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Biomedical subjects

H H Peter

Publications and source records attributed to H H Peter.

At least 91 records · Page 5Linked to original sources
PubMed1997

Transcription factor Egr-1 activity down-regulates Fas and CD23 expression in B cells.

Activation of mature B cells via Ag receptor cross-linking induces transient expression of the transcription factor Egr-1. Although the activating signals leading to Egr-1 induction have been studied extensively, little is known about the genes that are placed further downstream within this activation cascade and that are transcriptionally regulated by Egr-1. To identify such target genes, we established Egr-1-overexpressing transfectants from the murine B cell line K46 and from human Ramos B cells. All clones derived from K46 B cells showed increased expression of CD44. Most interestingly, expression of CD95 (Fas/Apo-1) and of CD23 was down-regulated in all K46 transfectants. As a consequence, they became resistant to apoptosis induced by anti-CD95 Ab treatment. Similarly, the Egr-1-expressing Ramos cells showed reduced levels of CD95 expression. Thus, Egr-1 seems to control the expression of downstream target genes not only as a transcriptional activator, but also as a repressor molecule. In B cells, Egr-1 therefore plays a critical role in integrating the short-lived signal delivered by triggering of the Ag receptor into phenotypic changes, including repression of CD95 and CD23 transcription.

Apoptosis↗
PubMed1997

The matrix metalloproteinase RASI-1 is expressed in synovial blood vessels of a rheumatoid arthritis patient.

RASI-1 is a novel matrix metalloproteinase which we isolated from an expression cDNA library representing the mRNA of an inflamed synovium obtained from a patient with rheumatoid arthritis (RA). To investigate the involvement of RASI-1 in the pathology of RA, we examined synovial specimens from RA patients with antibodies directed against an unique RASI-1-derived peptide. In comparison to interstitial collagenase, gelatinase A and B, and stromelysin 1, the RASI-1 expression in the RA-synovium is located mainly in the tunica media of blood vessel walls and its synovial localization is not as ubiquitous as that of other MMPs. The tissue inhibitor of metalloproteinases (TIMP-1), although also widely expressed in the synovium, exhibits strong colocalization with RASI-1 in blood vessel walls. While RASI-1 is expressed in blood vessels of the inflamed synovium of an RA patient, its expression was not found in control synovial specimens from patients with luxation and arthrosis. However, RASI-1 expression can also be found in non-inflamed blood vessels of uterine ligaments and skin. RASI-1, although its function and substrates are unknown, could be involved in processes such as neovascularization and angiogenesis or lymphocyte extravasation and thus may participate in joint tissue destruction during RA.

Amino Acid Sequence↗
PubMed1997

Characteristic epitope recognition pattern of autoantibodies against eukaryotic ribosomal protein L7 in systemic autoimmune diseases.

OBJECTIVE: To define the epitope-recognition pattern and the fine specificity of the autoantibody response to protein L7 in patients with rheumatic diseases. METHODS: The epitope-recognition pattern was studied by enzyme-linked immunosorbent assay utilizing overlapping fragments of L7. The fine specificity was examined by binding inhibition and isoelectric focusing. RESULTS: We observed a disease-specific epitope-recognition pattern of anti-L7 autoantibodies. There was one immunodominant epitope that was recognized by all anti-L7-positive sera from patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and systemic sclerosis (SSc). Additional recognition of minor epitopes was observed; it arises by intramolecular epitope spreading and was correlated with disease activity in SLE patients. SSc patients differed from SLE and RA patients in that their sera did not recognize certain minor epitopes. The major epitope was recognized by high-affinity autoantibodies of limited heterogeneity. Minor epitopes were recognized by heterogeneous low-affinity autoantibodies. CONCLUSION: The anti-L7 autoantibody response is oligoclonal. Additional B cell clones are activated by antigen during active phases of disease.

