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A Ythier

Publications and source records attributed to A Ythier.

At least 19 recordsLinked to original sources
PubMed1992

Recombinant glycosylated human interleukin-6 accelerates peripheral blood platelet count recovery in radiation-induced bone marrow depression in baboons.

This report was aimed at confirming the potential clinical use for a genetically engineered glycosylated human interleukin-6 (rhIL-6) in hematopoiesis. Its tolerance and efficacy were assessed on hematopoietic restoration after neutron radiation-induced bone marrow injury on baboons, which represent an adequate model of parallelism for studying hematology in the human. The particular neutron radiation absorption pattern in the body allows the preservation of underexposed bone marrow areas that mimics an autotransplantation-like situation. An initial dose finding study (1 microgram up to 20 micrograms/kg/d for 8 consecutive days) in normal baboons established a dose-dependent response regarding the peripheral platelet count (range of increase, 1.5- to 4-fold). A significant elevation in white blood cell (WBC) count, as well as a substantial reversible normochromic normocytic anemia, were observed for the highest doses only (10 and 20 micrograms/kg/d). All rhIL-6 administered doses were clinically well tolerated. In myelosuppressed baboons, a selected dose of 10 micrograms/kg/d of rhIL-6 for 13 consecutive days significantly lessened the degree of induced thrombocytopenia as compared with the control group (P = .01) and shortened the time to occurrence of the nadir, showing that the onset of recovery occurs much earlier, ie, an average of 5 days (P = .003), in the treated group. Moreover, this accelerated platelet recovery is evidenced by an 8-day shorter mean time back to baseline values (P = .03) in the rhIL-6--treated animals. At this dose no effect was observed on the WBC recovery pattern. Importantly rhIL-6 did not accentuate the radiation-induced anemia and was clinically well tolerated. All tested monkeys recovered from their induced pancytopenia and no animal loss was recorded. IL-6, tumor necrosis factor, and IL-1 blood measurements are reported. In conclusion, rhIL-6 is a potent thrombopoietic factor for the treatment of induced thrombocytopenia in nonhuman primates at a clinically well-tolerated dose.

Animals↗
PubMed1986

Allogeneic responses of human fetal (22- to 25-week) peripheral blood lymphocytes: preferential recruitment of cytotoxic effector cells with both CTL activity and NK-like function.

In the present study, we have characterized human cytotoxic effector lymphocytes generated following in vitro immunization of normal fetal (22- to 25-week) peripheral blood mononuclear cells (FPBMC) by an allogeneic Epstein-Barr virus-transformed B-cell line termed LAZ388. Primary stimulations led to strong FPBMC proliferation. However, subsequent addition of LAZ388 cells to the cultures on Day 8 did not trigger conventional secondary responses. In fact, further proliferation of activated FPBMC required the addition of exogeneous interleukin 2. Cytotoxic activity generated in the mixed-lymphocyte reactions was assayed against LAZ388 immunizing cells as well as against the highly susceptible natural killer (NK) target cell line K562. Eight days after stimulation by LAZ388, there was no specific lysis and a moderate NK-like activity. However, following second and subsequent stimulations a strong killing was measured against both LAZ388 and K562 cells. Blocking experiments performed with relevant monoclonal antibodies suggested that cytotoxicity against immunizing cells was conventionally directed at MHC gene products. Effector cells were further studied using cloning procedures; it was found that all cloned cell lines able to kill LAZ388 cells were also strongly active against K562. Both types of cytotoxic function appeared to be mediated via surface receptors physically or at least functionally associated with T3 proteins.

B-Lymphocytes↗
PubMed1986

Natural killer clones derived from fetal (25 wk) blood. Probing the human T cell receptor with WT31 monoclonal antibody.

We have conducted a phenotypic and functional analysis of 19 cloned cell lines generated after allogeneic stimulation of circulating lymphocytes from a normal human fetus aged 25 wk. Using a limited series of mAbs (Anti-T3, WT31, T4, T8, and NKH1A), cloned cells were found to fall in three groups. Three clones have a conventional "inducer" phenotype. Three clones have a phenotype (T3+, WT31+, T8+, and NKH1A+) similar to that of certain NK active mature T lymphocytes present in adult peripheral blood. In contrast, 13 cell lines display surface characteristics that have not been described previously. Indeed, they express T3 proteins but not the WT31 determinant. In light of previous studies, these results show that WT31 mAb is a unique reagent directed at an invariant epitope of the human T cell receptor that is not present on all circulating T3+ fetal lymphocytes. Functionally the T3+, WT31+, and NKH1A+ clones were found to kill immunizing LAZ 388 cells, as well as K562, while T3+, WT31- and NKH1A+ clones display NK-like function exclusively. Moreover, only WT31+ lymphocytes present in the cell line used for cloning experiments have the capacity to recognize alloantigen-bearing cells. Together, these data suggest that expression of WT31 may be necessary for recognition of alloantigens, while NK reactions mediated by T3+ lymphocytes are WT31-independent.

