Biomedical subjects

P Lenert

Publications and source records attributed to P Lenert.

At least 19 recordsLinked to original sources

PubMed2005

Inhibitory oligodeoxynucleotides - therapeutic promise for systemic autoimmune diseases?

Recent studies have shed new light on a possible link between the innate activation of plasmocytoid dendritic cells and marginal zone B cells and the pathogenesis of systemic lupus erythematosus. Animal studies have identified that this response requires the Toll-like receptor 9 (TLR9). Engagement of the TLR9 by various ligands, including non-canonical CpG-motifs, can cause or aggravate pathogenic autoantibody production and cytokine secretion in lupus. Attempts to neutralize this activity either by blocking the acidification of the endosomal compartment with chloroquine and related compounds, or by preventing the interaction between the CpG-DNA sequences and TLR9 using inhibitory oligonucleotides could be a promising therapeutic option for lupus.

Animals↗

PubMed2001

Identification of methylated CpG motifs as inhibitors of the immune stimulatory CpG motifs.

The unmethylated CpG motifs within E. coli DNA (EC) cause immune stimulation. In contrast, mammalian DNA such as calf thymus (CT) DNA had been thought to be immunologically inert. In this article, we demonstrate that CT DNA unexpectedly specifically inhibits the immune activation by EC but not that by endotoxin. This inhibitory effect was mediated in the signaling pathway activated by EC since CT DNA markedly inhibited the CpG-induced nuclear translocation of the transcription factors, NF-kappaB and AP-1. In addition, CT DNA significantly inhibited the synergistic immune activation by EC and endotoxin. The mechanism of the inhibition by CT DNA probably did not involve the inhibition of the cellular uptake of EC. Using a CpG-depleted plasmid, we demonstrated that CpG methylation played an important role in the inhibition by CT DNA. Compared with unmethylated plasmid DNA, CpG-methylated DNA inhibited the immune activation by EC to the same extent as did CT DNA. Importantly, the inhibitory effect of CT DNA was also observed in vivo. Our results suggest that methylated DNA may be applied to alleviate the unwanted immune stimulation and inflammation in systemic inflammatory response syndrome and in gene therapy with plasmid DNA.

Animals↗

PubMed2001

CpG stimulation of primary mouse B cells is blocked by inhibitory oligodeoxyribonucleotides at a site proximal to NF-kappaB activation.

Bacterial DNA and CpG-oligodeoxyribonucleotides (ODN) are powerful B cell activators, inducing apoptosis protection, cell cycle entry, proliferation, costimulatory molecule expression, immunoglobulin (Ig) and interleukin-6 (IL-6) secretion. However, proximal events in B cell activation by ODN are only partially characterized, including the translocation of NF-kappaB to the nucleus. In this paper, we provide evidence that CpG-ODN-induced cell cycle entry and apoptosis protection are blocked by SN50 or gliotoxin and thus require NF-kappaB activation. NF-kappaB activation occurred within 30 minutes of stimulation of murine B cells with a phosphorothioate (S) CpG-ODN and persisted for up to 40 hours, with p50, p65, and c-Rel as the major components. Similar to other NF-kappaB inducers, CpG-ODN caused an early IkappaBalpha and IkappaBbeta degradation plus cleavage of the p50 precursor and subsequent NF-kappaB nuclear translocation. A group of closely related S-ODN, which specifically blocked CpG-induced B cell activation at submicromolar concentrations, also prevented NF-kappaB DNA binding and transcriptional activation. These inhibitory S-ODN differed from stimulatory S-ODN by having 2-3 G substitutions in the central motif. As inhibitory S-ODN did not directly interfere with the NF-kappaB DNA binding but prevented CpG-induced NF-kappaB nuclear translocation of p50, p65, and c-Rel and blocked p105, IkappaBalpha, and IkappaBbeta degradation, we concluded that their putative target must lie upstream of inhibitory kinase (IKK) activation.

Active Transport, Cell Nucleus↗

PubMed1997

Ig VH-dependent interaction between immunoglobulins and CD4.

