Role of apoptosis in autoimmunity

Apoptosis is a physiological form of cell death required to ensure that the rate of cell division is balanced by the rate of cell death in multicellular organisms. Dysregulation of apoptosis is associated with the pathogenesis of a wide array of diseases: cancer, neurodegeneration, autoimmunity, heart disease and others. In this review we collect arguments supporting a hypothesis of a dysregulated apoptosis leading to development of autoimmunity like systemic lupus erythematosus (SLE). This notion is supported by occurence of known autoantigens in apoptotic blebs, in vitro findings of an increased rate of apoptotic lymphoblasts despite optimal cytokine stimulation combined with a defective in vitro clearance of apoptotic bodies by SLE phagocytes. Moreover, we and others could generate histone-specific lymphocytic cell lines from cells after activation with autologous apoptotic material. These lymphocytes could stimulate autologous B-lymphocytes to produce of anti-dsDNA antibodies, a diagnostic hallmark for SLE. Finally, antibodies against phospholipids like phosphatidylserine are often associated with systemic autoimmunopathies like SLE and others. Phosphatidylserine is exposed on apoptotic cells as early sign of programmed cell death and serves as phagocyte recognition molecule for apoptotic cells. Formation of immune complexes and deposition in tissues might lead to organ damage and disease. This scenario will be discussed in this review in detail.

TNF inhibitors in the treatment of arthritis

Rheumatoid arthritis (RA) is a chronic destructive arthritis leading to joint destruction as a consequence of chronic inflammatory processes. Established therapy with slow-acting disease-modifying anti-rheumatic drugs (DMARDs), as with low-dose methotrexate (MTX), leads to a significant improvement of disease symptoms, but are unable to stop joint destruction. Novel therapeutic agents like monoclonal antibodies (mAb), cytokine receptor-human immunoglobulin constructs or recombinant human proteins have been tested in RA and in other chronic arthritides like ankylosing spondylitis or psoriatic arthritis with convincing success. In particular, clinical trials testing anti-TNF alpha agents either alone or in combination with MTX have proven the feasibility and efficacy of these novel approaches.

Chlorpromazine induces apoptosis in activated human lymphoblasts: a mechanism supporting the induction of drug-induced lupus erythematosus?

OBJECTIVE

Drug-induced lupus erythematosus is a serious side effect of certain medications, such as procainamide, quinidine, hydralazine, chlorpromazine, and isoniazid, the underlying pathogenesis of which is unresolved. In this study, we examined the influence of these drugs on the regulation of apoptosis, or programmed cell death, in quiescent and activated human lymphocytes. We also discuss the dysregulation of apoptosis as a pathogenetic factor in systemic lupus erythematosus.

METHODS

Peripheral blood mononuclear cells or activated lymphoblasts from normal donors were incubated with different concentrations of each of the above-mentioned drugs.

RESULTS

We did not find induction of apoptosis in quiescent cells over a broad concentration range. In contrast, lymphoblasts readily underwent apoptosis when cultured with chlorpromazine, but not any of the other drugs, after stimulation with interleukin-2 (IL-2) in a dose-, time- and cell cycle-dependent manner. By several lines of evidence, toxicity was ruled out. Characteristic features of apoptosis-like incorporation of propidium iodide (PI), such as increased annexin V binding, changes in mitochondrial membrane potential, and induction of DNA breaks (as evidenced by TUNEL techniques), could be induced in lymphoblasts after chlorpromazine treatment. Chlorpromazine did not cause apoptosis by inhibition of cytokine binding or blockade of early intracellular signaling. The protease inhibitor Z-VAD and the ceramide inhibitor sphingosine 1-phosphate effectively blocked chlorpromazine-induced apoptosis (by PI staining and by externalization of phosphatidylserine), in contrast to the caspase 3/CPP32 inhibitor DEVD, which had only minor effects. Western blot analysis revealed IL-2-mediated phosphorylation of extracellular signal-regulated kinase, which was sensitive to chlorpromazine. Using lymphoblasts from a patient with Canale-Smith syndrome, we found that chlorpromazine-mediated apoptosis is Fas/ APO-1 independent.

