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D B Oliveira

Publications and source records attributed to D B Oliveira.

At least 19 recordsLinked to original sources
PubMed1992

T and B cell responses to neutrophil cytoplasmic antigens in systemic vasculitis.

The systemic vasculitides (SV) are characterized by the presence of autoantibodies to neutrophil cytoplasmic antigens (ANCA). The role of T cells in SV is uncertain. We studied human and murine T cell responses to human neutrophil cytoplasmic antigens in vitro. T cells from mice immunized with the neutrophil extract showed dose-dependent antigen-specific proliferation, restricted by the MHC class II E molecule. Myeloperoxidase (MPO) was not an important target antigen for murine T cells. Peripheral blood lymphocytes (PBLs) were obtained from 36 patients with SV, 31 before the start of immunosuppressive therapy, and from 11 healthy controls. T cell responses to the neutrophil extract in vitro did not differ between patients and controls: there were only low levels of antigen-specific proliferation, and this could not be amplified by in vitro selection. In 3 patients and 2 normals, PBLs were also tested after the depletion of CD8+ cells; this did not unmask T cell reactivity to neutrophil extract. The lack of demonstrable T cell reactivity to this antigen preparation may indicate that T cells do not play an important effector role in these diseases. A solid-phase spot ELISA was adapted to demonstrate autoantibody-producing B cells in vitro. Low numbers of ANCA-producing B cells could be demonstrated in the majority of patients. B cells producing antibody to MPO could be demonstrated in most patients and in three laboratory staff, but not in normals from outside the laboratory. In 2 patients, sequential B cell spot ELISAs were performed during the introduction of therapy, and autoantibody-producing B cells rapidly decreased in number. This assay may therefore be useful in monitoring the effects of treatment at the cellular level.

Animals↗
PubMed1992

Anti-mitochondrial antibody IgG subclass distribution and affinity in primary biliary cirrhosis.

We have studied the total IgG subclass and anti-mitochondrial antibody (AMA) specific IgG subclass distribution in primary biliary cirrhosis (PBC) sera. In order to solve the problems caused by the differing affinities of subclass specific monoclonals and the competitive inhibition of antibodies in a whole serum assay, six sera were separated into subclass-specific fractions by affinity-depletion chromatography. AMA subclass distribution of 20 further sera from patients with PBC was assessed using conventional methods and the results were calibrated against one of the fractionated sera. Light chain distribution and AMA functional affinity were also assessed for the fractionated subclasses. Total amounts of IgG3 were significantly increased compared with normal controls. AMA were found in all IgG subclasses and not restricted predominantly to IgG3 as previously described. The functional affinity of IgG3 AMA is generally lower as compared with that of other subclasses. No light chain restriction was found.

Animals↗
PubMed1992

Autoantibodies to myeloperoxidase in brown Norway rats treated with mercuric chloride.

BACKGROUND: Mercuric chloride (HgCl2) induces an autoimmune syndrome in Brown Norway (BN) rats characterized by the presence of a number of autoantibodies, including antibodies to glomerular basement membrane. Tissue injury has previously been reported to be rare in this model, but in the accompanying paper we describe changes in a number of organs including a necrotizing leucocytoclastic vasculitis in the gut. Myeloperoxidase (MPO) is one of the target antigens for anti-neutrophil cytoplasm antibodies, that are present in the majority of patients with the human autoimmune disease systemic vasculitis and have been implicated in pathogenesis. There is at present, no animal model for anti-neutrophil cytoplasm antibody positive systemic vasculitis. EXPERIMENTAL DESIGN: Ten BN rats were given five injections of HgCl2, each of 1 mg/kg, over 10 days. Sequential serum samples were tested for autoantibodies to MPO using solid phase assays, indirect immunofluorescence on normal rat neutrophils, and Western blot analysis. The specificity of these antibodies in the solid phase assay was confirmed by inhibition studies with purified antigen, and by testing binding to uncoated plates. Sera from control animals treated with saline were also tested. RESULTS: BN rats given HgCl2 developed antibodies to MPO, which in Western blots bound to similar determinants to those bound by human anti-MPO antibodies. The anti-MPO antibodies resolved spontaneously, with a time course similar to that of the anti-glomerular basement membrane antibodies, but there was no correlation between the two antibody responses in individual animals. There was no anti-MPO activity in sera taken before HgCl2 was given, nor in sera from saline-treated controls. CONCLUSIONS: BN rats treated with HgCl2 develop anti-MPO antibodies. Together with the description in the accompanying paper of necrotizing vasculitis in these animals, these observations suggest that HgCl2-induced autoimmunity in the BN rat may provide a useful model of anti-neutrophil cytoplasm antibody positive systemic vasculitis.