Animals↗
PubMed1986

Generation of monoclonal antibodies blocking cytotoxic reactions by human NK clones: further characterization of a 40/80-kDa target cell receptor.

To study NK target antigen(s), mice were immunized with pooled cells from five human hematopoietic cell lines (K562, MOLT4, JM, CEM, U937) known to be susceptible to Natural Killer activity. Cells fusions were performed and 4 out of approximately 2000 hybridoma supernatants were selected because of their ability to block cytotoxic reactions between a human NK clone (termed JT9) and MOLT4 cells. Functional characterization of the four monoclonal antibodies (Mabs) indicated that individual treatment of each immunizing target cells resulted in a decreased cytotoxicity. This inhibition was very specific because it was exclusively observed when three clones, JT9, JT10, and JT11, which express the same clonotypic structure (NKTa), were used as effector cells. Parallel and sequential immunoprecipitations showed that the four reagents termed anti-TNKtar 1, 2, 3, and 4 were directed at the same 40/80-kDa heterodimeric structure previously identified by anti-TNKtar Mab. However, cross-blocking experiments indicated that TNKtar and TNKtar 1-4 represent two distinct epitopic clusters. Finally, it was shown that anti-TNKtar 1-4 recognition sites are either identical or closely related to that of an additional antibody termed 4F2. Together, the present data strengthen the hypothesis that the activation antigen recognized by these series of Mab serves as a target cell receptor for at least a minor population of NK active lymphocytes.

Animals↗
PubMed1986

Characterization of antileukemia cells' cytotoxic effector function. Implications for monitoring natural killer responses following allogeneic bone marrow transplantation.

We have studied here cytotoxic function of three cloned cell lines--TC12, 48, and 50--derived from circulating lymphocytes that were potentially able to eliminate residual tumor cells in a patient transplanted for treatment of acute lymphocytic leukemia. These cloned cells, which have both phenotypic and functional characteristics of natural killer lymphocytes, were tested in chromium release assays against a panel of 16 uncultured populations of leukemia cells. In addition, their activity was compared with that of cloned and uncloned NK cells from normal individuals. It was found that TC clones induced a much weaker degree of killing against fresh tumor cells compared with conventional NK target cell lines such as K562 or MOLT 4. In addition, there was great heterogeneity in their individual lytic capacity against the various leukemia blasts (TC12, 48, and 50 cells killed in a significant fashion, respectively 7, 1, and 4 of the 16 leukemias), reflecting the functional diversity of normal NK cell populations. Thus, for a fraction of leukemias, there was no correlation between lytic ability of TC cells and that of uncloned lymphokine-activated large granular lymphocytes from normal peripheral blood. Together, these results support the view that direct identification of patients' cytotoxic lymphocytes screened against in vivo relevant tumor cells is necessary to evaluate potentially beneficial immunologic responses in the context of bone marrow transplantation.

Bone Marrow Transplantation↗
PubMed1986

Characterization of natural killer cells with antileukemia activity following allogeneic bone marrow transplantation.

To identify cells with potential antileukemia activity following bone marrow transplantation, we have monitored immunologic reconstitution in a patient with acute lymphocytic leukemia in second remission who received intensive chemotherapy and total body irradiation followed by infusion of allogeneic histocompatible marrow. Prior to transplantation, donor bone marrow cells were depleted of T lymphocytes by in vitro treatment with anti-T12 monoclonal antibody and rabbit complement. In the first 3 weeks following bone marrow transplantation, the predominant regenerating mononuclear cell population in peripheral blood exhibited a phenotype characteristic of natural killer (NK) cells. After 4 weeks, T lymphocytes became predominant, but NK cells persisted. Cultured peripheral blood lymphocytes obtained 12 weeks posttransplant were able to display significant cytotoxicity against leukemic blasts that had been cryopreserved at the time of relapse 5 months prior to bone marrow transplantation. To further characterize those cells with antileukemia activity, we used in vitro cloning techniques to identify four monoclonal populations, termed TC12, -48, -50, and -59, with strong antitumor activity. Cytogenetic analysis demonstrated that each clone was of donor origin. Phenotypic characterization showed that the four clones expressed NKH1A but did not express T3, T4, or T8 antigens. Three of the four clones expressed T11/E rosette antigen. Each clone exhibited strong cytotoxicity against genetically unrelated hematopoietic tumor cell lines such as K562, Molt-4, JM, and U937. In addition, we found that these patient clones were similar to cloned NK cells previously derived from normal individuals. Taken together, these results suggest that at least some clones with antileukemia activity following bone marrow transplantation are cells with NK-like function and phenotype. Functional analysis of these cytolytic cells in larger numbers of patients will be necessary to determine the clinical significance of this finding.