CONCLUSION

These data suggest that chlorpromazine mediates apoptosis in human lymphoblasts through specific activation of intracellular proapoptotic signaling cascades. This mechanism might lead to an unsynchronized inflow of apoptotic break-down products and thereby to the induction of (auto)immunity against nuclear components.

Biological agents: a novel approach to the therapy of rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common chronic autoimmunopathy, clinically leading to joint destruction as a consequence of the chronic inflammatory processes. The pathogenesis of this disabling disease is not well understood, but molecular events leading to tissue inflammation with cartilage and bone destruction are now defined in more detail. Established therapy, slow acting disease-modifying antirheumatic drugs (DMARDs) as with low-dose methotrexate (MTX) are the accepted 'golden standard' therapies and both lead to a significant improvement of disease symptoms, however are unable to stop joint destruction. Due to these disappointing treatment options and the identification of some inflammatory mediators as therapeutic targets, novel therapeutic agents such as monoclonal antibodies (mAbs), cytokine receptor-human immunoglobulin constructs or recombinant human proteins have been tested in RA with some success. In particular, clinical trials testing anti-TNF-alpha agents either alone or in combination with MTX have convincingly demonstrated the feasibility and efficacy of these novel approaches to the therapy of RA. Importantly, a clinical trial testing combination therapy with chimeric (mouse-human) anti-TNF-alpha mAb cA2 (Remicadetrade mark) and MTX could, for the first time in any RA trial, show that average radiological progression in the cA2/MTX groups could be completely prevented over a 12 month observation period. Similar encouraging results might evoke from trials employing other TNF-alpha-directed agents like the fully human mAb D(2)E7 or the p75 TNF-alpha-receptor-Ig construct, etanercept.

CD 95-independent mechanisms of IL-2 deprivation-induced apoptosis in activated human lymphocytes

Growth factor deprivation-induced apoptosis plays an important role in several cellular systems. However, knowledge of the molecular mechanisms involved are restricted to a few murine models or tumor cell lines. Therefore, we aimed studying signaling pathways leading to apoptosis in activated human peripheral T cells after IL-2 withdrawal. Lymphoblasts from patients with CD 95 (Fas/APO-1)-deficiency revealed that functional CD95 was not required to induce apoptosis after IL-2 withdrawal. Moreover, apoptosis induction in response to various cytotoxic stimuli was found to be mediated in the absence of functional CD95 but was affirmatorily influenced by IL-2 signaling. Immunoblots showed no downregulation of Bcl-2 or Bcl-xL and no upregulation of Bax, whereas decreased mitochondrial membrane potential was readily measurable 24 h after cytokine deprivation. Tetrapeptide inhibitors showed limited efficacy in preventing apoptosis whereas the caspase inhibitor zVAD-FMK potently blocked induction of apoptosis. Cleavage of different fluorogenic substrates revealed multiple caspase enzyme activities in lymphoblasts, which were not negatively affected by the fas mutation. Starting at 8 h after IL-2 withdrawal, upregulation of active caspase-3 but not of caspase-8 could be detected. Taken together, our data argue for molecular mechanisms of cytokine deprivation-induced apoptosis in activated human lymphocytes independent of CD95.

[Hypereosinophilia with myocardial involvement due to toxocariasis. Diagnosis of regional myocardial perfusion abnormalities by pulsed tissue Doppler echocardiography]

CASE REPORT

The case of a 57-year-old woman is reported who was admitted for peripheral hypereosinophilia.

DIAGNOSIS

Detailed investigations revealed first of all a hypereosinophilic syndrome with infiltration of bone marrow and lung. The patient suffered more and more from angina pectoris with signs of heart failure. Coronary angiography was therefore carried out which showed normal coronary arteries. With suspicion of myocardial involvement endomyocardial biopsies were performed which revealed the presence of Löfflers endocarditis parietalis fibroplastica. Finally, serological studies for parasites disclosed a positive ELISA test for Toxocara, confirmed later to be rising.

