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E Roosnek

Publications and source records attributed to E Roosnek.

At least 55 records · Page 3Linked to original sources
PubMed1994

Relation between the resolution of HLA-typing and the chance of finding an unrelated bone marrow donor.

The chance of finding an unrelated bone marrow donor depends on the size of the donor registry, the frequency of the patient's HLA phenotype and the degree of histoincompatibility considered acceptable. We have studied 60 unrelated bone marrow donor searches and the probability of finding a donor when increasing HLA-compatibility requirements were applied. For 21 (35%) of the patients no donor could be identified who was (serologically) matched for all six ABDR antigens. For the remaining 39 (65%), a median of two (range 1-20) blood samples from serologically-matched potential donors was obtained for further analysis. Eighteen (30%) patients appeared to be mismatched with all the pre-selected donors because of DR (sub-)type mismatches detected by oligotyping. A further 7 (12%) patients did not have an MLC and/or cytotoxic T lymphocyte precursor (CTLp) negative donor. Thus, a 'perfectly matched' donor was found for 11 (18%) patients. To find a suitable donor for more patients we propose that many or all the potential donors identified in the various registries for a particular patient are simultaneously evaluated as many of the serologically ABDR-matched donors will appear to be incompatible after high resolution HLA-typing. This strategy will not only allow selection of the best matched donor more rapidly but the consequent use of high resolution typing might also lead to the definition of a certain number of acceptable mismatches.

Bone Marrow Transplantation↗
PubMed1993

Characterization of mixed chimerism in patients with chronic myeloid leukemia transplanted with T-cell-depleted bone marrow: involvement of different hematologic lineages before and after relapse.

We have characterized mixed chimerism (MC) in five patients with chronic myeloid leukemia (CML) who received transplants with T-cell-depleted bone marrow (BM) and who relapsed within 4 years after transplantation. To study the possible relation of MC with relapse, we purified different populations of leukocytes and analyzed their donor/recipient origin by a method based on polymerase chain reaction amplification of minisatellite DNA regions. Our results show that before relapse, all hematopoietic recipient cells are T cells, whereas monocytes, B, and natural killer (NK) cells are of donor origin. This observation does not appear to be specific for CML as similar results were found in two control patients with acute myeloid leukemia (AML). At the time of (CML) relapse, recipient granulocytes, monocytes, and erythrocytes appeared and progressively replaced the respective lineages of donor origin. No other lineages seemed to be involved as B cells and NK cells remained of donor origin and no significant changes in the number of recipient T cells were detected. In this respect relapse of CML after BM transplantation (BMT) seems not to be very different from the primary disease in chronic phase before transplantation. Furthermore, we conclude that after BMT, an association between mixed chimerism before relapse and the (CML) relapse does exist because both phenomena are consequences of T-cell depletion of the BM graft. However, this correlation might well be indirect as the MC caused by the recipient T cells appears to be independent of the one caused by the recurrent disease.

Adult↗
PubMed1993

The frequency of pretransplant donor cytotoxic T cell precursors with anti-host specificity predicts survival of patients transplanted with bone marrow from donors other than HLA-identical siblings.

Transplantation with bone marrow from other than genotypically HLA-identical donors is associated with an increased incidence and severity of graft-versus-host disease (GvHD). The precise influence of HLA incompatibilities is not easy to analyze as even perfectly matched, HLA-identical unrelated donors might still express HLA differences that remain undetected by conventional typing. To measure T cell activity against serologically detectable and nondetectable HLA antigens, we analyzed the frequencies of CTL precursors (CTLp) between 11 unrelated HLA-matched and five related haploidentical donor/recipient pairs in graft-versus-host direction. Our results show that whenever HLA class I disparities could be identified by serology, high precursor frequencies (1/28,000-1/94,000) were measured. In contrast, in donor/recipient pairs that differed for class II only, no precursors were detected. CTLp were elevated in two out of eight fully matched donor/recipient combinations. These combinations displayed activities as high (1/21,000; 1/52,000) as the combinations that were serologically HLA class I disparate. The incompatibilities detected by the cellular assay were highly significant for the clinical results after transplantation. High CTLp frequencies before transplantation correlated with unfavorable clinical results independent of the incidence of detected HLA differences. Five out of the six patients with high (> 1/100,000) CTLp frequencies died within 120 days after transplantation. GvHD IV was the cause of death for all (3/5) patients who had received an unmanipulated bone marrow. In the group with intermediate or undetectable CTLp frequencies, eight out of 10 patients are alive, seven (CTLp frequency undetectable) without GvHD more severe than grade II, while one patient (CTLp frequency = 1/180,000) suffered from GvHD grade III. One patient rejected the graft and was rescued by an autologous BMT.