Adolescent↗
PubMed1997

The B cell repertoire of patients with rheumatoid arthritis. II. Increased frequencies of IgG+ and IgA+ B cells specific for mycobacterial heat-shock protein 60 or human type II collagen in synovial fluid and tissue.

OBJECTIVE: A qualitative and quantitative analysis of the functional, antigen-specific B cell receptor repertoire of patients with rheumatoid arthritis (RA) in synovial and peripheral compartments. METHODS: B cells were activated to grow and differentiate at high efficiency in vitro under limiting-dilution conditions. Isotype and specificity of the secreted Ig were tested by enzyme-linked immunosorbent assay. RESULTS: In contrast to peripheral B cells, most synovial B cells had already switched to IgG/IgA in vivo. The frequencies of B cells specifically recognizing foreign antigens were decreased within the synovial population, whereas the frequencies of B cells specific for type II collagen, mycobacterial heat-shock protein 60 (hsp60), or IgG Fc fragments were significantly increased, revealing a negative correlation in terms of frequencies. CONCLUSION: B cells specific for human type II collagen, hsp60, and IgG Fc fragments are produced and/or expanded locally within the affected joints of RA patients. Thus, the specific immune system is definitely involved in the local inflammatory and destructive processes.

Adult↗
PubMed1997

Brain glucose utilization in systemic lupus erythematosus with neuropsychiatric symptoms: a controlled positron emission tomography study.

In contrast to morphological imaging [such as magnetic resonance imaging (MRI) or computed tomography], functional imaging may be of advantage in the detection of brain abnormalities in cases of neuropsychiatric systemic lupus erythematosus (SLE). Therefore, we studied 13 patients (aged 40+/-14 years, 11 female, 2 male) with neuropsychiatric SLE who met four of the American Rheumatism Association criteria for the classification of SLE. Ten clinically and neurologically healthy volunteers served as controls (aged 40+/-12 years, 5 female, 5 male). Both groups were investigated using fluorine-18-labelled fluorodeoxyglucose brain positron emission tomography (PET) and cranial MRI. The normal controls and 11 of the 13 patients showed normal MRI scans. However, PET scan was abnormal in all 13 SLE patients. Significant group-to-group differences in the glucose metabolic index (GMI=region of interest uptake/global uptake at the level of the basal ganglia and thalamus) were found in the parieto-occipital region on both sides: the GMI of the parieto-occipital region on the right side was 0.922+/-0.045 in patients and 1.066+/-0.081 in controls (P<<0.0001, Mann Whitney U test), while on the left side it was 0.892+/-0.060 in patients and 1. 034+/-0.051 in controls (P=0.0002). Parieto-occipital hypometabolism is a conspicuous finding in mainly MRI-negative neuropsychiatric SLE. As the parieto-occipital region is located at the boundary of blood supply of all three major arteries, it could be the most vulnerable zone of the cerebrum and may be affected at an early stage of the cerebrovascular disease.

Adult↗
PubMed1997

Characterization of SV40T antigen immortalized human synovial fibroblasts: maintained expression patterns of EGR-1, HLA-DR and some surface receptors.

In rheumatoid arthritis (RA) synovial fibroblasts are activated by growth factors and cytokines to proliferate and to express matrix-degrading proteases and pro-inflammatory cytokines. This contributes to cartilage degradation and joint destruction. To analyse the parameters that lead to activation of synovial fibroblasts, we established a stable human synoviocyte line (K4IM) from a healthy donor by immortalization with SV40 T antigen (TAg). Characterizing the phenotype of the immortalized K4IM cells, we found that they maintained CD44, CD54 (intercellular adhesion molecule; ICAM-1) and CD95 (Fas) expression, but lost the expression of CD106 (vascular cell adhesion molecule 1; VCAM-1) and the receptors for interleukin 1 (IL-1) and platelet-derived growth factor (PDGF). We also monitored normal expression kinetics of transcription factor Egr-1 upon activation with tumor necrosis factor alpha (TNF-alpha) or synovial fluid from RA patients. In addition, we showed that HLA-DR expression could still be upregulated by recombinant interferon gamma (rINF-gamma). The immortalized K4IM cell line therefore represents a valuable and unique tool to study mechanisms that induce or maintain synoviocyte activation.