CONCLUSION

Myocardial involvement of hypereosinophilia, caused by Toxocara is not described until now. Further diagnostic by means of pulsed wave tissue Doppler echocardiography provided regional differentiation of a restrictive filling pattern which documented the importance of this new diagnostic tool in myocardial illness.

In vivo blockade of tumor necrosis factor-alpha in patients with rheumatoid arthritis: longterm effects after repeated infusion of chimeric monoclonal antibody cA2

OBJECTIVE

To investigate the longterm consequences of tumor necrosis factor-alpha (TNF-alpha) blockade in patients with rheumatoid arthritis (RA), to compare changes after repeated infusion of cA2 monoclonal antibody with those occurring after the initial treatment, and to investigate significant correlations of cellular or serological changes to the duration of clinical benefit for each patient.

METHODS

A clinical trial testing TNF-alpha monoclonal antibody cA2 in treatment of RA showed this therapeutic agent is highly effective. A dosage of 1 mg/kg or 10 mg/kg cA2, given in a single infusion, was compared to placebo. After clinical relapse all patients were (re)treated with 3 or 10 mg/kg cA2. In parallel to this clinical study, we investigated cellular and molecular changes induced by in vivo blockade of TNF-alpha.

RESULTS

After an initial transient increase, T lymphocyte counts were not significantly different from starting values throughout the observation period. Monocyte counts as well as serum interleukin 6 (IL-6) and soluble intercellular adhesion molecule 1 (sICAM-1) concentrations remained decreased for several weeks after infusion. After a repeated infusion, increases in numbers of T cells and decreases in monocytes and IL-6 and sICAM-1 concentrations were evident again. Changes in cell counts, however, were smaller, especially in the group initially treated with the low dose (1 mg/kg), despite a higher retreatment dosage of 3 or 10 mg/kg cA2. Similarly, in this group decrease of IL-6 and sICAM-1 concentrations was less pronounced, was delayed to Day 7 after infusion, and lasted for a shorter period than seen after initial treatment.

CONCLUSION

We conclude that in vivo TNF-alpha blockade leads to prolonged cellular and serological changes. This effect appears to be less pronounced after repeated infusion of cA2 compared to the initial treatment, mainly in the low dose group.

Biologic agents in the treatment of inflammatory rheumatic diseases

In 1998, further details on the treatment of patients with rheumatoid arthritis with biologic agents became available. Biologic agents with established efficacy, e.g., the chimeric tumor necrosis factor-alpha monoclonal antibody cA2, were tested in combination with methotrexate (MTX), with evidence of synergistic effects. These trials revealed new, important information on the incorporation of tumor necrosis factor-alpha blocking agents into a treatment regimen of rheumatoid arthritis using established disease-modifying antirheumatic drugs and innovative biologic agents. Clinical trials testing new agents, e.g., T-cell receptor peptides in a double-blind, placebo-controlled fashion represented new developments with regard to T cell-directed treatment principles. In addition, new developments in the preclinical phase are discussed.

Preferential expression of tumor necrosis factor receptor 55 (TNF-R55) on human articular chondrocytes: selective transcriptional upregulation of TNF-R75 by proinflammatory cytokines interleukin 1beta, tumor necrosis factor-alpha, and basis fibroblast growth factor

OBJECTIVE

Articular cartilage is the main target for tumor necrosis factor-alpha (TNF-alpha) and interleukin 1(IL-1) actions. These cytokines are believed to mediate cartilage degradation in arthritis. We studied the expression of TNF receptors (TNF-R) on human articular chondrocytes and their regulation by IL-1beta, TNF-alpha, and basic fibroblast growth factor (bFGF).

METHODS

The expression of TNF-R55 and TNF-R75 on human nonarthritic articular chondrocytes was analyzed on protein and mRNA levels by ligand binding studies and reverse transcription polymerase chain reaction (RT-PCR) technique. The regulation of these receptors induced by IL-1 TNF-alpha, and bFGF on mRNA level was studied using RT-PCR.