CD4 interacts with the immunoglobulin (Ig)-VH domains by a virtue of its solvent-exposed C and C strands. These two strands also contribute to the full HIV-gp120 binding and participate significantly in binding to class II MHC molecules. In this paper we hypothesize that any high-affinity interaction between serum (or membrane-expressed) Ig and CD4 may have impact on early T cell activation events. The existing data provide evidence for different outcomes of a high affinity Ig/CD4 interaction on T cell proliferation and cytokine secretion: costimulation and inhibition. We will also discuss how a low affinity CD4/Ig interaction could play an important role in B cell stimulation initiated through surface Ig receptors, and how CD4 may be involved in shaping the B cell repertoire.

Animals↗

PubMed1996

Human CD4-reactive antibodies from SLE patients induce reversible inhibition of polyclonal T lymphocyte proliferation.

We report on isolation of human polyclonal CD4-reactive antibodies of IgM and/or IgG isotypes from several SLE patients. These antibodies bound specifically to CD4-expressing cell lines and to rCD4 in ELISA and immunoblots. Saturation of CD4-binding sites occurred at antibody concentrations between 5 and 15 micrograms/ml. Anti-CD4 antibodies, in a dose-dependent manner, suppressed the proliferative responses of human peripheral blood mononuclear cells (PBMC) to superantigens (Staphylococcal enterotoxins A and B), anti-CD3 antibodies, and mitogens (PWM and Con A, but not PHA). They could also inhibit the proliferation of highly purified human T cells induced by immobilized anti-CD3 antibodies. To promote their effects on T cells, human anti-CD4 antibodies had to be present at lymphocyte cultures before or at the time of priming. There was no significant inhibition when antibodies were added more than 24 h following T cell activation. Substantial evidence that the immunosuppression induced by anti-CD4 antibodies was due to their direct effect on T cells was obtained. Down-regulatory effect of anti-CD4 antibodies could be significantly reversed by addition of exogenous IL-2 and by preincubation with soluble recombinant (r)CD4. Interestingly, at least one affinity-purified anti-CD4 antibody could costimulate the T cell proliferation induced by superantigens or anti-CD3 antibodies, especially when used at subsaturating concentrations (1-4 micrograms/ml) and when added subsequently to the initiation of cultures.

Autoantibodies↗

PubMed1996

CD4-reactive antibodies in systemic lupus erythematosus.

An important place in the immune network is reserved for specific interactions between regulatory antibodies (Ab) and their ligands on T and B lymphocytes. Several lines of evidence indicate that the CD4 glycoprotein may be recognized by such Ab. High levels of CD4-reactive Ab occur in approximately 10-20% of HIV-infected patients. Moreover, between 20 and 30% SLE patients have Ab preferentially reactive with the CD4+ T cells. In relation to this, we have done studies aimed at demonstrating the existence and characteristics of Ab directly targeting CD4 in patients with SLE in comparison with rheumatoid arthritis and normal controls. Assessment of the CD4-reactive Ab by different approaches revealed a several-fold increase in serum concentration of anti-CD4 Ab restricted to a subset of SLE patients (n = 15/87, 17.2%). Enhanced binding was shown to occur specifically both on native CD4 (by immunofluorescence) and on recombinant CD4 (by ELISA and Western blot). Anti-CD4 Ab belonged to IgM and/or IgG isotypes. The overall binding of immunoglobulins to the CD4 molecule was not significantly contributed by DNA/anti-DNA and other circulating immune complexes, and there was no restriction in the usage of kappa and lambda light chains. Clinically, high CD4 reactivity occurred in SLE patients with active disease, as measured by the SLEDAI, and was associated with particular clinical manifestations, including neuropsychiatric disease and lymphopenia.

Adult↗

PubMed1996

[Systemic diseases: evaluation of important laboratory parameters in 3 cases with unusual skin changes].

A whole spectrum of various clinical and laboratory disorders in patients with skin changes, may present systemic disease manifestations. Serological parameters correlate with the progression of the disease. Authors present cases with unusual skin lesions and abnormal laboratory findings, that were presumed to be manifestations of the systemic disease progression. The first case is a report of a patient age 44, female with dermatomyositis that started suddenly from full health with generalized linear bluish dark erythematous lesion like excoriations, periocular heliotrope violaceous to dusky erythematous rash with edema in a symmetrical distribution involving periorbital skin with no pruritus, diagnosed on admission as the case of acute urticarica. In the second report, a 17-year old female was referred to us because of a spread up linear sclerodermia followed by high immunological disturbances. Our third case was a 21-year old female with a systemic lupus erythematous--Rowell syndrome, with skin lesions of erythema multiforme type with some similarities to dermatitis herpetiformis on the first examination.