Animals↗
PubMed1992

Mercuric chloride-treated brown Norway rats develop widespread tissue injury including necrotizing vasculitis.

BACKGROUND: Mercuric chloride (HgCl2) induces a T cell-dependent autoimmune syndrome in Brown Norway (BN) rats, characterized by polyclonal B cell activation and circulating autoreactive T cells. A number of autoantibodies are produced, including antibodies to glomerular basement membrane, and there are circulating immune complexes. However, histologic evidence of tissue injury in this model has previously been reported to be rare. EXPERIMENTAL DESIGN: Six BN rats were given five injections of HgCl2, each of 1 mg/kg, over 10 days. Controls were four BN rats given equal volumes of saline and 10 Lewis rats given the same amount of HgCl2. Blood samples were taken thrice weekly. Animals were killed at various stages, necropsies performed, and organs histologically examined. The effect of pretreatment with broad spectrum antimicrobial drugs was examined by comparing two further groups of six BN rats: one group was pretreated with tylosin, ivermectin, and metronidazole before HgCl2 was given, and the other group received no pre-treatment. RESULTS: HgCl2-treated BN rats developed inflammation and ulceration of the skin which was most marked at mucocutaneous junctions. Macroscopic examination of internal organs showed hepatomegaly and gross haemorrhagic lesions in the wall of the gut, most marked in the duodenum and caecum. Microscopically, the skin lesions were characterized by a subepidermal mononuclear cell infiltrate with occasional hair shaft necrosis. In the liver there was a periportal mononuclear cell infiltrate, and in the gut there was intense submucosal inflammation and a leucocytoclastic vasculitis accompanied in places by mucosal ulceration. Lewis rats (which are not prone to mercury-induced autoimmunity) showed no such changes after receiving HgCl2, nor did control BN rats given saline. BN rats pretreated with broad spectrum antimicrobial agents and then given HgCl2 showed milder histologic abnormalities, although antimicrobial treatment did not affect the antiglomerular basement membrane autoantibody response. CONCLUSIONS: We have identified a syndrome induced by mercuric chloride in BN rats in which there is evidence of tissue injury in many organs, with some features in common with graft-versus-host disease. There is also necrotizing leucocytoclastic vasculitis affecting the gut, and the importance of this is enhanced by the description in the accompanying paper of autoantibodies similar to those found in human systemic vasculitis. Our observations strengthen the analogies between this model and human autoimmune disease.

Animals↗
PubMed1991

Sequences of the mouse F protein alleles and identification of a T cell epitope.

F protein is found predominantly in the liver and is of unknown function. The protein has been of interest to immunologists in the areas of self tolerance and the immunogenetics of the anti-F protein response. In the mouse there are two alleles (F1 and F2), and although mice are completely tolerant to the self form of the protein, mice of responder strains make a good antibody response to immunization with the non-self form. This response cross-reacts with the self form, implying firstly, that autoreactive B cells are present and that tolerance is therefore maintained at the T cell level, and secondly, that the difference between the two allelic products defines a T cell epitope. Primers based on the published sequence for rat F protein were used in the polymerase chain reaction to amplify the cDNA for the two mouse alleles. Subsequent sequencing shows a high degree of sequence identity between the rat and mouse cDNA. The two mouse cDNA are identical apart from a single A to G base change which predicts an asparagine (F1 protein) to aspartate (F2 protein) amino acid residue change. Using allele-specific oligonucleotide probes we confirmed that this base change has the same strain distribution as the previously determined F protein type. Isoelectric focusing shows that F1 protein migrates in a more basic position than F2 protein, as predicted by the asparagine to aspartate change. Finally, a synthetic peptide from the allovariable site of F2 protein will successfully restimulate T cells in vitro from an F1 type mouse primed in vivo with whole F2 protein, whereas the corresponding peptide from F1 protein will not. This is evidence that, as predicted, the allovariable site does indeed define a T cell epitope. Peptides covering the rest of the F2 protein molecule were not stimulatory.

Alleles↗
PubMed1991

Immunoregulation of mercuric chloride-induced autoimmunity in Brown Norway rats: a role for CD8+ T cells revealed by in vivo depletion studies.

