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Biomedical subjects

C Mawas

Publications and source records attributed to C Mawas.

At least 55 records · Page 3Linked to original sources
PubMed1989

Anti LFA1 monoclonal antibody for the prevention of graft rejection after T cell-depleted HLA-matched bone marrow transplantation for leukemia in adults.

A mouse IgG monoclonal antibody (MoAb) directed against the human LFA1 molecule (25.3 MoAb) was used in nine adult leukemic patients to prevent graft rejection after T cell-depleted HLA matched bone marrow transplantation. Based on the results of a previous study in children 0.1 mg/kg of 25.3 was given on days -3, -1, +1, +3, +5 in addition to a standard conditioning regimen with cyclophosphamide (120 mg/kg) and fractionated total body irradiation. The marrow transplant was T cell-depleted using T101 Fab immunotoxin ricin A chain. Seven patients received post-graft immunosuppression with methotrexate and cyclosporine A; two patients received no immunosuppression post-graft. A mean T cell depletion of 98.3% (80-100%) was achieved. Tolerance to the infusions of 25.3 MoAb was excellent. No patient developed any form of graft-versus-host disease. However two patients failed to engraft and three patients had delayed graft failures. These results show that this regimen of anti LFA1 MoAb, which was extremely good at permitting engraftment of HLA mismatched T cell-depleted transplant in children with constitutional diseases, is not able to prevent graft failure and rejection of T cell-depleted HLA matched transplants in adults with leukemia. Further efforts are needed to overcome graft failures in this clinical situation.

Adult↗
PubMed1988

Triggering CD 28 molecules synergize with CD 2 (T 11.1 and T 11.2)-mediated T cell activation.

Pairs of monoclonal antibodies (mAb) defining epitopes T 11.1 and T 11.2 on the CD 2 molecule are mitogenic for purified human T cells in the presence of a submitogenic dose of 12-O-tetradecanoylphorbol 13-acetate (TPA). Anti-CD 28 mAb can substitute for the action of TPA in the anti-CD 2-induced proliferative response of resting T cells, whereas each signal alone is unable to mediate this effect. Co-stimulation by anti-CD 2 plus anti-CD 28 mAb is monocyte independent and besides resting T cells also induces strong proliferation of thymocytes and pre-activated T cells. Modulation of the CD 3-T cell receptor complex does not inhibit the co-stimulatory effects of anti-CD 2 plus anti-CD 28 mAb. The effect is largely dependent on endogenously produced interleukin 2, since the response is strongly inhibited in the presence of mAb against the 55-kDa interleukin 2 receptor chain.

Antibodies, Monoclonal↗
PubMed1988

Selective depletion of marrow-T cytotoxic lymphocytes (CD8) in the prevention of graft-versus-host disease after allogeneic bone-marrow transplantation.

In vitro depletion of mature pan-T lymphocytes has been widely and successfully used to prevent acute graft-versus-host disease (GVHD) after allogeneic bone-marrow transplantation (BMT). However, this procedure has been associated with a high incidence of graft failure and leukemic relapse. In this pilot study, we evaluated the efficiency of a selective depletion of human marrow T cytotoxic lymphocytes (CD8), a subset essential to induce GVHD in mice. Eleven patients with hematologic malignancies were included (7 HLA-matched BMT, 4 HLA-mismatched BMT). Marrow treatment with 7 anti-CD8 mAbs and rabbit complement resulted in a marked reduction of CD8+ lymphocytes from 15% (median value; range 7%-31%) to 1% (median value; range less than 1%-11%). Acute GVHD was not abolished by this procedure despite postgraft immunosuppression. One patient (HLA-mismatched BMT) rejected his graft and had a full autologous recovery. In conclusion, when compared to the data in the literature, CD8 depletion was shown to be less efficient than pan-T-cell depletion in the prevention of GVHD after allogeneic BMT and was still associated with a major complication associated with this procedure, i.e., graft failure.

Adolescent↗
PubMed1988

Elimination of leukemia cells from human bone marrow using floating beads.