Adolescent↗

PubMed1996

[Results of a multi-year study of persons with transplanted kidneys].

The authors review their results of five year follow up of renal transplantation. They summarised the results of treatment with three immunosuppressive regimens. There is an analysis of rejection episodes, recurrent glomerulonephritis, infections, surgical complications, a median graft as well as patient survival and other patterns of complications of renal transplantation.

Adolescent↗

PubMed1996

[Clinical and morphologic features in patients with acute nephritis syndrome].

Acute glomerulonephritis is a distinct clinical entity, more frequently found in younger age. We report 69 patients with AcGN (25 female and 44 male) mean age 26 years (range 15-58). The disease is clinically characterized with hypertension (57%), edema (59%) and oliguria (35%). Urine analysis showed microhaematuria/proteinuria (36%) and micro/macrohaematuria alone in 89%, while azothaemia was observed in 16% pts, and decreased serum complement levels in one third of patients, more often decrease of C3 (33%) than C4 (15%). Initial infection of the upper respiratory tract was seen in 65%, pneumonia in 8%. In 25% of pts. there were no data of previous infection. Cultures of pharyngeal smear revealed. Streptococcus only in 2 pts. Elevated AST titer was found in 32% pts. Eleven kidney biopsies were made, and histological examination showed 2 normal findings, 6 mesangioproliferative GH, 2 endocapillary GN and 1 membranoproliferative GN. Follow ups have showed urinary abnormalities in 25% of pts., without developing renal failure.

Acute Disease↗

PubMed1996

[Methylprednisolone pulse therapy in the early phases of lupus nephritis].

Renal involvement i.e. lupus nephritis (LN) in systemic lupus erythematosus (SLE) mainly determines course and outcome of the disease. Recognition of early manifestations of LN makes adequate therapy possible, with very good therapeutic results. We report 7 patients from a group of 150 SLE patients under our permanent control, 4 female and 3 male, mean age 21 years. All of them had signs of LN: proteinuria 7/7 haematuria 4/7 without azotaemia. Renal biopsy was performed in 6 pts, and histological finding was: class II 1 pt, class IV 3 pts and class V in 2 pts. In 4 pts tubulointerstitial changes were noted, while all showed immunofluorescent deposits of immunoglobulins and complement. Methylprednisolone "pulse" therapy (1000 mg, i.v., 3 days) followed by tapering of the steroid dose was given. Reduction of proteinuria and disappearance of haematuria were observed in all patients. During follow up, kidney function remained normal.

Adolescent↗

PubMed1995

Human recombinant CD4 and CD4-derived synthetic peptides agglutinate immunoglobulin-coated latex particles. Evidence that residues 25-28 and 35-38 of human CD4 form two separate immunoglobulin binding sites.

It has been shown previously that amino acid residues 21-49 of the first extracellular domain of human CD4 form the core of an immunoglobulin (Ig) binding site. Synthetic peptides of human CD4 that encompass this region also bind Ig and, with higher affinity, antigen/antibody complexes. Synthetic peptides also enhance binding of both monomeric and aggregated Ig to monocytic U937 cells and Staphylococcus aureus Protein A. To better characterize the nature of the Ig binding site on CD4, we tested the ability of human recombinant CD4 (rCD4) to agglutinate polystyrene particles coated with Ig. Evidence is presented that soluble rCD4 and CD4 peptide p21-49 were capable of specific agglutination of polystyrene particles coated with polyclonal Ig of either human or sheep origin. Agglutination could be blocked by soluble human polyclonal IgG or F(ab')2 fragments. Both heparin and sulfated dextrans also inhibit agglutination, suggesting that charged residues on rCD4 played an important role in agglutination mediated by rCD4 or CD4 peptide. Similarly, aurintricarboxylic acid (ATA) also blocked agglutination of Ig-coated particles by rCD4. Agglutination mapping studies performed using truncated peptides revealed the existence of two discrete, closely related Ig binding sites (residues 25-28 and 35-38).

Amino Acid Sequence↗

PubMed1995

[Chronic urticaria from the aspect of autoimmune diseases].

