitis.

Necrotizing leucocytoclastic vasculitis is the histopathological hallmark of the small vessel systemic vasculitides (SV), a group of human diseases commonly associated with anti-neutrophil cytoplasm autoantibodies (ANCA). Necrotizing vasculitis is seen in a number of experimental systems, but none of these provide an ideal animal model for human SV. Vasculitis occurs in serum sickness reactions; in murine models of systemic lupus erythematosus; in association with infection, particularly chronic viral infections; and after treatment with certain drugs or inflammatory mediators. 'Spontaneous' vasculitis has been reported in specific mouse strains, especially with ageing, and in some larger species. The size of vessel involved and the type of inflammatory cells predominating are variable in these experimental situations, and none of these models feature antibodies analogous to ANCA. We have recently reported that Brown Norway rats treated with mercuric chloride (HgCl2) develop necrotizing leucocytoclastic vasculitis, especially in the gut, and also develop antibodies to myeloperoxidase (MPO) which recognize similar determinants on MPO to those bound by a subset of ANCA. Transfer of serum from HgCl2-treated rats to naive animals does not induce tissue injury. Preliminary experiments using pooled immunoglobulin or an anti-CD4 monoclonal antibody did not show useful therapeutic benefit from these treatments. HgCl2-induced vasculitis has weaknesses as an animal model of human SV, but is the only experimental model in which anti-MPO autoantibodies have so far been demonstrated, and therefore may be of particular relevance to ANCA-associated SV.

Animals↗
PubMed1993

Further characterization of an animal model of systemic vasculitis.

The demonstration of vasculitis and anti-myeloperoxidase antibodies in the mercuric chloride treated Brown Norway rat provides a useful, though limited, animal model of systemic vasculitis. We describe some preliminary experiments on the effect of transfer of serum from mercuric chloride treated rats and of two forms of immunotherapy: intravenous immunoglobulin and an anti-CD4 antibody. Transfer of serum did not lead to tissue injury and neither of the two forms of therapy proved beneficial in this model.

Animals↗
PubMed1993

Molecular analysis of C3 allotypes in patients with nephritic factor.

The autoantibody nephritic factor (NeF) leads to complement consumption in vivo and is associated with type II mesangiocapillary glomerulonephritis (MCGN II) and partial lipodystrophy (PLD). The third component of complement (C3) exists in two common allotypic forms, C3S and C3F, distinguished at the protein level by electrophoresis. An increased frequency of the rarer C3F allele has been reported in several autoimmune conditions, including one small series of patients with NeF. However, patients with NeF have low levels of circulating C3 so that allotyping at the protein level is difficult. The molecular basis of the S/F polymorphism has recently been established: a single base change at the DNA level encodes a single amino acid substitution at the protein level. A second polymorphism, closely linked to the first, is defined by the MoAb HAV 4-1, and is also due to a single base change. These polymorphisms can therefore be analysed at the DNA level. We have used the amplification refractory mutation system (ARMS), a modification of the polymerase chain reaction (PCR), to analyse these two C3 polymorphisms at the DNA level in 26 patients with NeF. The allele frequencies of C3S and C3F were 0.673 and 0.327 (predicted values 0.79 and 0.2, chi 2 = 4.813, P < 0.05), giving a relative risk of 2.1 for the development of NeF conferred by the presence of a C3F allele. The HAV 4-1 allele frequencies were (-) 0.71 and (+) 0.29, i.e. not significantly different than predicted from the linked C3S/F allele frequencies. This is the largest series of patients with NeF yet published, and our data confirm an association between C3F and NeF. Possible mechanisms for for this link are discussed.

Adolescent↗