Adult↗
PubMed1986

Short-term culture of acute myeloid leukemia blasts: analysis of acquired susceptibility to activated natural killer cells.

Following a cryopreservation step, short-term cultures of circulating leukemic blasts from a patient with acute myeloid leukemia (AML) were performed. Because cultured tumor cells became susceptible to natural killer (NK) activity, in vitro alteration of the blasts was studied. Immediately after thawing, cell suspensions consisted of a relatively homogeneous population of undifferentiated blasts. In culture, tritiated thymidine uptake by the leukemic cells was low during the first 24 hours and then increased (X20) to a peak on day 7. The cell concentration started to increase on day 4. On day 8, less than 10% of the cultured cells still appeared as undifferentiated blasts, whereas up to 60% were granular and 30% to 40% had a monocytoid morphology. Prior to being cultured, the blasts were resistant to resting and IL2-activated natural killing. When the kinetics of in vitro acquired susceptibility were studied, it was found that maximum cytotoxicity against these leukemic cells was reached within 24 hours. Thus, the blasts had become NK-sensitive prior to increase in DNA synthesis, proliferation, and differentiation based on morphological and cytochemical criteria. In contrast, there was a positive correlation between acquired susceptibility and surface expression of an activation antigen, termed TNKtar. To dissect further the mechanisms of acquired susceptibility, a series of six NK clones representing four distinct phenotypes of NK active lymphocytes were tested against the leukemic cells. Immediately after thawing, blasts were essentially resistant to all clones, whereas they were strongly killed by 5 of 6 clones when cultured for 24 hours. Cold target inhibition assays indicated that resistance of fresh blasts was likely to be due to a binding defect. These results suggested that tumor cells became susceptible because they surface-expressed NK target structure(s) in the early phase of an activation process leading to their proliferation and/or differentiation. This hypothesis was substantiated for one clone, termed JT9, because the anti-TNKtar antibody blocked cytotoxicity of JT9 cells against the cultured blasts.

Adult↗
PubMed1985

Administration of an anti-interleukin 2 receptor monoclonal antibody prolongs cardiac allograft survival in mice.

Administration of the monoclonal antibody M7/20, which binds to the murine interleukin-2 (IL) receptor, significantly prolongs cardiac allograft survival in two H-2-incompatible strain combinations of inbred mice. The results support the important role of the IL-2 receptor in the mechanism of graft rejection, and suggest its suitability as a target for immunosuppressive therapy.

Animals↗
PubMed1985

Proliferative responses of circulating human NK cells: delineation of a unique pathway involving both direct and helper signals.

The present studies were performed to investigate mechanisms of human natural killer (NK) cell activation. NK-active cells were purified out of heterogeneous large granular lymphocytes (LGL)-enriched suspensions using a "pan NK"-specific monoclonal antibody termed anti-NKH1A. It was found that treatment of NKH1A+-sorted cells by T lymphocyte mitogens such as phytohemagglutinin (PHA) or anti-T11(2) plus anti-T11(3) did not induce proliferative responses. In fact, there was no measurable interleukin 2 (IL2) secretion and no significant increase in IL2 susceptibility following incubation with either PHA or anti-T11(2) plus anti-T11(3). However, as opposed to small resting T lymphocytes, NKH1A+ cells moderately proliferated in the presence of IL2. This IL2-dependent proliferation was dramatically increased after interaction between NK-active lymphocytes and certain hematopoietic cell lines such as K562 or EBV-transformed lymphoblastoid cell lines. These studies indicate that unique activation mechanisms can be identified when NK lymphocytes are purified out of LGL-enriched fractions. The NK activation pathway delineated here appears essentially distinct from those described for T lymphocytes. Indeed the nature of the NK cell/inducing cell interaction is unknown and triggering cannot be related, for example, to a conventional allogeneic effect mediated through membrane exposure of class I or class II major histocompatibility complex gene products. Moreover, these interactions do not lead to the development of autocrine responses. Together the present results support the view that direct signals can preactivate NK cells but are not sufficient to trigger proliferation which must therefore be regulated by helper populations.