RESULTS

Both TNF-R55 and TNF-R75 are expressed constitutively on human articular chondrocytes, and the number of both receptors varied between 822 and 3880 receptors per cell, depending on the donor cartilage used. Using TNF receptor-specific antibodies, we show that normal chondrocytes express mainly TNF-R55. These results are consistent with the mRNA data obtained by RT-PCR. mRNA expression of TNF receptors is regulated by IL-1beta, TNF-alpha, and bFGF. On human chondrocytes the expression of TNF-R75 mRNA was markedly upregulated by IL-ID, TNF-alpha, and bFGF, whereas the expression of TNF-R55 mRNA remained largely unchanged. A combination of IL-1beta and TNF-alpha, but not of IL-1beta and bFGF, showed an additive effect on TNF-R75 mRNA expression.

CONCLUSION

The expression of TNF-R55 and TNF-R75 on human articular chondrocytes is modulated independently by IL-1beta, TNF-alpha, and bFGF, suggesting a role of these regulatory mechanisms in the degradation processes of human articular cartilage in inflammatory joint diseases.

Increased spontaneous in vitro apoptosis in double negative T cells of humans with a fas/apo-1 mutation

We describe a 17 year old patient suffering from Canale-Smith syndrome (CSS) including chronic lymphadenopathy, splenomegaly, hypergammaglobulinemia and recurrent Coombs positive hemolytic crises. The parents are not consanguine, all other family members including two brothers are healthy. Peripheral blood mononuclear cells of the patient showed an increased rate of CD3 positive, CD4/CD8 double negative T-lymphocytes. In vitro assays showed these cells to have an increased rate of spontaneous apoptosis. Though expression of Fas/Apo-1 (CD95) and Fas-ligand (FasL) was detected on RNA- and protein level we found Fas/Apo-1 mediated apoptosis being significantly reduced. Sequencing of the fas/apo-1 gene proved the patient RT and his father to carry a point mutation at position 804 located in exon 9 (death domain) leading to an amino acid substitution. For developing of CSS, a fas/apo-1 mutation seems to be necessary but not sufficient. An additional independent mechanism must be involved in the pathogenesis of human lpr<-phenotype.

Epitope-specific signaling through CD45 on T lymphocytes leads to cAMP synthesis in monocytes after ICAM-1-dependent cellular interaction

We recently demonstrated that different CD45 monoclonal antibodies (mAb) are able to induce cellular aggregation in human peripheral blood mononuclear cells (PBMC) through LFA-1/ICAM-1 interactions. Such interactions could be down-modulated by protein kinase (PK) A/G inhibitors, but were unaffected by inhibitors of PKC, suggesting the involvement of PKA or PKG in CD45 mAb-induced adhesion. In this study we show that after incubation of PBMC with several (but not all) mAb to CD45, CD45RO and CD45RA, intracellular cAMP, but not cGMP concentrations readily increase, reaching a maximum 30 min after start of activation. As evidenced by several lines of investigation cAMP accumulation was independent of Fc receptor-associated signaling as well as tyrosine phosphatase activity of CD45. In highly pure T lymphocytes, CD45 mAb were unable to induce cAMP synthesis, but readily did so after addition of autologous monocytes. After paraformaldehyde fixation of both quiescent or IFN-gamma/TNF-alpha-preactivated monocytes, cAMP production was no longer detectable, suggesting monocytes as the cell of origin for the increased cAMP synthesis. Further, cAMP accumulation in monocytes occurred after reconstitution to T lymphocytes preincubated with CD45 mAb and extensively washed. Importantly, pretreatment of T lymphocyte/monocyte mixtures with LFA-1 mAb and/or ICAM-1 mAb down-regulated CD45 mAb-induced cAMP synthesis. Finally, we demonstrate that CD45 mAb are not only capable of inducing cAMP production, but also of directly stimulating PKA enzyme activity. Based on the data presented, we propose that CD45 signaling in T lymphocytes subsequently activates cAMP accumulation and PKA activation in monocytes via LFA-1/ICAM-1-dependent cellular interactions.