At some time in their lives one in a five persons is affected by urticaria and/or angioedema. The cause of urticaria may never be found in up to one quarter of patients with acute urticaria and in up to 90-95% with chronic urticaria. In this study we present results of our compounded approach (clinical follow up, laboratory findings, allergological testing) to patients with chronic urticaria and autoimmune diseases that progressed into chronic urticaria or started before the onset of the chronic urticaria. Our first case was a 56 year old woman with a 10 month history of chronic urticaria, angioedema and chronic gastritis before the diagnoses of insulin dependent Diabetes mellitus and Hypothyreoidismus primarius were established. Allergological testing reveals specific clinical significant immediate reaction to Balsam Peru. After adequate substitutional therapy was advocated and with specific clinical avoidance of offended allergen, remission was obtained. The second case was a 46 year old female suffering from chronic urticaria (with clinical features of urticaria like vasculitis) associated with hypocomplementemia (particularly C4 depressed) with negative antinuclear antibodies but positive circulating immune complexes after a 2 year follow up the patient developed Systemic lupus erythematosus. The third case was a 63 year old woman who developed chronic urticaria 3 years after total thyroidectomy, with pathological finding of Thyroiditis lymphocytaria-Hashimoto; after the allergological testing, positive lymphocyte transformation test revealed allergical sensitization to Vobenol was substituted with Thyvoral, complete remission was obtained.

Autoimmune Diseases↗

PubMed1994

Synthetic peptides of human CD4 enhance binding of immunoglobulins to monocyte/macrophage cells. II. Mechanisms of enhancement.

We have previously shown that a synthetic peptide corresponding to amino acid residues 21-49 of the first extracellular domain of human CD4 binds immunoglobulins (Ig) and antibody: antigen (Ab:Ag) complexes, and greatly enhances the uptake of aggregated Ig by monocyte/macrophage U937 cells. In this report, we investigated the mechanisms of enhanced uptake, and the contribution of different receptors present on the surface of monocyte/macrophage cells to this phenomenon. Our results indicate that both Fc receptor (FcR) and cell surface CD4 participate in the enhanced uptake of Ig promoted by the synthetic peptide of CD4. The involvement of these two receptors was demonstrated in experiments using monoclonal antibodies to FcR and CD4, as well as monosialoganglioside GM1, a substance known to modulate surface CD4. The participation of CD4 was further confirmed using the CD4 monocyte/macrophage cell line MM-6. Together, the results of these experiments indicate that surface CD4 may cooperate with FcR in handling aggregated Ig and Ab:Ag complexes. The implications of these findings for immunoregulation by Ab:Ag and idiotype:anti-idiotype (Id:anti-Id) complexes, and infection of macrophages by HIV, are discussed.

Antigen-Antibody Complex↗

PubMed1993

[Immunologic characterization of autoreactivity to nuclear antigens in patients with systemic lupus erythematosus].

Abnormal immune reactivity, with a production of multiple autoantibodies specially against the components of a nucleoplasm is one of the hallmarks of systemic lupus erythematosus (SLE). Our investigations were conducted on 102 patients with SLE, classified according to the criteria of ARA, aiming to better characterize the overall incidence of anti-nuclear antibodies in SLE, to determine the type of immunofluorescent staining of the nuclei, and to characterize the fine specificity of such antibodies using modified ELISA procedure. Results of our investigation show that 95% of patients with SLE have detectable anti-nuclear antibodies. Predominant pattern of nuclear staining is homogeneous, followed by a speckled type, while the rim (peripheral) pattern is relatively infrequent. Anti-nuclear antibodies showed the highest reactivity against native DNA (70% of patients), which was followed by binding to SS-A, eRNP and SS-B antigens. Interestingly, using ELISA procedure we could observe the reactivity against Sm antigen only in 5% of SLE patients. In patients who showed homogeneous or rim pattern of nuclear staining the predominant type of reactivity was against native DNA, while in patients with speckled type most frequent binding to non-histone proteins was observed. The most frequently observed individual pattern of ANA reactivity was of polyreactive type.

Adolescent↗

PubMed1992

Synthetic peptides of human CD4 enhance binding of Ig to monocyte/macrophage cells. I. Characterization and mapping studies.