Antibodies, Monoclonal↗
PubMed1985

The effect of anti-interleukin-2 receptor monoclonal antibody on allograft rejection.

During immune response to an allograft, activated T cells express a number of cell surface activation antigens, among them the membrane receptor for the lymphokine interleukin 2 (IL-2). As the IL-2 receptor is not present on resting T cells, it offers an attractive target for potentially specific immunosuppressive therapy. The rat monoclonal antibody M7/20, which binds to the murine IL-2 receptor, was studied for its effect on allograft survival in two H-2-incompatible strain combinations in inbred mice. Treatment with M7/20 for 10 days markedly prolonged survival of vascularized, heterotopic heart allografts in both strain combinations, with indefinite graft survival in 50% of recipients. The same treatment significantly prolonged skin allograft survival in one of the two combinations. The results support the important role of the IL-2 receptor in the mechanism of graft rejection and confirm its suitability as a target for immunosuppressive therapy in transplantation.

Animals↗
PubMed1985

[Interleukins: factors of intercellular communication].

Immune response implies reactions between immunocompetent cells. These reactions are made by direct contact between cells and via soluble factors. Among the latter, the interleukins, protein molecules produced during antigenic and mitogenic stimulation by the immunocompetent cells, intervene as modulators of the immune response. Interleukin-1, a protein synthesized by the activated macrophages, participates in the induction of interleukin-2 production by stimulated T-lymphocytes. Interleukin-2, a glycoprotein molecule, is the growth factor of activated T-lymphocytes by enabling their proliferation and clonal propagation. Interleukin-3, or Multi-colony stimulating factor, controls the production and the differentiation of haemopoietic cells and thus probably plays an important role in resistance to infections.

Animals↗
PubMed1985

A target structure for a series of human cloned natural killer cell lines is recognized by both anti-TNKtar and 4F2 monoclonal antibodies.

It was shown recently that a surface antigen termed TNKtar was likely to serve as a target molecule for three distinct human NK clones expressing the same clonotypic determinant (termed NKTa) present on a 90 KD recognition structure. In the present studies, we investigated whether TNKtar and a previously described antigen termed 4F2 were related. Parallel immunoprecipitations from membrane lysates of the same cells showed that both anti-TNKtar and 4F2 Mab precipitate a heterodimeric structure which resolves as two bands of identical m.w. (40 and 80 KD) in SDS-PAGE analysis under reducing conditions. Sequential immunoprecipitations demonstrated that the two antibodies are directed at the same molecule. However, one antibody did not block subsequent binding of the other, and vice versa, suggesting that anti-TNKtar and 4F2 Mab are directed at two distinct epitopes of the molecule. Functionally, it was found that 4F2 Mab was able, as well as anti-TNKtar, to selectively block cytotoxic function of JT9 cloned cells. Furthermore, as reported previously for anti-TNKtar, 4F2 had no effect when additional NKTa-NK clones were used as effector cells in cytotoxicity assays. Finally, cold target inhibition assays were performed by using cold target cells precoated with either anti-TNKtar or 4F2 Mab. These experiments showed that preincubation of target cells with either antibody blocked their ability to compete with their radiolabeled counterpart. Such results further strengthen the hypothesis that the activation antigen recognized by both anti-TNKtar and 4F2 Mab serves as a specific target structure for NKTa+ NK active clones. We discuss the importance of previous data concerning the 4F2 molecule in light of this functional role, which had not been identified previously.

Antibodies, Monoclonal↗
PubMed1983

Improved culture conditions for quantitative evaluation of interleukin 2 production by frozen human lymphocytes.

Several culture parameters were studied in order to establish methods for optimal and reproducible production of interleukin 2 (IL2) by thawed lymphocytes. Standard conditions, considered optimal for production by freshly separated lymphocytes (culture medium RPMI 1640 + 1% normal human serum + 10 micrograms/ml PHA), gave low and poorly reproducible results. An increased concentration of human serum (10 and 20%) in the medium improved production but best results were obtained by adding polyethylene glycol (PEG 6000, 0.1 mg/ml) to the culture medium. Furthermore, with the addition of PEG 6000, results became highly reproducible, thus permitting valid comparison of in vitro IL2 production by lymphocytes from normal donors and patients.

Blood↗
PubMed1983

HLA-AB and -DR types in patients with infectious mononucleosis (IM).