Histone-specific Th0 and Th1 clones derived from systemic lupus erythematosus patients induce double-stranded DNA antibody production

OBJECTIVE

To investigate whether histone-specific T helper (Th) cells that are able to induce anti-double-stranded DNA (anti-dsDNA) antibodies can be isolated from patients with systemic lupus erythematosus (SLE) and to characterize the cytokine secretion pattern of such Th clones.

METHODS

Peripheral blood mononuclear cells from SLE patients and healthy donors were stimulated with autologous apoptotic cell material or purified histones, expanded with interleukin-2 (IL-2), and cloned by limiting dilution. Histone reactivity of clones was examined by histone-specific proliferation and cytokine release. Cytokines were determined by enzyme-linked immunosorbent assay (ELISA) and CTLL-2 bioassay. Induction of anti-dsDNA antibodies was measured in cocultures of autologous B cells and Th clones by ELISA:

RESULTS

Numerous histone-specific T cell receptor (TCR) alpha/beta+ Th clones were established from 2 of 3 patients with active SLE and from 1 of 2 healthy individuals. Most Th clones secreted IL-2, interferon-gamma (IFNgamma), and IL-4, whereas some produced predominantly IL-2 and IFNgamma. Th clones that could stimulate the production of anti-dsDNA antibodies were derived from SLE patients and from a healthy individual.

CONCLUSION

Th cells specific for histones may play an important role in the pathogenesis of SLE by inducing autoantibodies to dsDNA. Both Th1 and Th2 cytokines may be involved in the pathogenesis of SLE. The presence of histone-specific Th cells in a healthy individual indicates the importance of peripheral tolerance for preventing autoimmunity to nuclear antigens.

[Pathogenesis of rheumatoid arthritis]

BACKGROUND

Despite ongoing intensive research using sophisticated new molecular tools and methods, the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA) is still not completely understood.

HYPOTHESES

In this paper the two favorite hypotheses of the pathogenesis of rheumatoid arthritis currently discussed are introduced and compared. Hypothesis 1 is focussing on the central role of the T cells and T cell dependent phenomena in the pathogenetic scenario of RA. In contrast, hypothesis 2 stresses the role of altered synovial fibroblasts and their specific features critical for the destruction of inflamed joints. Both hypotheses are thoroughly discussed and suggestions for further research activities are made.

CONCLUSION

Insights in the pathogenesis of RA provide options to develop new therapeutic strategies aimed at the inhibition of pathogenetic relevant processes.

Differential role for IL-2 and IL-15 in the inhibition of apoptosis in short-term activated human lymphocytes

Interleukin (IL)-15 is a newly described cytokine with properties similar to IL-2. Even though it does not share sequence homology with IL-2, both cytokines bind to the same receptor with the noted exception of a cytokine specific alpha-chain. In this study the authors compared IL-2 and IL-15 to determine their ability to rescue short term activated lymphocytes (phytohaemagglutinin stimulation of peripheral blood mononuclear cells for 6 days, followed by expansion in medium containing IL-2 for 2 days) from apoptotic cell death. The authors found that both IL-2 and IL-15 can inhibit induction of apoptosis in this experimental model with similar time and dose kinetics. On mRNA or protein levels induction of pro- and anti-apoptotic gene products like fasL, bcl-2, or bax with minor effects on fas/Apo-1 or bcl-XL was observed under culture conditions with both IL-2 and IL-15. Next, it was found that phytohaemagglutinin (PHA) blasts were less responsive (in terms of cellular proliferation and prevention from apoptosis) to IL-2 if signals through the alpha-chain were blocked, with no effect on beta-chain specific monoclonal antibodies (MoAb). By contrast, IL-15 was less effective in induction of cellular proliferation and prevention of apoptosis if IL-2R beta-chain specific MoAb were added to cell cultures. Testing intracellular signalling induced by IL-2 or IL-15, the authors found identical changes in tyrosine phosphorylation patterns in PHA blasts cultured in medium or under IL-2 or IL-15 stimulation. By contrast, they found consistent differences if PHA stimulated peripheral blood mononuclear cells (PBMC) were expanded in medium containing IL-15 (instead of IL-2). These IL-15 expanded PHA blasts showed a significantly increased percentage of apoptosis after growth factor withdrawal. Furthermore, IL-2 was more efficient than IL-15 in rescuing IL-15 expanded PHA blasts from apoptosis. In IL-15 expanded PHA blasts expression of IL-2R alpha-chain was lower than that in IL-2 expanded PHA blasts. A model presenting a differential role for IL-2 and IL-15 in inhibition of apoptosis in vivo is discussed.

