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P T Schellekens

Publications and source records attributed to P T Schellekens.

At least 19 recordsLinked to original sources
PubMed1996

Activation and increased expression of adhesion molecules on peripheral blood lymphocytes is a mechanism for the immediate lymphocytopenia after administration of OKT3.

We investigated the mechanism by which antihuman CD3 monoclonal antibodies of the isotypes IgG2a (eg, OKT3) and IgA (eg, IXA) can induce the rapid disappearance of virtually all circulating T lymphocytes. We hypothesize that upregulation of adhesion molecules on the lymphocyte membrane contributes to this effect. However, this hypothesis is difficult to test, because of the inherent lymphocytopenia and/or shifts in lymphocyte populations between intra and extra-vascular compartments. Therefore, studies in vitro were performed, as well. Analysis of peripheral blood lymphocytes isolated at several times after addition of OKT3 or IXA to whole blood of healthy individuals showed an immediate increase in the proportion of T cells expressing NKI-L16, an activation epitope on CD11a/CD18. Likewise, an increase in CD11b/CD18 expression occurred. In parallel experiments, a transiently increased adhesion of T cells to endothelial cell monolayers was observed. This adhesion could be completely blocked by anti-CD18 or anti-CD11a monoclonal antibodies and only partly by an anti-CD11b antibody. Our data indicate that upregulation of activation epitopes of CD11a/CD18, as well as increased expression of CD11b/CD18 on T lymphocytes, may result in increased adhesion of these cells to intercellular adhesion molecule-1 (ICAM-1) and ICAM-2 on vascular endothelium. This phenomenon may, at least, partly explain the rapidly occurring peripheral lymphocytopenia observed in vivo.

Adult↗
PubMed1995

Toxicity of OKT3 increases with dosage: a controlled study in renal transplant recipients.

In the present study we prospectively compared side effects occurring in 12 patients after the first administration of low-dose OKT3 (0.5 mg twice daily) induction therapy with those in 10 patients who were treated with a conventional dose of OKT3 (5 mg daily) for acute rejection. We also investigated cytokine release and activation of complement and neutrophils as all of these are held responsible for OKT3-induced side effects. Low-dose OKT3 resulted in a significantly decreased side effects score compared to that after a conventional dose of OKT3 (1.8 vs 5.1, p = 0.0006). Following the first administration of low-dose OKT3, TNF peak levels were significantly lower than after a conventional dose of OKT3. In contrast to our data on conventional dose OKT3 treatment, the first administration of low-dose OKT3 did not induce complement activation as reflected by C3a and C4b/c levels in plasma. Finally, the increase in neutrophil degranulation products lactoferrin and elastase-varies; is directly proportional to 1-antitrypsin was much less following 0.5 mg OKT3 than following 5 mg. We conclude that OKT3-induced toxicity is dose-dependent and is mediated not only by cytokine release but also by activation of complement and neutrophils.

Dose-Response Relationship, Drug↗
PubMed1995

T cell function in vitro is an independent progression marker for AIDS in human immunodeficiency virus-infected asymptomatic subjects.

The predictive value of low T cell reactivity to CD3 monoclonal antibodies for development of AIDS was evaluated and compared with low CD4+ cell numbers and the presence of syncytium-inducing human immunodeficiency virus (HIV) variants in 122 seropositive asymptomatic homosexual men for 4.5 years. Low T cell reactivity was a strong predictor for progression to AIDS in a multivariate proportional hazards analysis using these markers as covariates at entry and as time-dependent covariates. The combination of the three markers was associated with development of AIDS in 6 of 7 men within 15 months. In contrast, the group that lacked any of these markers had a very low risk (11%) for developing AIDS. In groups with one or two of these three markers, progression rates were 33% and 66%, respectively. These data demonstrate that measurement of T cell function in vitro is of value for staging of HIV infection and may be useful for monitoring therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Herpes zoster, immunological deterioration and disease progression in HIV-1 infection.