Antigens, Viral, Tumor↗
PubMed1997

Measurement of transcription factor c-fos and EGR-1 mRNA transcription levels in synovial tissue by quantitative RT-PCR.

The transcription factors Fos and EGR-1 are known to be involved in the regulation of the transcription of metalloproteinases and their specific inhibitors. Since the overexpression of metalloproteinases is responsible for the matrix degradation in rheumatoid arthritis (RA), exact analysis of transcription levels of c-fos and EGR-1 ex vivo may serve to monitor progression or remission of the disease activity in RA. Here we report on a method based on a quantitative reverse transcription polymerase chain reaction (RT-PCR) for rapid estimation of the transcription levels of the immediate early genes c-fos and EGR-1. Coamplification with suitable internal standards, easily generated by the use of hybrid primers, allows us to semiquantitatively measure c-fos and EGR-1 induction levels in low numbers of cultured cells or very small tissue samples obtained by synovial biopsy. The sensitivity of the method was 3.5 pg/ml for c-fos- and 10 pg/ml for EGR-1-specific cDNAs.

Arthritis, Rheumatoid↗
PubMed1997

Analysis of the human CD21 transcription unit reveals differential splicing of exon 11 in mature transcripts and excludes alternative splicing as the mechanism causing solubilization of CD21.

CD21 is found in a soluble form at low levels in normal human sera and at elevated levels in sera from patients with EBV-associated diseases and B-CLL. Ablation of complement, injection of recombinant soluble CD21 and knock-out of CD21 in mice by gene targeting interfere with T-cell-dependent immune responses, suggesting that in vivo-generated soluble CD21 may exert immunoregulatory functions. Soluble CD21 has a molecular weight of 130,000/135,000, which is equivalent to the entire extracellular domain. Soluble forms of membrane-anchored molecules may be generated by proteolytic cleavage of the extracellular portion or by the exclusion of the hydrophobic transmembrane region via alternative splicing. To delineate whether alternative splicing of CD21 mRNA creates transcripts encoding for the soluble form of CD21 we analyzed by PCR CD21 expression in PBLs, spleen, tonsils, bone marrow and in various cell lines. We found that all CD21 mRNA species contained the transmembrane exons, thus excluding alternative splicing as a factor contributing to the serum pool of soluble CD21. Differential splicing of the CD21 transcription unit has also been suggested for exon 11. Within the CD21 gene exons 3, 7 and 11 have a high degree of homology. However, we found in malignant human cell lines and primary lymphocytes from blood, bone marrow, tonsils and spleen that exon 11, but not exon 3 or 7, is subject to alternative splicing. We cloned and sequenced the intron preceding exon 11 and found that the surrounding splice sites match consensus splice sites. In conclusion, we show that human CD21 exon 11 is alternatively spliced in malignant cell lines of lymphoid origin and in purified lymphocytes from blood, tonsils, bone marrow and spleen. We found that both exon 11 lacking and exon 11 containing transcripts are always coexpressed and the ratio of the two forms is > 1. Moreover, we exclude the possibility that alternative splicing of the transmembrane region is the mechanism leading to soluble CD21.

Alternative Splicing↗
PubMed1997

Reactivity patterns of synovial T-cell lines derived from a patient with rheumatoid arthritis. I. Reactions with defined antigens and auto-antigens suggest the existence of multireactive T-cell clones.