A new in vitro immunophysical method of removing leukemia or lymphoma cells from autologous bone marrow is described. This new technique makes use of low-density polypropylene beads (density: 0.91) coated with a monoclonal antibody anti-CALLA (antibody ALB2). To ascertain its ability to selectively remove human B/pre-B hematopoietic cells, this technique was applied to normal human bone marrow cell suspensions contaminated with 1-5% of tumor cells. Samples were incubated with the floating beads at 4 degrees C on a rotating wheel for 60 min, followed by a 10-min decantation period, after which the beads bearing the tumor cells floated on the surface, whereas unbound normal marrow cells remained in suspension and were easily recovered free of beads. To demonstrate the feasibility of our method, 2 types of assays were carried out, one using target cell radiolabeled with 111indium, and the other a clonogenic assay. The first assays were to calibrate the different parameters (cellular density, quantity of beads, incubation time) with tumor cell lines: Namalwa (CALLA+) and Molt 4 (CALLA-). These 2 cells lines being able to clone, it is hard to envisage clonogenic assays. In this case, it is very hazardous to evaluate correctly the remaining clonogenic units of Namalwa cells. It is why radiolabelling assays were used for these first experiments. The second assays were to study a model close to the clinical setting and to control the safety of the beads on normal bone marrow cells. In this case, the mixture experiments in which only Namalwa cells were able to clone were evaluated with clonogenic assays, which are more sensitive than radiolabeling assays. A 3- to 4-log reduction of tumor load was achieved with 1-step treatment, and an average of 5-log depletion was obtained by repeating the process twice, as ascertained by the clonogenic assay. Viability, average recovery of nucleated cells, and stem cells potential following the purge were excellent.

Antibodies, Monoclonal↗
PubMed1987

Prevention of rejection of kidney transplants by monoclonal antibody directed against interleukin 2.

The effect of 33B3.1, a rat IgG2a monoclonal antibody (MAb) directed against interleukin 2 receptors on activated T lymphocytes, was studied during the first two weeks after transplantation in an attempt to prevent rejection in primary, cadaveric, kidney transplant recipients. 9 patients received 5 mg 33B3.1 daily by intravenous infusion for 14 days (group A) and 18 received 10 mg daily (group B). Both groups also received prednisone and azathioprine. In threatened rejection, rescue treatment consisted of anti-thymocyte globulin (ATG). 33B3.1 was well tolerated, with mild fever during the first 2 days being the most common side-effect. 3 patients in group A had a reversible acute rejection episode before day 14, whereas only 1 patient in group B had reversible rejection. 20 of 30 historical control patients (prednisone/azathioprine) and 2 of 55 patients previously treated with ATG had a rejection episode in a similar period after transplantation. Trough levels of 33B3.1 in the blood ranged from undetectable to 1.6 micrograms/ml in group A and from 0.3 to 9 micrograms/ml in group B. Most patients had antibodies against 33B3.1 by the end of treatment.

Acute Disease↗
PubMed1987

Parameters of interaction of a novel monoclonal antibody (33B3.1) with the human IL2-receptors: interrelationship between 33B3.1, anti-Tac, and IL2 binding sites.

This report describes the molecular parameters of interaction of a new antibody (33B3.1) with the human membrane RIL2 expressed by ConA-activated T lymphocytes or allogeneic T-cell clones established from a rejected kidney allograft: the 33B3.1 immunoprecipitates a membrane protein of 55000 MW. It inhibits IL2-driven proliferation of activated T cells. This inhibition occurred in the nanomolar range when low concentrations of recombinant IL2 (rec-IL2) were used. The (125I)-33B3.1 binds in a specific way to a single class of receptor sites on activated T cells. The rate constants of association and dissociation at 37 degrees C of the labeled 33B3.1 were k*1 = 12 X 10(5) M-1 s-1 and k*-1 = 7 X 10(-4) s-1, respectively, and its equilibrium dissociation constant was KD = 0.65 nM. Maximal binding capacities were fairly variable among T-cell clones, as high as 300,000 sites/cell for some of them. Competition experiments demonstrate that the 33B3.1 and anti-Tac interact with the RIL2 in a competitive manner, suggesting that they recognize closely associated epitopes on the RIL2. However, the 33B3.1 inhibits the binding of (35S)-recombinant IL2 to its high affinity RIL2 in a noncompetitive way. The 33B3.1 seems therefore to interact with an epitope close but distinct from the IL2 binding site. Our data could suggest either that the 33B3.1 is able to convert high affinity RIL2 towards low affinity conformations or that there is more than one IL2 binding site per molecule of high affinity RIL2.