Human T cell glycoprotein CD4 binds to class II MHC molecules and to HIV envelope protein gp120. We have shown that CD4 and synthetic peptides corresponding to amino acid residues 21-49 of the first extracellular domain of CD4, also bind Ig and, with greater avidity, antibody:Ag complex. We investigated the effect of CD4 synthetic peptides on the binding and uptake of human Ig by monocyte/macrophage U937 cells. We found that a synthetic peptide corresponding to amino acid residues 21-49 enhanced binding to U937 cells of both aggregated and nonaggregated Ig. The enhancement was concentration dependent, occurred both in normal and low ionic strength conditions, and varied with the time and the temperature of the preincubation step. The enhancement was maximal after preincubation for 3 h at 37 degrees C. A peptide concentration of 20 micrograms/ml was sufficient for optimal binding of both nonaggregated and aggregated Ig. CD4 peptide 21-49 also enhanced binding of Ig to Staphylococcus aureus protein A. These studies open a new perspective in the way monocyte/macrophage cells handle Ig, antibody:Ag or Id:anti-Id complex, in particular when present at threshold amounts in a nonprecipitating form.

Amino Acid Sequence↗

PubMed1992

[Prophylaxis and therapy of infections in allogenic bone marrow transplantation in patients with hematologic diseases].

Infection and acute graft versus host disease (GVHD) are the most common complications of allogeneic bone marrow transplantation, which compromise this therapeutical method for hematologic diseases. Beside the appreciation of customary preventive measures and the treatment of infections, it is necessary for every bone marrow transplantation center to analyze the development of bacterial, fungal and viral infections in the patients and to generate the most efficient and most rational program for their prevention and treatment. At the Hematology Department in Novi Sad seven allogenic bone marrow transplantations were performed in patients with malignant hematologic diseases and severe form of aplastic anemia. Prevention of the infection by isolation of the patient in a sterile unit, selective decontamination of the digestive tract with sterile food, skin and mucus hygiene and prophylactic drug administration proved rather beneficial and adequate for patients with the graft accepted, hematopoiesis recovered and immunity reconstructed. Risks of infections were increased by permanent vein catheter, acute GVHD and rejection of the bone marrow graft. Prompt isolation and identification of bacteria and fungi, especially in blood, the establishment of a minimal suppressing and bactericide antibiotic concentration, along with the assessment of their synergism, as well as early diagnosis of cytomegalovirus and administration of specific drugs, can significantly contribute to the more successful treatment of infections in transplanted patients.

Adolescent↗

PubMed1991

CD4/immunoglobulin interaction: implications for immune physiology and autoimmunity.

CD4 has an important role in T cell activation events that depend on its binding to non-polymorphic MHC class II determinants on antigen-presenting cells. Here, we provide evidence that CD4 also interacts with immunoglobulins (Ig). The Ig-binding region lies within residues 21-49 of V1 domain of CD4. Immunochemical studies suggest that this property of CD4 does not depend on the three-dimensional folding of the CD4 molecule. Synthetic peptides (p) encompassing amino acid residues 16-49 and 21-49 of CD4 bind immunoglobulins in comparable way to the intact molecule. In vitro p 16-49 enhances significantly idiotype/anti-idiotype and some weak antigen-antibody interactions. Antigen antibody complexes formed in antigen excess bind CD4 peptides with much higher avidity then non-complexed antibodies. The possible role of the CD4/Ig interaction in T-B cell cooperation is discussed.

Animals↗

PubMed1990

Human CD4 binds immunoglobulins.

T cell glycoprotein CD4 binds to class II major histocompatibility molecules and to the human immunodeficiency virus (HIV) envelope protein gp120. Recombinant CD4 (rCD4) bound to polyclonal immunoglobulin (Ig) and 39 of 50 (78%) human myeloma proteins. This binding depended on the Fab and not the Fc portion of Ig and was independent of the light chain. Soluble rCD4, HIV gp120, and sulfated dextrans inhibited the CD4-Ig interaction. With the use of a panel of synthetic peptides, the region critical for binding to Ig was localized to amino acids 21 to 38 of the first extracellular domain of CD4. CD4-bound antibody (Ab) complexed with antigen approximately 100 times better than Ab alone. This activity may contribute to the Ab-mediated enhancement of cellular HIV interaction that appears to depend on a trimolecular complex of HIV, antibodies to gp120, and CD4.

Amino Acid Sequence↗