The functional T-cell repertoire in the inflamed joint of a patient with rheumatoid arthritis was analysed at the clonal level. Using limiting dilution techniques and selecting for growth of in vivo activated and/or autoreactive T cells, 149 T-cell lines were established. They were tested in a proliferation assay for reactivity against an autologous Epstein-Barr virus (EBV)-transformed B-cell line and a panel of auto-antigens and foreign antigens. Seventy-five lines (approximately 50%) could be stimulated. Thirty-six lines (approximately 24%) were antigen-reactive. They were stimulated by human collagens type I (15), II (10), IV (7) or V (4), cartilage proteoglycans (4), Mycobacterium tuberculosis (15), the 60 kDa heat-shock protein of M. bovis (13) or tetanus toxoid (10). T-cell lines were either monoreactive (19), bireactive (6), or multireactive (11), i.e. they were stimulated by either one, by two, or by more antigens in the panel. About half of the antigen-reactive lines were at the same time autoreactive towards the autologous B-cell line. These data suggest the existence of multispecific autoreactive T-cell receptors comparable to multireactive or natural autoantibodies and prove the presence of autoantigen-reactive T cells in the inflamed joints of patients with rheumatoid arthritis.

Antigens↗
PubMed1997

A double-blind, placebo-controlled, crossover therapy study with natural human IL-2 (nhuIL-2) in combination with regular intravenous gammaglobulin (IVIG) infusions in 10 patients with common variable immunodeficiency (CVID).

Ten CVID patients with defective IL-2 synthesis in vitro were treated with nhuIL-2 in a placebo-controlled, double blind, crossover therapy study during a period of 12 months. No severe side-effects of nhuIL-2 were recorded. Marginal serum nhuIL-2 levels were measurable in individual patients only during the therapy phase. Serum levels of soluble IL-2 receptors were unaffected by the therapy. nhuIL-2 and placebo groups did not differ significantly with respect to requirement of IVIG substitutions which were performed whenever serum IgG levels dropped below 5 g/l: a total of 53 IVIG infusions (corresponding to 17.6 g IgG/month per patient) was necessary during the placebo phase, and 48 infusions (16.4 g IgG/month per patient) during the nhuIL-2 treatment phase. Thus, nhuIL-2 therapy was ineffective in improving spontaneous IgG synthesis in vivo. Nevertheless, the group of patients receiving nhuIL-2 during the first 6 months of the study exhibited a significant reduction of severe infections (n = 25) during the following 6 months of placebo treatment (n = 7) (P<0.045). The infection score dropped in this group from 181 to 23 (P<0.015). Patients of the second group receiving first placebo and then nhuIL-2 did not experience a significant difference in number and score of infectious episodes: 25 infections were recorded during the first 6 months and 24 during the following 6 months. We suppose that nhuIL-2 therapy of CVID patients reduces susceptibility to severe infections, possibly via the induction of a specific antibody response, which is effective at the earliest 6 months after initiating nhuIL-2 therapy.

Adult↗
PubMed1997

Transient CD80 expression defect in a patient with variable immunodeficiency and cyclic neutropenia.

CD80 expression on stimulated B cells of 9 common variable immunodeficiency (CVID) patients and 10 healthy control individuals was examined. Here we report on an exceptional CVID patient with recurrent episodes of cyclic neutropenia, skin vasculitis and recurrent infections associated with a transient, but reproducible CD80 expression defect on stimulated B cells. Concomitantly serum Ig levels were markedly reduced and B cell counts were low. Interestingly, after recovery from an episode of neutropenia and vasculitis we observed an improvement of the CD80 expression as well as an increase in the number of B cells and a recovery of IgM and IgG production in vivo and in vitro.

B-Lymphocytes↗
PubMed1997

Lactose-intolerance may induce severe chronic eczema.

The primary acquired lactase deficiency of the adult is known to cause various disturbances in the gastrointestinal tract while extraintestinal symptoms are unusual. Here we report on a histologically proven chronic eczema requiring corticosteroid treatment for several months. It was obviously induced by a concomitant lactose intolerance since the introduction of a lactose-free diet led to a complete disappearance of the eczema and allowed the discontinuation of the corticosteroid treatment. As far as we know, this is the first case report of an eczema caused by a lactose intolerance.