OBJECTIVE: To study the incidence of herpes zoster, the relationship between herpes zoster and immunological markers, and the prognostic value of herpes zoster for progression of HIV disease. DESIGN AND METHODS: A total of 966 homosexual participants in The Amsterdam Cohort Study were studied. Herpes zoster was defined by its characteristic clinical presentation. Incidence was calculated using Poisson regression, cumulative incidence by the Kaplan-Meier product-limit method and the prognostic value was evaluated using Cox proportional hazards model. RESULTS: The incidence of first episodes of herpes zoster was 3.31 per 1000 person-years (PY) in HIV-seronegatives and 51.51 per 1000 PY in HIV-1-seropositive individuals. Recurrences only occurred in HIV-1-positive patients (25.6%). Cumulative incidences of first episodes increased linearly with the duration of follow-up. In HIV-1-seropositives the incidence was 31.2 per 1000 PY at CD4+ cells > or = 500 x 10(6)/l, 47.2 per 1000 PY [relative risk (RR), 1.51; 95% confidence interval (CI), 0.78-2.94] at CD4+ cells 200-499 x 10(6)/l and 97.5 per 1000 PY (RR, 3.13; 95% CI, 1.54-6.32) at CD4+ cells < 200 x 10(6)/l. Besides CD4+ cell counts, CD3 monoclonal antibodies and phytohaemagglutinin-induced T-cell reactivity were independent predictors for herpes zoster. The hazard ratio for AIDS after herpes zoster was 1.6 (95% CI, 1.1-2.4) and for death 1.7 (95% CI, 1.1-2.5), but these were not independent from CD4+ cell counts. CONCLUSION: In HIV-1 infection the incidence of herpes zoster increases with the decrease of CD4+ cell counts and T-cell reactivity, but herpes zoster is not an independent predictor for disease progression.

Adult↗
PubMed1995

Effects of anti-CD3 monoclonal antibodies on functional activity of lymphocytes: studies in vivo and in vitro.

Lymphocyte functional activity was tested in 38 renal transplant recipients receiving induction treatment with various anti-CD3 MoAbs, i.e. OKT3, T3.G2a (an IgG2a anti-CD3 MoAb) or T3.A (an IgA anti-CD3 MoAb of the same idiotype). During treatment with OKT3 and T3.G2a, lymphocyte response to phytohaemagglutinin-P (PHA), as determined with the use of a whole-blood lymphocyte culture technique, decreased significantly. However, during treatment with T3.A PHA response was not affected. Using a conventional lymphocyte culture technique, PHA response was unchanged during treatment with all three MoAbs, indicating that the immunosuppressive effect of OKT3 and T3.G2a is probably dependent upon the presence of MoAb in culture medium and is reversible. In addition, we tested in vitro inhibition of aspecific mitogen- or antigen-induced lymphocyte stimulation by OKT3, T3.A and T3.G2a. It appeared that at low concentrations (< 25 ng/ml) T3.G2a and OKT3 exerted a stronger immunosuppressive effect than T3.A. However, at higher concentrations T3.A, OKT3 and T3.G2a were equally immunosuppressive. We conclude that the immunosuppressive effect of T3.A is caused by blindfolding. At low concentrations T3.G2a exerts its immunosuppressive effect mainly through modulation of the CD3 and/or T cell receptor complex, as a result of interaction with Fc receptors on monocytes. At higher concentrations blindfolding of the CD3/T cell receptor complex may contribute to immunosuppression.

Antibodies, Monoclonal↗
PubMed1995

Biphasic granulocytopenia after administration of the first dose of OKT3.