In vitro apoptosis and expression of apoptosis-related molecules in lymphocytes from patients with systemic lupus erythematosus and other autoimmune diseases

OBJECTIVE

To analyze factors related to apoptosis in systemic lupus erythematosus (SLE) peripheral blood mononuclear cells (PBMC) and to compare the findings in SLE PBMC with those in normal donor PBMC or PBMC from patients with other autoimmune diseases.

METHODS

PBMC from normal healthy donors or patients with SLE, mixed connective tissue disease (MCTD), rheumatoid arthritis (RA), or various vasculitides were isolated. The percentage of apoptosis after activation through different signaling pathways was quantified using propidium iodide staining. Protein expression of Fas/APO-1 or bcl-2, and messenger RNA (mRNA) expression of bcl-2, bcl-xL, bax, bak, Fas/APO-1, Fas ligand (Fas-L), c-myc, mad, or max were determined.

RESULTS

We confirmed previous findings of increased numbers of apoptotic cells in SLE PBMC compared with normal donor cells after in vitro incubation. After activation of PBMC with CD28 monoclonal antibody plus phorbol myristate acetate (CD28 MAb/ PMA), staphylococcal enterotoxin B (SEB), or phytohemagglutinin (PHA), the percentage of apoptotic cells was unchanged (SEB) or diminished (CD28 MAb/PMA, PHA) in SLE cells, and the difference between normal donor and SLE cells was less pronounced. On the mRNA level, expression of apoptosis-related gene products did not differ between SLE cells and normal donor cells. Expression of Fas/APO-1 protein was increased in freshly isolated SLE T lymphocytes compared with normal donor T lymphocytes, whereas bcl-2 protein was up-regulated after a 3-day culture period. Cellular activation further increased bcl-2 protein levels, eliminating differences between normal donors and SLE patients. In RA cells, the percentage of apoptosis was similar to that in normal donor PBMC, whereas results using cells from patients with other autoimmune diseases (MCTD, Wegener's granulomatosis, Takayasu arteritis, polyarteritis nodosa) were comparable with those found using SLE PBMC. Addition of growth factors such as interleukin-2 (IL-2), IL-4, or IL-15 to culture medium decreased the percentage of in vitro apoptosis in both normal donor and SLE cells.

CONCLUSION

Based on these data, we conclude that accelerated in vitro apoptosis and increased Fas/ APO-1 and bcl-2 protein expression in SLE are nonspecific for the disease, and might be explained at least in part by the increased in vivo activation levels of PBMC from patients with SLE, MCTD, or autoimmune vasculitides combined with in vitro incubation under "noninflammatory" conditions and growth factor withdrawal.

Small DNA fragments isolated from human T-cell clones are enriched in sequences involved in DNA bending

IL-2 deprivation induces apoptosis in human IL-2-dependent T-cell clones. This process is characterized by typical cell morphology, changes in the cellular membranes and fragmentation of chromatin into units of single and multiple nucleosomes. We isolated apoptotic DNA of an IL-2-deprived T-cell clone and sequenced randomly selected fragments representing single and multiple nucleosomes.The frequency of phased adenosine tracts was markedly increased in the small apoptotic fragments as compared to oligonucleosomes. Our results thus indicate that chromatin fragmentation in human apoptotic T-cells is not random but preferentially involves DNA sequences with the capability to form bent DNA. Whether this indicates a colocalization of DNase cleavage sites and phased adenosine tracts on the chromosomes or a bias in selecting sites for apoptotic DNA fragmentation is discussed. Analysing the underlying mechanisms will shed new light on DNA degradation in apoptosis.