Antibodies, Monoclonal↗
PubMed1987

Generation of CD8 cytolytic T cells early after autologous or allogeneic bone marrow transplantation.

Longitudinal in vitro assays related to cell-mediated immunity were performed in patients following allogeneic (32) or autologous (15) bone marrow transplantation (BMT). In both groups of reconstituted patients, low CD4+/CD8+ T cell ratio and weak allogeneic mixed lymphocyte reactions were found in the first 6 months after BMT, progressively reaching values similar to controls (bone marrow donors or unrelated individuals). In contrast, a strong generation of allogeneic cytotoxic cells, assessed by the number of lytic units per 10(6) cells, was frequently found (18/38 patients tested in both groups) in the first 4 months, despite the quantitative deficit of the CD4+ subset. This in vitro differentiation was found to be independent of in vivo acute graft-versus-host disease (GVHD) and chronic GVHD in allo-transplanted patients. As also documented in autologous recipients, this observation suggests that this phenomenon could be, at least partially, related to the transplantation per se. Preliminary characterization of the effector cells indicates that they belong to the CD8+ subset and that their differentiation is interleukin-2-dependent. Experimental depletion of the CD4+ subset in normal subjects did not increase the number of lytic units in allogeneic cultures. This implies qualitative differences between BMT recipients and normal subjects, namely in CD8+ subset: i.e. that following BMT early CD8+ T cells appear to produce their own growth factor (IL-2), while in normal adult individuals, such autocrine CD8+ T cells, if present, are very rare.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1986

Prevention of graft failure by an anti-HLFA-1 monoclonal antibody in HLA-mismatched bone-marrow transplantation.

Seven patients with immunodeficiencies (Wiskott-Aldrich syndrome, combined immunodeficiency, and osteopetrosis) were given a mouse monoclonal antibody against the alpha subunit of human leucocyte functional antigen (HLFA-1; CD18) to facilitate the engraftment of mismatched haploidentical related-donor bone marrow. Other conditioning included busulphan, cyclophosphamide, and antilymphocyte globulin. To prevent graft-versus-host disease the bone-marrow T cells were depleted with sheep erythrocyte rosetting and cyclosporin therapy was given. HLFA-1 antibody injections were well tolerated without side-effects except slight, transient fever (38-40 degrees) after the first injection. Engraftment was rapid in all seven patients. The regenerating leucocytes were of donor origin in all cases, and two patients have a mixed chimera. Two patients died from infections. The others are alive and well 60-395 days after transplantation. In a historical control group given the same treatment without anti-HLFA-1 infusion, only one of seven transplants partially engrafted; only two patients remain alive with autologous reconstitution but with uncorrected immunodeficiency.

Antibodies, Monoclonal↗
PubMed1986

Defective membrane expression of the LFA-1 complex may be secondary to the absence of the beta chain in a child with recurrent bacterial infection.

Membrane and intracellular processing of the LFA-1 macromolecular complex, known to be involved in cytolytic function of T lymphocytes, was investigated in a child with recurrent bacterial infections, impaired natural killer activity, T cell-mediated lymphocytolysis and absent adhesion and migration of phagocytic cells. Monoclonal antibodies to the LFA-1 alpha and beta subunits, able to precipitate the LFA-1 alpha, 180-kDa chain, the p151 chain and beta 94-kDa chain (shared by both alpha chains), were used in immunoprecipitation studies of patient and control phytohemagglutinin-blasts. Neither of the alpha chains nor the beta chain were found in precipitates obtained from 125I-surface-labeled patient cells in contrast to controls. However, the precursor of the LFA-1 alpha chain, a 170-kDa polypeptide, was identified in lysates of biosynthetically labeled patients' cells. These results suggest that the defective membrane expression of the LFA-1 complex may be secondary to the absence of the mature beta chain.