Adolescent↗
PubMed1993

Replacement of HLA class II serology by the HLA-DR microtitre plate oligotyping assay: a one-year experience in unrelated bone marrow donor selection.

Because the selection of unrelated bone marrow donors requires a more accurate HLA-typing technique than is used for sibling donors, we have replaced class II serology by a rapid and highly discriminative HLA-DR DNA oligotyping assay on microtitre plates. We present here our 1-year experience with class II typing for 112 potential donors identified for 33 consecutive leukaemic patients. Although the donors were selected to be HLA-A, -B, -DR serologically identical, the microtitre plate oligotyping assay detected DR incompatibilities in 52.7% of the patient/donor pairs. One third was due to incorrect or incomplete typing of DR11 to DR16, the others to mismatches for the serologically indistinguishable subtypes of DR1, 11, 13 and 15, known to be relevant for T cell recognition.

Bone Marrow Transplantation↗
PubMed1993

Adoptive immunotherapy for recurrent CML after BMT.

Three patients with CML who relapsed after transplantation with T-depleted BM from their HLA-identical siblings were treated with transfusions of donor peripheral blood mononuclear cells, in combination with (short) IFN alpha 2 therapy. CML was successfully controlled as shown by the complete disappearance of Philadelphia-positive metaphases within 90 days of treatment. This treatment appears to be very effective as neither bcr-abl transcripts nor markers specific for hematological cells of recipient origin could be detected by very sensitive PCR techniques. Two patients treated in chronic phase are without evidence of disease 300 and 360 days after treatment. The third patient, treated in accelerated phase, died with BM aplasia, 39 days following PBMC infusions. Failure to detect residual donor-derived granulocytes, as was the case in this patient prior to initiating adoptive immunotherapy, may indicate loss of donor-derived BM activity. This may help predict and possibly prevent the occurrence of life-threatening aplasia after successful clearance of malignant hematopoiesis.

Acute Disease↗
PubMed1993

Characterization of pretransplant CTL activity in "perfectly matched" unrelated bone marrow donor/recipient combinations.

To characterize the pre-transplant cytotoxic T cell precursor (CTLp) activity of unrelated bone marrow donors towards their HLA-ABDR compatible recipients, we have established T cell clones from the primary (positive) CTLp cultures. Two "perfectly matched" oligo-typed DR/DQ identical combinations and two A/B identical, DR subtype incompatible combinations have been studied in detail. Analysis of the clones shows that in the first two combinations the alloreactivity was directed towards a subtype of A2 (A205) and a subtype of Bw60 respectively. In the other two cases, where class II incompatibilities were present, we have not yet defined the exact specificity. However, because the majority of recipient specific clones were of the CD8 phenotype, it is very likely that also in these two cases differences in class I are being recognized.

Bone Marrow Transplantation↗
PubMed1992

Evolution of mixed chimerism after allogeneic bone marrow transplantation as determined on granulocytes and mononuclear cells by the polymerase chain reaction.