The effects of the administration of OKT3, a second immunoglobulin G2a (IgG2a) anti-CD3 monoclonal antibody (mAb), and its isotype switch variant IgA on granulocyte kinetics were compared for 5 hours after the first administration of the mAb. In addition, in vivo and in vitro studies were performed on alterations in expression of CD11b and CD62L induced by these mAbs. Within 15 minutes after administration OKT3 and IgG2a anti-CD3 mAbs induced a significant decrease in circulating granulocytes, whereas IgA anti-CD3 mAb did not. Apparently the initial decrease in circulating granulocytes depends on the heavy chain of the administered anti-CD3 mAb, resulting in immunocytoadherence and sequestration in the lungs. Increased adherence to pulmonary endothelium by altered expression of CD11b and CD62L plays a minor role in this first granulocytopenia, because each mAb exerted the same effects on these adhesion molecules in vitro. The second decrease in granulocyte counts occurred 60 minutes after administration of each mAb and correlated with a significant increase in expression of CD11b and CD62L in vivo and with upregulation of CD11b and down-regulation of CD62L in vitro. These alterations could be related to the presence of tumor necrosis factor-alpha both in vivo and in vitro. Thus granulocyte kinetics from 30 minutes after administration of each anti-CD3 mAb resemble neutrophil kinetics induced by TNF-alpha.

Adult↗
PubMed1995

Immunologic and virologic markers determining progression to AIDS.

Infection with the human immunodeficiency virus type 1 (HIV-1) results in a severe immunodeficiency characterized by a depletion of CD4+ T-helper cells. Furthermore, it is well documented that in asymptomatic persons the number of CD4+ cells is also a good predictor of progression to AIDS. However, persons with similar CD4+ cell counts may differ with regard to clinical progression. For this reason the development of additional markers predictive of disease progression is of major clinical importance. In this review three additional progression markers are discussed: rate of decline of CD4+ cells, T-cell reactivity, and HIV biological phenotype. Besides their usefulness as independent progression markers they also provided insight into immunopathologic mechanisms responsible for the eventual development of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Relationship between patterns of engraftment in peripheral blood and immune reconstitution after allogeneic bone marrow transplantation for (severe) combined immunodeficiency.

We report the outcome of allogeneic bone marrow transplantation (BMT) as treatment for severe combined immunodeficiency disease (SCID) in 31 patients grafted from 1968 until 1992. The patients received a graft from an HLA-identical related (n = 10), an HLA-haplo-identical related (n = 19), or a closely HLA-matched unrelated (n = 2) donor that resulted in the long-term survival of 6 of 10, 9 of 19, and 0 of 2 children, respectively. Major complications included failure of engraftment and early death caused by respiratory failure. The chimerism pattern and immunologic reconstitution were evaluated in 15 children who survived more than 1 year with sustained engraftment. The pattern of engraftment was investigated within flow-sorted peripheral blood (PB) T- and B-lymphoid, natural killer (NK), and myelomonocytic cell populations using the amplification of variable number of tandem repeats by the polymerase chain reaction. The immunologic reconstitution was assessed by various in vitro and in vivo parameters. Although the number of PB T cells and the in vitro T-cell proliferative response was in the lower region of normal in the majority of cases and even subnormal in some, in all cases donor T-cell engraftment and reconstitution of T-cell immunity was observed. Residual host-type T cells (1% to 5%) were detected in eight cases at multiple occasions. All children showed normal serum IgM and IgG subclass levels and produced specific IgG antibodies after vaccination, irrespective of donor B-cell engraftment. However, three HLA haplo-identical graft recipients with host-type B lymphoid and myeloid cells have a persistent selective IgA deficiency. NK cells were either of donor, host, or mixed origin. Donor NK cell engraftment restored defective in vitro NK cell function of the recipient. We conclude that determination of lineage-specific engraftment patterns provides valuable information for the understanding of the immunologic reconstitution after allogeneic BMT for SCID.

Antibody Formation↗
PubMed1994

Sequestration of labelled granulocytes in the lungs following administration of OKT3 is dose-dependent.

In the present study the consequences of administration of low-dose (0.5 mg) OKT3 for respiratory side-effects and pulmonary sequestration of labelled granulocytes are compared with the known effects of 5 mg OKT3. Ten renal transplant patients were studied, of whom five were treated with 0.5 mg OKT3 and five with 5 mg OKT3. None of the patients in the 0.5 mg group and two of the patients in the 5 mg group experienced dyspnoea. Sequestration of labelled granulocytes in the lungs was significantly lower in the patients receiving 0.5 mg OKT3 compared with the patients receiving 5 mg OKT3. The simultaneously occurring peripheral blood granulocytopenia was significantly more severe in the 5 mg group than in the 0.5 mg group. We suppose that this sequestration of circulating granulocytes in the lungs is at least partly mediated by complement activation products. In vitro it is demonstrated that fixation of complement activation products on peripheral blood lymphocytes depends on the concentration of OKT3 present in the culture medium. We conclude that respiratory side-effects shortly following infusion of OKT3 are related to complement-induced pulmonary leucostasis, the degree of which is dependent on the administered dose of OKT3.