Antigens, Surface↗
PubMed1986

Anti-interleukin 2 receptor monoclonal antibodies. Respective role of epitope mapping and monoclonal antibody-receptor interactions in their antagonist effects on interleukin 2-dependent T cell growth.

Functional studies, using mainly interleukin 2 (IL2)-dependent growth of human T cell lines or clones but also mixed lymphocyte cultures and mitogen T cell activation, allowed a collection of locally produced anti-IL2 receptor monoclonal antibodies (mAb) to be classified. They fell into two groups: one with strong to moderate inhibition of IL2, the other without any detectable functional activity in in vitro assays. Direct and sequential immunoprecipitation as well as peptide mapping confirm that all the mAb recognize the same surface molecule. The parameters responsible for such functional dichotomy were characterized: the main parameter was found to be linked to the epitopic cluster recognized on the molecule by the mAb. All functional mAb pertained to a given epitopic cluster and all the nonfunctional ones to an alternative cluster. Studies on mAb receptor and IL2 receptor interactions confirmed these findings and strongly suggest that functional mAb interact with a region on the IL2 receptor identical or very close to the site of ligand-receptor interaction. These data could facilitate the choice of mAb to be used in therapeutical approaches in vivo when ethical objections could be overcome by appropriate committees.

Antibodies, Monoclonal↗
PubMed1986

Anti-CD2 (sheep red blood cell receptor) monoclonal antibodies and T cell activation. I. Pairs of anti-T11.1 and T11.2 (CD2 subgroups) are strongly mitogenic for T cells in presence of 12-O-tetradecanoylphorbol 13-acetate.

A large collection of monoclonal antibodies (mAb) directed against sheep red blood cell (SRBC) receptor (cluster of differentiation 2: CD2) were classified according to three criteria: their inhibitory effect on T cell-SRBC rosette formation; the epitopic cluster recognized on the CD2 molecule; their reactivity with resting or activated T cells. All mAb were then tested in a two by two checkerboard fashion for possible T cell mitogenicity, in presence or absence of a submitogenic dose of 12-O-tetra-decanoylphorbol 13-acetate (TPA), an agent known to be comitogenic for T cells, presumably in delivering a second signal, usually accessory cell dependent. The combined data demonstrate that in the absence of TPA only few pairs of mAb directed at distinct epitopes of the CD2 molecule were mitogenic for T cells (in approximately 30% of the population tested), and in the presence of a submitogenic dose of TPA the majority of T11.1 anti-CD2-mAb (9 out of 11) were strongly mitogenic for T cells of all individuals tested when paired with T11.2 anti-CD2 mAb. The two anti-T11.1 mAb, noncomplementary to anti-T11.2 mAb, were, however, strongly mitogenic when added to mAb of the T11.3 subgroup, represented by 1-Mono-2A6. Taken together, these data strongly suggest that the main characteristic of T cell mitogenesis triggered by anti-CD2 mAb is the requirement for a signal delivered simultaneously to two different epitopes of the CD2 molecule, whether these epitopes are T11.1, T11.2 or T11.3.

Antibodies, Monoclonal↗
PubMed1986

Modulation of surface T11 molecules induced by monoclonal antibodies: analysis of the functional relationship between antigen-dependent and antigen-independent pathways of human T cell activation.