Mercuric chloride (HgCl2) induces the production of autoantibodies to glomerular basement membrane (GBM) in the Brown Norway (BN) rat. The autoimmune response is self-limiting and thereafter the animals are resistant to rechallenge with HgCl2. Resistance can be transferred to naive animals by spleen cells from HgCl2-treated rats. A similar state of resistance can be induced with a low dose of HgCl2, insufficient in itself to induce autoimmunity. We have examined the role of CD8+ T cells in the immunoregulation of this experimental model by depleting this subset in vivo. We have also used inhibition studies in a solid-phase radioimmunoassay in an attempt to demonstrate any effect of anti-idiotypic antibodies in the spontaneous resolution of the anti-GBM antibody response. The initial induction and spontaneous resolution of anti-GBM antibodies were unaffected by depletion of CD8+ T cells. However, CD8-depleted animals were no longer resistant to rechallenge with HgCl2. Cell transfer studies showed that spleen cells from CD8-depleted animals conferred less resistance to HgCl2 than those from animals which had received control antibody. CD8 depletion also reduced the resistance induced by pretreatment with low-dose HgCl2. Studies in which peak sera were pre-incubated with post-recovery sera before testing in a solid-phase anti-GBM radioimmunoassay did not support an important role for anti-idiotypic antibodies. We conclude that CD8+ T cells play an important role in the resistance to rechallenge with HgCl2 in the BN rat, although they are not required for the induction or spontaneous resolution of the initial autoimmune response. Demonstration of the reversal of a suppressive phenomenon in vivo using an anti-CD8 monoclonal antibody is unusual.

Analysis of Variance↗
PubMed1991

Effects of ancrod and rtPA on fibrin accumulation, glomerular inflammation and renal function in nephrotoxic nephritis.

We have compared the effects of ancrod and recombinant tissue plasminogen activator (rtPA) on nephrotoxic nephritis induced in pre-immunized rabbits by the administration of nephrotoxic globulin (NTG; sheep anti-rabbit glomerular basement membrane). We used three different doses of NTG: in each experiment three groups of six rabbits were preimmunized with normal sheep globulin and given NTG: group A received no further treatment; group B received rtPA, 2 mg/kg 12 hourly; group C received ancrod 2 U/kg 12 hourly. Animals were bled daily for estimation of plasma fibrinogen and serum creatinine, then killed on day 5 and kidneys removed for histology. 1 ml/kg of NTG caused massive glomerular necrosis, all three groups having severe renal failure. With 0.5 ml/kg of NTG, ancrod and rtPA both effectively prevented fibrin deposition in Bowman's space, but all animals had severe proliferative glomerulonephritis and marked renal failure. With 0.25 ml/kg of NTG, control animals developed severe proliferative nephritis and advanced renal failure, ancrod provided almost complete protection, and the rtPA group had renal injury and functional impairment intermediate between the other two groups. We conclude that renal failure in severe nephrotoxic nephritis is fibrin-independent, but in less fulminant nephritis renal function can be protected by defibrination with ancrod. rtPA is capable of reducing glomerular fibrin accumulation as effectively as ancrod, but provides inferior protection of renal function.

Ancrod↗
PubMed1991

Liver damage in long-term anticonvulsant therapy: a serological and histological study.

The prevalence of liver damage in patients receiving long-term anticonvulsant therapy was determined, using a new marker of liver disease, the serum F protein concentration. Abnormal serum F protein concentrations were detected in 50 per cent of 34 patients receiving anticonvulsant therapy. A retrospective analysis of post-mortem liver samples showed common histological abnormalities in three out of seven patients who had died whilst receiving anticonvulsant therapy. These changes were not seen in control patients. We suggest that chronic anticonvulsant therapy may cause significant hepatocellular damage.

Adult↗
PubMed1990

Autoimmunity and the pathogenesis of glomerulonephritis.

Self-tolerance is maintained by: thymic influences on developing T cells; peripheral mechanisms that can tolerise post-thymic T cells; and to a variable extent the tolerisation of potentially autoreactive B cells. The presence of autoreactive T cells in normal individuals suggests that mechanisms to control the activity of such cells may be important. Failure of any of these processes may lead to autoimmunity. The relationship between glomerulonephritis and the mechanisms leading to breakdown of self-tolerance remains elusive. An important observation is that autoimmune diseases are strongly associated with particular products of the major histocompatibility complex (MHC). This association may reflect the intimate involvement of the MHC in thymic T cell education. Another explanation is that T cells only recognise antigens presented in the context of MHC molecules. Although there has been progress in identifying the targets recognised by autoantibodies in vasculitis and anti-GBM disease, nothing is known about the T cells involved. Despite our ignorance, therapy aimed specifically at the T cell can be effective. This approach is being supplemented by attempts to engage immunoregulatory mechanisms, such as idiotype-antiidiotype interactions. The hope is that such treatments, or combinations thereof, will allow a more focused suppression of the autoimmune response, in contrast to the non-specific (and therefore potentially dangerous) methods of immunosuppression available at present.

Autoantigens↗