To evaluate the clinical relevance of mixed chimerism (MC) after allogeneic bone marrow transplantation (BMT), we developed a method based on amplification of DNA minisatellites by the polymerase chain reaction (PCR). This sensitive method by which MC lower than 1% can be detected is applicable to any patient-donor pair. Furthermore, because the analysis requires only small amounts of DNA, it allowed us to analyze samples early after BMT and during graft rejection. Results were obtained within 48 hours after blood sampling. Determination of MC in granulocytes (GR) and in mononuclear cells (Mnc) was performed in 20 patients treated for various hematologic malignancies. In patients who received untreated BM, recipient cells disappeared rapidly after BMT. In patients transplanted with T-cell-depleted BM, MC occurred in 15 of 16 cases. The percentage of host Mnc was always significantly higher than the percentage of host GR. The evolution of MC in patients who received T-cell-depleted marrow showed distinct patterns depending on whether patients remained in continuous complete remission, relapsed, or rejected their grafts. During complete remission, a relatively stable and significant number of host cells could be detected during the first 2 years after transplantation. Thereafter, their number decreased, but even after 4 years, low numbers of host cells could persist. When the patients relapsed, an increase in host Mnc was monitored without significant changes in the number of donor Mnc. In contrast, after the relapse, donor GR were no longer detected. Two cases of graft rejection were studied. Directly after the onset of the rejection, donor GR and Mnc disappeared rapidly. During that period, no significant changes in the number of host Mnc were detected.

Adult↗
PubMed1991

Recognition by class II alloreactive T cells of processed determinants from human serum proteins.

Alloreactive T cells recognize a complex composed of an allogeneic major histocompatibility complex (MHC) molecule and a peptide derived from the processing of nonpolymorphic proteins. A sizable fraction of MHC class II alloreactive T cells is shown to recognize peptides derived from constitutive processing of human serum proteins. One such epitope is a fragment of human serum albumin. This epitope bound selectively to the human class II molecule DRw11 and was constitutively present on antigen-presenting cells in vivo. These data indicate that, in the case of MHC class II, peptides involved in allorecognition may originate from exogenous proteins.

Antigen-Presenting Cells↗
PubMed1991

Efficient and selective presentation of antigen-antibody complexes by rheumatoid factor B cells.

Using Epstein-Barr virus B cell clones and antigen-specific T cell clones, we asked how antigen-antibody complexes are handled by B cells. We found that the only B cells capable of efficient presentation of antigen-antibody complexes are those that bind the complexes via membrane immunoglobulin, i.e., rheumatoid factor-producing B cells and, to a lower extent, antigen-specific B cells. On the contrary, nonspecific B cells, although capable of binding antigen-antibody complexes, fail to present them to T cells. Thus, rheumatoid factor B cells can present any antigen in the context of an immune complex and be triggered by T cells specific for a variety of foreign antigens. These results demonstrate a mechanism of intermolecular help that may be responsible for the production of rheumatoid factor and possibly of other types of autoantibodies.

Antigen-Antibody Complex↗
PubMed1990

T cell activation by a bispecific anti-CD3/anti-major histocompatibility complex class I antibody.

A bispecific anti-CD3/anti-major histocompatibility complex (MHC) class I antibody (Ab) that is able to activate human T cells in the absence of a second signal has been used to compare activation by this Ab to signaling by anti-CD3 Ab or by antigen (Ag). We have studied early, intermediate and late events that occur after triggering of a tetanus toxoid-specific T cell clone. While bivalent anti-CD3 Ab induce transient (less than 20 min) intracellular Ca2+ concentration increases, the bispecific Ab, like antigen-presenting cells plus Ag, produces sustained (greater than 2 h) elevated intracellular Ca2+ concentration. In addition, while the anti-CD3 Ab only induces low levels of c-myc mRNA lasting less than 3 h, the bispecific Ab induces high levels which are maintained for at least 8 h after triggering. Late events, such as interleukin 2 receptor expression and proliferation, occurring more than 20 h after activation, were seen only when T cells were stimulated by bispecific Ab or by antigen-presenting cell and Ag. Cells activated by linking T cell receptor (TcR)/CD3 to MHC class I antigens could not be activated by cross-linking the MHC and TcR/CD3 structures separately. Therefore, we propose that the bispecific Ab functions by modifying the membrane dynamics of the TcR/CD3 complex, rather than by the generation of a second signal through class I antigens.