In vivo blockade of TNF-alpha by intravenous infusion of a chimeric monoclonal TNF-alpha antibody in patients with rheumatoid arthritis. Short term cellular and molecular effects

Due to the unknown etiology of RA, specific treatment is not available. Recently, in a double-blinded, placebo-controlled clinical trial, in vivo blockade of TNF-alpha by a single infusion of a chimeric TNF-alpha-blocking mAb, cA2, has proven to be highly effective in the treatment of RA. In parallel to this trial, we tested the consequences of cA2 infusion in ex vivo and in vitro experiments. In this paper, we describe an increase in CD4+ and CD8+ T lymphocyte counts on day 1 and a marked decrease in monocyte counts preferentially on day 7 after cA2 treatment, without major changes in B lymphocyte or NK cell counts. In addition, we found an increased responsiveness of PBMC to CD28 mAb/PMA, but not to CD3 mAb, superantigen staphylococcus enterotoxin B, or PHA on day 1 after infusion. The increase in DNA synthesis of PBMC was paralleled by increased IL-2 mRNA and IL-4 mRNA expression and IL-2 protein secretion in culture supernatants after in vitro stimulation of PBMC with CD28 mAb/PMA. In PBMC, we did not find any significant changes in mRNA or protein expression of CD28 Ag or CD28 ligands, B7-1 and B7-2. Serum concentrations of IL-1 beta, IL-6, and soluble CD14 were significantly diminished after in vivo TNF-alpha blockade. We did not see relevant changes in granulocyte function in vitro after cA2 infusion. Finally, we observed a statistically significant decrease in slCAM-1 molecules in the serum of patients treated with verum compared with that in the serum of subjects given placebo. This change in slCAM-1 concentration was evident on days 1 and 7 after the infusion of 10 mg/kg cA2, whereas it occurred only on day 7 in the serum of patients treated with the low dose (1 mg/kg) of cA2.

In vivo blockade of TNF-alpha by intravenous infusion of a chimeric monoclonal TNF-alpha antibody in patients with rheumatoid arthritis. Short term cellular and molecular effects

Due to the unknown etiology of RA, specific treatment is not available. Recently, in a double-blinded, placebo-controlled clinical trial, in vivo blockade of TNF-alpha by a single infusion of a chimeric TNF-alpha-blocking mAb, cA2, has proven to be highly effective in the treatment of RA. In parallel to this trial, we tested the consequences of cA2 infusion in ex vivo and in vitro experiments. In this paper, we describe an increase in CD4+ and CD8+ T lymphocyte counts on day 1 and a marked decrease in monocyte counts preferentially on day 7 after cA2 treatment, without major changes in B lymphocyte or NK cell counts. In addition, we found an increased responsiveness of PBMC to CD28 mAb/PMA, but not to CD3 mAb, superantigen staphylococcus enterotoxin B, or PHA on day 1 after infusion. The increase in DNA synthesis of PBMC was paralleled by increased IL-2 mRNA and IL-4 mRNA expression and IL-2 protein secretion in culture supernatants after in vitro stimulation of PBMC with CD28 mAb/PMA. In PBMC, we did not find any significant changes in mRNA or protein expression of CD28 Ag or CD28 ligands, B7-1 and B7-2. Serum concentrations of IL-1 beta, IL-6, and soluble CD14 were significantly diminished after in vivo TNF-alpha blockade. We did not see relevant changes in granulocyte function in vitro after cA2 infusion. Finally, we observed a statistically significant decrease in slCAM-1 molecules in the serum of patients treated with verum compared with that in the serum of subjects given placebo. This change in slCAM-1 concentration was evident on days 1 and 7 after the infusion of 10 mg/kg cA2, whereas it occurred only on day 7 in the serum of patients treated with the low dose (1 mg/kg) of cA2.