Acute Disease↗
PubMed1994

Pretreatment with divided doses of steroids strongly decreases side effects of OKT3.

The aim of this study was to attenuate side effects of OKT3 by variation of the time interval between administration of corticosteroids and OKT3 in renal allograft recipients. In view of a maximal lymphocytopenia at six hours following MPNS, we postulated a greater preventive action on side effects from administration of methylprednisolone (MPNS) at six hours preceding the first dose of OKT3 compared to administration immediately before. Two groups of renal transplant patients treated for acute rejection with 5 mg OKT3 were studied. Ten patients received 500 mg MPNS six hours and ten patients one hour before administration of OKT3. We measured clinical side effects, body temperature, TNF and IL-6. There were no differences between the two groups regarding clinical side effects and peak body temperatures. However, MPNS administered six hours before administration of OKT3 diminished TNF release; MPNS one hour before decreased IL-6 release. We studied an additional group of six patients receiving 250 mg MPNS six hours before, followed by 250 mg one hour before OKT3. This group experienced significantly less side effects and lower body temperature. In addition, IL-6 levels were significantly decreased. We conclude that two times 250 mg MPNS administered six hours and one hour before the first administration of OKT3 effectively attenuates adverse reactions following administration of OKT3.

Adult↗
PubMed1994

Low-dose OKT3 induction therapy following renal transplantation: a controlled study.

In a prospective clinical study we tested the immunosuppressive properties and toxicity of low-dose OKT3 induction therapy in renal transplant recipients. 50 consecutive renal transplant recipients were alternatingly assigned to low-dose OKT3 induction or prednisolone/cyclosporin. Low-dose OKT3 induction treatment consisted of 0.5 mg OKT3 twice daily for 10 days, initially combined with azathioprine and prednisolone maintenance immunosuppression that was converted to prednisolone/cyclosporin at the end of the course. During a 15-29-month follow-up period, low-dose OKT3 induction therapy was found to reduce significantly the incidence of acute rejections, as compared to the usual prednisolone/cyclosporin maintenance immunosuppression (21 versus 52%, P = 0.02). There also was a tendency towards an improved graft function after low-dose OKT3, although no significance was reached. Furthermore, compared to a historical control group of renal transplant patients in whom acute rejection was treated with 5 mg OKT3 daily, low-dose OKT3 appeared to cause fewer side-effects. We conclude that low-dose OKT3 induction therapy is superior to prednisolone/cyclosporin in preventing acute rejection after renal transplantation and that it is better tolerated than conventional OKT3 treatment.

Adult↗
PubMed1994

Viro-immunological studies in acute HIV-1 infection.

OBJECTIVE: To monitor a patient who presented with symptomatic HIV-1 infection for virological and immunological parameters in relation to the clinical course. METHODS: Virological studies included determination of frequency of productively HIV-1-infected peripheral blood mononuclear cells (PBMC) and viral RNA load in plasma and p24 antigenaemia. Immunological studies included the analysis of T-cell subsets, the expression of activation markers, CD45RO and CD45RA antigens, the frequency of cells programmed for death, and T-cell function. RESULTS: During the first week post onset of primary HIV-1 infection symptoms high plasma titres of p24 and HIV-1 RNA were observed. The number of productively HIV-1-infected PBMC peaked, coinciding with CD4+ T lymphocytopaenia, during week 2 when clinical improvement started. CD8+ T lymphocytosis was observed 10 days post onset of clinical symptoms, the expanded cell population being of the CD8+CD38+, CD8+CD27+ and CD8+CD28- phenotype. CD8+ T lymphocytosis was paralleled by a high percentage of cells undergoing programmed cell death on in vitro culture. In vitro T-cell function was severely depressed during the first 10 days post onset of clinical symptoms. Within about 3 weeks, following resolution of clinical symptoms, phytohaemagglutinin-induced proliferation was restored to normal levels while responses to the CD3 monoclonal antibody only showed a partial restoration. During follow-up, concomitant with the rise of activated CD8+ T cells, p24 antigen levels and viral RNA load in serum as well as the number of HIV-producing PBMC steeply declined after 2 weeks. CONCLUSION: These findings demonstrate HIV-1-induced abnormalities during severe clinical symptoms of primary HIV-1 infection. The subsequent strong immune response, which is believed to be responsible for efficient control of viral replication, appears to precede clinical improvement.