Adrenal Cortex Hormones↗
PubMed1997

Elevated anticardiolipin antibodies in autoimmune haemolytic anaemia irrespective of underlying systemic lupus erythematosus.

In patients with systemic lupus erythematosus (SLE) and concomitant Coombs positive autoimmune haemolytic anaemia (AIHA) anticardiolipin antibodies (aCL) are found more frequently and at higher titres than in SLE patients without AIHA. In order to assess if aCL elevation is primarily associated with the underlying SLE, or with AIHA itself, we examined AIHA patients with and without underlying SLE for the presence of aCL. aCL (IgG and IgM) were determined by ELISA in 74 SLE patients without AIHA, 22 SLE patients with AIHA, 50 patients with idiopathic AIHA (warm-reactive autoantibodies), 52 patients with idiopathic AIHA (cold-reactive autoantibodies) and 50 healthy controls. The mean IgG and IgM aCL titres in SLE patients without AIHA (IgG 37.0 U/ml, IgM 8.9 U/ml) were significantly elevated compared with the values in healthy controls (IgG 9.1 U/ml, IgM 3.2 U/ml; P < 0.005). The mean aCL levels in SLE patients with AIHA (IgG 53.2 U/ml, IgM 28.2 U/ml) were higher than in SLE patients without AIHA (P = 0.09 for IgG, P < 0.005 for IgM). Interestingly, the mean aCL levels of patients with idiopathic AIHA (warm-reactive autoantibody type: IgG 29.2 U/ml, IgM 19.3 U/ml; cold-reactive autoantibody type: IgG 27.4 U/ml, IgM 18.9 U/ml) were also significantly elevated compared with healthy controls P < 0.001). As aCL are elevated not only in SLE (with and without concomitant AIHA) but also in idiopathic AIHA it can be speculated that aCL are involved in the pathomechanism of autoantibody-induced erythrocyte destruction per se irrespective of an underlying SLE.

Anemia, Hemolytic, Autoimmune↗
PubMed1996

Non-tolerant B cells cause autoimmunity in anti-CD8 IgG2a-transgenic mice.

Using a pair of gamma 2a/chi immunoglobulin genes, transgenic mice were generated to study tolerance induction in B cells that express IgG2a autoantibodies. The transgenic IgG2a specifically binds CD8 alpha chains of the CD8.2 allotype expressed on the surface of CD8+ T cells, but not CD8 molecules expressed by the CD8.1 allele. Thus, IgG2a transgenic mice expressing the CD8.1 allele were used as controls to monitor B cell development and mice expressing CD8.2 were used to study B cell tolerance. Both types of mice showed transgenic gamma 2a expression on the surface of B cells. Expression of endogenous heavy chain alleles was strongly inhibited in immature B cell subsets, whereas mature B cells co-expressed transgenic gamma 2a and endogenous IgM/D. The transgenic chi chain expression leads only to partial allelic exclusion of endogenous light chains. B cells that express high levels of transgenic CD8.2-specific IgG2a were identified using soluble CD8-Ig. In CD8.1+ and in CD8.2+ mice, we found no differences in expression and maturation of transgenic anti-CD8.2 IgG2a+ B cells. High levels of serum anti-CD8.2 IgG2a antibodies led to the elimination of CD8+ T cells, causing a severe defect in cytotoxic immune responses. These results show that tolerance induction is incomplete in the CD8.2+ mice, either because IgG2a+ B cells are resistant to censoring mechanisms or because the secreted CD8-specific IgG2a antibodies render the CD8 autoantigen inaccessible to the B cells. This contrasts strongly with the efficient induction of B cell tolerance in mice expressing anti-CD8.2 IgM autoantibodies.

Animals↗