Donor specific bone marrow cells suppress lymphocyte reactivity to donor antigens and differentially modulate TH1 and TH2 cytokine gene expression in the responder cell population

Previous studies have shown that post-transplantation infusion of donor specific bone marrow following a non-specific potent immunosuppressive agent such as antilymphocyte globulin (ALG) can significantly enhance graft survival compared to ALG alone. This enhancement remains variable and is thought to occur through the induction of specific partial tolerance to the renal allograft, but the underlying cellular mechanisms have not been clearly identified. In order to improve the efficacy of this specific immunosuppressive treatment and to study the events leading to enhanced allograft survival, we sought to establish a simple in vitro model based on a mixed lymphocyte reaction (MLR). We show that cellular proliferation seen in a normal MLR can be suppressed by addition of donor specific bone marrow cells (BMC). Significantly, this suppression is not observed with either third party BMC or donor specific peripheral blood mononuclear cells (PBMC). We have defined the optimum conditions of bone marrow infusion regarding number of BMC, their handling and culture, and simple enrichment procedures. Using a semiquantitative polymerase chain reaction assay, we have studied the cytokine gene expression in MLR modulated by donor specific BMC. In an unmodified allogeneic response, the responder cells show increased expression of interleukin-2 (IL-2) gamma-interferon IFN-gamma and receptor (IL-2R) mRNA, and no IL-10 mRNA. When responder cells are cultured with BMC of the stimulator, there is a 256-fold decrease in IL-2 mRNA, and a 64-fold decrease in IFN-gamma and IL-2R mRNA. There is also a 64-fold increase in IL-10 mRNA. This effect is even more marked when the BMC are depleted of CD3+ cells. The kinetics of addition of donor specific BMC to the normal allogeneic MLR culture and specificity of the action of BMC are also elucidated. Our data suggest that the enhancement of graft survival observed with donor BMC may operate through decreased proliferation of reactive T cell clones (due to decreased IL-2/IL-2R) and suppressed monocyte functions (due to decreased IFN-gamma and increased IL-10 gene expression).

A rapid and simple method for the isolation of apoptotic DNA fragments

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The cell and molecular basis of leukocyte common antigen (CD45)-triggered, lymphocyte function-associated antigen-1-/intercellular adhesion molecule-1-dependent, leukocyte adhesion

We recently reported that cross-linking the leukocyte common antigen (CD45) can rapidly induce aggregation of human peripheral blood mononuclear cells via lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) interactions. Herein, we have examined both T-cell--monocyte cellular interactions and the molecular signaling that are involved in this phenomenon. Experiments using highly purified T lymphocytes showed that CD45-induced aggregation requires the presence of both T cells and monocytes. Cross-linking CD45 only on T lymphocytes, but not on monocytes, initiated cellular clustering after reconstituting to the respective untreated cell type. By several criteria, CD45-induced clustering of T cells to autologous monocytes was shown to be Fc-receptor--independent. When comparing intracellular signaling in leukocyte aggregation induced by CD45 cross-linking versus phorbol myristate-12-13-acetate (PMA) treatment, the former was found to be fivefold to 10-fold more sensitive to H-8, a reagent that effectively blocks cAMP- and cGMP-dependent protein kinases. On the other hand, reagents that increase intracellular cAMP levels (eg, dbcAMP, forskolin, and IBMX), protein kinase C (PKC) inhibitors (eg, staurosporine), and tyrosine kinase inhibitors (eg, herbimycin A and genistein) all readily inhibited PMA-induced, but not CD45 monoclonal antibody-induced, aggregation. We conclude that cross-linking the leukocyte common antigen on T cells induces LFA-1--/ICAM-1--dependent T-cell--monocyte aggregation through a unique signaling pathway independent of PKC, which involves instead cAMP-/cGMP-dependent protein kinases.