Previous data indicated that T lymphocyte activation can be achieved by using a combination of anti-T11 monoclonal antibodies (mAb) directed to the "T11(2)" and the "T11(3)" epitopes, respectively. Unlike the T cell activation induced by antibodies directed to the T3-T cell receptor (Ti) complex or to T44 molecules, the anti-T11 mAb-induced cell activation was not accompanied by surface modulation of the T11 antigen. In the present study we show that appropriate stimulatory combinations of anti-T11 mAb are able to induce T11 antigen modulation in a variety of T cells including polyclonal peripheral blood populations, normal as well as leukemic (JA3) T cell clones. The first anti-T11 mAb combination leading to both cell activation and T11 antigen modulation was given by a mAb directed to the T11(2) epitope and by another mAb recognizing an epitope belonging to the T11(1) group. The second combination was given by two mAb directed against two different determinants of the T11(1) group. The ability to induce T11 antigen modulation allowed a more precise analysis of the pathway of T cell activation initiated by T11 molecules and its physical and functional relationship with the other known pathways of T cell activation. T cells following T11 antigen modulation failed to respond to subsequent stimulation with anti-T11 mAb. The refractory period lasted for 48-72 h and the restoration of the responsiveness to anti-T11 mAb coincided with the re-expression of T11 molecules at the cell surface. Modulation of T11 antigen did not affect the surface expression of T3, Ti or T44 molecules, in addition, "modulated" cells maintained their ability to respond to mAb directed against T3, Ti or T44 molecules. On the contrary, antibody-induced modulation of the T3-Ti receptor complex abrogated both T11- and T44-dependent T cell activation. Finally, antibody-induced modulation of T44 antigen did not inhibit either the T11- or the T3-Ti-dependent pathway of T cell activation. These data indicate that down-regulation of the pathway of T cell activation initiated by T11 molecules can be induced not only by modulation of the antigen receptor complex but also by appropriate mAb to T11 molecules and, presumably, by the natural ligand binding to T11 molecules.

Antibodies, Monoclonal↗
PubMed1986

Identification of an early expressed marker of the luminal membrane of rabbit small intestinal columnar cells. Presence of a homologous antigen in kidney proximal tubules and glomeruli.

Four monoclonal antibodies have been produced that specifically react with a rabbit intestinal brush-border glycoprotein which migrates in SDS-polyacrylamide gel electrophoresis as a protein of molecular weight 140,000. Contrarily to brush-border hydrolases, it is expressed in poorly differentiated crypt cells of the small intestine. Absent from colon columnar cells, it can be considered to be an early marker of differentiation of absorbing cells of the small intestine. Immunofluorescence technique showed the presence of a homologous antigen in kidney proximal tubule brush-border and podocytes of kidney glomeruli.

Animals↗
PubMed1985

T-lymphocyte subpopulations identified by monoclonal antibodies after human bone-marrow transplantation.

Peripheral T-lymphocyte reconstitution after bone-marrow transplantation, 12 allogeneic and 13 autologous, was studied by indirect immunofluorescence assay using mouse monoclonal antibodies. Abnormal counts were detected in the two major sub-populations of T-cells i.e. helper and T cytotoxic-suppressor lymphocytes, defined by monoclonal antibodies (alpha Leu 3a and B 9.2), and in DR antigen-positive T-cells. The pattern of T-lymphocytes replenishment was identical for both types of transplant, and was not affected by Graft Versus Host disease (GVHD).

Antibodies, Monoclonal↗
PubMed1984

Flow cytometry is a new method for the characterization of intestinal plasma membrane.

The highly differentiated plasma membrane of rabbit enterocytes constitutes an interesting model for membrane studies. Flow cytometry allows combined measurements of the size of membrane vesicles by light-scatter and fluorescence polarization at a single-particle level. The degree of fluorescence polarization of 1,6-diphenylhexa-1,3,5-triene was determined at 4, 18 and 37 degrees C in the brush-border and basolateral plasma membranes. The fluorescence polarization was considerably higher in brush-border than in basolateral membranes. After incubation with dimethyl sulphoxide, the membrane fluidity decreased in both types of membranes. Moreover, a time-effect study of dimethyl sulphoxide showed changes in fluorescence polarization. Only in brush-border membrane a temporary fluid phase was observed. The different properties of the two membrane domains in relation to the lipid-protein dynamics of enterocytes are discussed.

Animals↗