The frequency of HLA-A, -B and -DR antigens in 48 infectious mononucleosis (IM) patients was studied and the antigen frequencies were compared with those of a local panel. The resulting data do not confirm the association of IM and HLA-B35 as reported in a previous work. A high and significant frequency of blank HLA-DR phenotypes was noticed in IM population during the acute phase, but HLA-DR phenotypic expression was restored after recovery. This lack of expression could be the result of modified HLA-DR expression on circulating EBV infected B lymphocytes.

Adolescent↗
PubMed1983

Plasma exchange in early kidney graft rejection associated with anti-donor antibodies.

Patients with early rejection of kidney allografts associated with anti-donor antibodies have been randomized in two groups which received, respectively, either the conventional corticosteroid/azathioprine treatment or extensive plasma exchanges (PE) plus the conventional treatment. Data on the monitoring of anti-T or anti-B donor lymphocytes, as well as anti-panel or autoreactive cytotoxicity are described. Although the titer of anti-donor antibodies is decreased in the PE-treated group there is no sustained improvement of graft function compared to the control group. Thus, in these stereotyped rejection episodes, which are likely to be antibody mediated, there is no significant effect of extensive and early plasma exchange.

Antibodies↗
PubMedDate not supplied

Decrease in natural killer cell activity in kidney allograft recipients.

The natural killer cell activity (NKCA) of a population of 66 functioning kidney allograft recipients (followed up for over 9 years) was assessed on K562 and DORA cell line targets. The 51Cr specific release test showed a rapid, sharp decrease in NKCA as early as 3 months after grafting, reaching a minimal level between 7 and 60 months (5 +/- 5 vs. 45 +/- 19% 51Cr release; P less than 0.001). Patients showing an almost total lack of NKCA were roughly the same whether assessed on K562 or DORA targets. NKCA tended to be restored in long-term transplanted patients (greater than 61 months). Control populations, aside from 32 healthy individuals, consisted of 11 haemodialysed patients as well as patients submitted to corticosteroid therapy for more than one year (8 cases of giant cell arteritis and 4 chronic asthmas). Haemodialysed patients exhibited normal NKCA (whether previously grafted or not). Corticosteroid-treated patients showed either no significant modification (K562 target) or a borderline decrease (DORA target) in NKCA. Azathioprine or corticosteroid dosage intake on the day of the test did not influence the level of graft recipient NKCA. The natural cytotoxicity of peripheral blood lymphocytes (PBL) from recipients lacking in activity (less than 5% 51Cr release) was not restored by exogenous (type alpha) interferon. and PBL of recipients with low NKCA scores produced normal levels of purified interferon after 24-h Sendai virus exposure. No inhibitory effects of sera obtained from recipients lacking NKCA nor any active suppressor cells from their PBL could be evidenced, thus suggesting an actual loss of natural killer progenitors (or an "insensitivity" to interferon) in those patients. Corticosteroids, as opposed to azathioprine, were able to decrease the in vitro NKCA of healthy donor PBL at pharmacological concentrations.

Adult↗
PubMedDate not supplied

A unique T-cell receptor complex expressed on human fetal lymphocytes displaying natural-killer-like activity.

We have recently derived a series of cloned cell lines displaying natural killer (NK) cell-like activity from normal human fetal blood (25 weeks). The lines were obtained after repeated stimulation of mononuclear cells with allogeneic Epstein-Barr virus (EBV)-transformed B lymphocytes and are interleukin-2 (IL-2) dependent. Initial characterization of the clones has been reported previously. Certain of these clones have been found to have unusual surface characteristics, namely, they are recognized by several well-defined anti-T3 antibodies, but do not react with WT31, which is thought to recognise an invariant epitope of the human (Ti-alpha beta) structure. Transcription of the genes encoding the alpha- and beta-chains of the T-cell receptor was assessed in two of these clones (F6A4 and F6C7). Ti-beta genes were found to be expressed, whereas alpha messenger RNA was not detected in Northern blot analysis. These data strongly suggest that these cells do not produce a stoichiometric T3/Ti-alpha beta receptor complex. However, experiments performed with a monoclonal antibody (anti-NKFi) developed against F6C7 cells demonstrated the existence of a unique clonotypic structure [relative molecular mass (Mr) 85,000 (85K)] which is surface-associated with T3 proteins. Furthermore, both anti-T3 and anti-NKFi were found to block cytotoxic effector function. Together, the results support the view that T3 proteins are involved in non-major histocompatibility complex (MHC)-restricted cytotoxic reactions mediated by certain circulating fetal lymphocytes which are likely to use a clonotypic structure distinct from both the 'first' (alpha beta) and the putative 'second' (gamma delta) T-cell receptor to recognize their target. The present studies were designed to characterize this structure.

Antibodies, Monoclonal↗