Antigen-Presenting Cells↗
PubMed1989

Triggering T cells by otherwise inert hybrid anti-CD3/antitumor antibodies requires encounter with the specific target cell.

We used a purified bispecific antibody (Ab) against CD3 and an ovarian carcinoma (OVCA) antigen to ask whether the binding of a monovalent ligand to CD3 can induce triggering of T cells. In the presence of OVCA cells, this Ab bridges the CD3 complex to the target cell and triggers proliferation and cytotoxicity in T cells. In the absence of target cells, however, this monovalent Ab, even when bound to T cells at high levels, fails to induce any increase in cytosolic Ca2+, nor does it induce responsiveness to IL-2 or modulation of the CD3 complex. Because it is inert when bound monovalently, this hybrid Ab can be used to arm in vitro CTL clones, which then retain the capacity to kill the specific tumor for up to 2 d.

Antibodies, Monoclonal↗
PubMed1988

T cells can present antigens such as HIV gp120 targeted to their own surface molecules.

To trigger class II-restricted T cells, antigen presenting cells have to capture antigens, process them and display their fragments in association with class II molecules. In most species, activated T cells express class II molecules; however, no evidence has been found that these cells can present soluble antigens. This failure may be due to the inefficient capture, processing or display of antigens in a stimulatory form by T-cells. The capture of a soluble antigen, which is achieved by nonspecific mechanisms in macrophages and dendritic cells, can be up to 10(3) times more efficient in the presence of surface receptors, such as surface immunoglobulin on B cells that specifically bind antigen with high affinity. We asked whether T cells would be able to present soluble antigens that bind to their own surface molecules. Here we show that such antigens can be effectively processed and presented by both CD4+- and CD8+-bearing human T cells. This indicates that T cells are fully capable of processing and displaying antigens and are mainly limited in antigen presentation by their inefficiency at antigen capture.

Antibodies, Monoclonal↗
PubMed1988

Kinetics of MHC-antigen complex formation on antigen-presenting cells.

With the use of flow cytometry, we recorded changes in intracellular ionized calcium [Ca2+]i of Indo-1 loaded T cells that were triggered by contact with APC. This rapid readout of TCR perturbation enabled us to monitor the formation of stimulatory Ag-MHC complexes on EBV-transformed B cells that were either pulsed with native tetanus toxoid (TT) or with a 12-amino-acid fragment of this protein. Neither unpulsed APC nor Ag-specific APC that were pulsed with native Ag and kept at +4 degrees C were able to induce changes in basal T cell [Ca2+]i in TT-specific T cell clones. After 1 h at 37 degrees C, however, the Ag-pulsed APC were able to induce a three-to-fourfold increase in [Ca2+]i. This length of time appeared to be almost independent of the concentration of Ag with which the APC were pulsed, suggesting that the lag time was due more to intracellular transit than to association of the processed Ag with the MHC molecule. Furthermore, the same lag time and independence of Ag concentration were found when the EBV-transformed B cells were pulsed with a mouse-anti-transferrin receptor mAb and tested for their capacity to trigger a T cell clone specific for processed mouse Ig. This indicates that, in addition to surface Ig, other receptors that are internalized can function in the same fashion in the uptake and processing of a soluble Ag. In contrast to what was found with intact native Ag, no lag time was observed when the APC were pulsed with high concentrations of a 12-amino-acid peptide, containing the amino acid sequence recognized by a TT-specific T cell clone, suggesting that the formation of MHC-peptide complexes occurs instantly. Pulsing with a lower peptide concentration, however, caused the appearance of a time-dependent increase in efficacy of Ag presentation, suggesting a slow accumulation of MHC-peptide complexes on the B cell membrane.

Animals↗