Acquired Immunodeficiency Syndrome↗
PubMed1994

In vivo effects of IgA and IgG2a anti-CD3 isotype switch variants.

Side effects after the first administration of OKT3, a murine anti-CD3 monoclonal antibody (mAb) of the IgG2a class, are largely attributed to the release of cytokines as a result of T cell activation caused by interaction with Fc receptors (FcR) on human monocytes. As human monocytes possess FcR for murine IgG2a but not for IgA, it is expected that an anti-CD3 mAb of the IgA class causes less side-effects than an IgG2a anti-CD3 mAb of the same idiotype. To test this hypothesis we treated 20 renal transplant patients prophylactically with either IgG2a or IgA anti-CD3 mAb in a prospective randomized double-blind study. The patients received 0.5 mg anti-CD3 mAb, either IgA (T3.A) or IgG2a (T3.G2a), twice daily during 10 d. Rejection incidence after T3.A and T3.G2a was not significantly different. Side effects score after the first administration of mAb was significantly less after T3.A than after T3.G2a (0.7 vs 2.7, P = 0.002). IL-6 and gamma IFN levels increased significantly at 3 h after T3.G2a, but not after T3.A. The TNF peak level occurring at 1 h after T3.A was much lower than after T3.G2a. In plasma, complement and neutrophil activation products only increased after T3.G2a and not after T3.A. Both T3.A and T3.G2a resulted in a complete depletion of CD3+ cells, but after T3.A, CD3 depletion was of shorter duration than after IgG2a. Finally, in contrast to T3.G2a, T3.A did not affect coagulation and fibrinolysis. In conclusion, an anti-CD3 mAb of the IgA class causes hardly any cytokine release and less side-effects as compared with its IgG2a switch variant. Provided T3.A is sufficiently immunosuppressive, it is superior to OKT3.

Adolescent↗
PubMed1994

Immunological and virological markers determining progression to AIDS.

Infection with the human immunodeficiency virus (HIV-1) results in a severe immunodeficiency characterized by a depletion of CD4+ T-helper cells. Furthermore it is well documented that in asymptomatic persons the number of CD4+ cells is also a good predictor of progression to AIDS. However, persons with similar CD4+ cell counts may differ with regard to clinical progression. For this reason the development of additional markers predictive of disease progression is of major clinical importance. In this review three additional progression markers are discussed: rate of decline of CD4+ cells, T-cell reactivity and HIV biological phenotype. Besides their usefulness as independent progression markers they also provide insight into the immunopathological mechanisms responsible for the final development of AIDS.

Biomarkers↗
PubMed1994

Immunosuppressive drugs in clinical medicine.

Immunosuppressive drugs are agents capable of suppressing the development of at least one type of immune response in vivo at doses with minimal side-effects. Some characteristics regarding the mechanism of action of corticosteroids, azathioprine, cyclophosphamide, cyclosporine and monoclonal antibodies anti-CD3 are reviewed. Corticosteroids induce a redistribution of lymphocytes and display an anti-inflammatory effect; the immunosuppressive effect of azathioprine seems to consist mainly of its suppression of the inflammatory response; cyclophosphamide and cyclosporine influence the immune system itself and anti-CD3 monoclonal antibodies suppress cellular immunity fairly specifically. Finally, a brief summary of their use in renal disease, systemic vasculitis and connective tissue diseases is given.

Clinical Medicine↗