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D Fradelizi

Publications and source records attributed to D Fradelizi.

At least 91 records · Page 5Linked to original sources
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

Modification of T-cell proliferation and interleukin 2 production in mice infected with Trypanosoma cruzi.

Acute infection of mice with Trypanosoma cruzi results in severe immunodepression and the appearance of autoimmune symptoms. In vitro, concanavalin A-stimulated T cells from spleens of infected animals could neither produce nor respond to interleukin 2. Interleukin 2 production was not restored by addition of exogenous interleukin 1, and proliferative response to concanavalin A was not restored by exogenous interleukin 2. A population of Thy-1-negative cells in the spleen of infected animals was shown to suppress the concanavalin A proliferative response and, to a lesser extent, the production of interleukin 2. These and other symptoms of T. cruzi-infected mice are similar to the immune dysfunction of autoimmune lpr/lpr mice. These findings are discussed in relationship to the pathology of Chagas disease.

Animals↗
PubMed1983

Leukemia cell lines can replace monocytes for mitogen-induced T-lymphocyte responses: this accessory function is dependent upon their differentiation stage.

Highly purified peripheral T lymphocytes do not proliferate in response to phytohemagglutinin A or concanavalin A, unless adherent HLA-DR+ monocytes are added as accessory cells. The accessory function (AF) of monocytes is mediated through the release of interleukin-1 (IL-1). We here report that cells from three human leukemic lines--K562, HL-60, and U-937--could exert AF and efficiently replace monocytes in a 72-hr mitogen-stimulated proliferation assay. This AF was clearly related to precise maturational stages of these cells, since the hematopoietic precursor K562 cells spontaneously exerted high AF but lost this property when treated with differentiation inducers such as sodium butyrate or phorbol 12-myristate 13-acetate (PMA). On the other hand, untreated HL-60 and U-937 cells exhibited no spontaneous AF, but they acquired this function when induced to differentiate either along the granulocytic pathway (dimethyl sulfoxide-treated HL-60 cells) or along the monocytic pathway (PMA-treated HL-60 and U-937 cells). Supernatants from PMA-triggered K562 or HL-60 cells allowed the proliferative response of murine thymocytes to phytohemagglutinin A and were therefore shown to contain IL-1. Analysis of phenotypical markers showed that AF and IL-1 production were not restricted to cells of the monocytic lineage. No HLA-DR antigen could be detected on K562 and HL-60 cells. Thus, the expression of HLA-DR antigens is not required for AF and IL-1 production in response to mitogens. Human leukemia cell lines could provide useful sources of human IL-1.

Cell Differentiation↗
PubMed1983

Inhibiton of IL 2 production after human allogeneic bone marrow transplantation.

Bone marrow transplantation (BMT) is currently used to treat patients with severe aplastic anemia or leukemia. Despite the use of an HLA identical sibling donor, however, the survival after BMT is reduced by the occurrence of two major immunologic complications: graft-vs-host disease and a long-lasting immune deficiency responsible for late infections. This immune deficiency could be explained by an imbalance of lymphocyte subpopulations reconstituted after transplant. The aim of the present work was to study the helper function by measuring the production of interleukin 2 (IL 2). This lymphokine is responsible for the amplification of the effector phase of immunity. A consecutive series of 34 patients was tested for IL 2 production after BMT. This production was absent or low in 32 of 34 patients for at least 2 yr after BMT. The mechanism of this low IL 2 production was investigated. Irradiation of patients' lymphocytes in vitro with low dose gamma-rays partially restored the IL 2 production after 6 mo of evolution. The IL 2 production was not restored or was slightly affected by irradiation early after BMT. These results suggest that the lack of immune reconstitution after BMT may be caused by the lack of IL 2-producing cells and/or the increased activity of suppressor cells of the helper function. This suppression is radiosensitive.

Bone Marrow Transplantation↗
PubMed1982

[Polymorphism of HLA genes: I. Demonstration of a close correlation between DNA fragments determined by BglI restriction enzyme and HLA class I antigens].

Description of DNA fragments associated to HLA class I gene is possible by using restriction enzymes which determine these fragments and specific DNA probes which permit their detection. In one family, with a child presenting a recombination between HLA-A and C, six fragments determined by the enzyme BglI were found to be polymorphic. The informative fragments segregate with HLA, either with a whole haplotype or with one of the two recombinant segments of the HLA complex. In a small sample of population they correlate with one (A11) or with a group of known cross-reactive antigens serologically defined (A3 and A11; A25 and A26. Another fragment is associated with unknown cross-reactive antigens (A2 and A29).

DNA↗
PubMed1982

[Cellular regulation of human interleukin-2 production].

The mechanism of IL2 production by T lymphocytes has been clearly established in Mice. Previous studies have also suggested that control of IL2 production is similar in the Human. We have observed that a complete depletion of adherent monocytes abrogates IL2 production by T lymphocytes. On the other hands in humane inhibition of IL2 production was also mediated by an excess of monocytes. This inhibition was mediated by soluble products and could be blocked by treatment with indomethacin. PGE2 was identified as one of this, inhibitory monokine. A possible mechanism of this inhibition by PGE2 is suggested. Such inhibition was not observed if the T lymphocyte suspension was irradiated (1000 rad) before addition of PGE2 or excess monocytes. These results suggest that activation of a radiosensitive T cell by monokines is required for the inhibition of IL2 production. A model for the cellular control of human IL2 production is proposed.

Cell Adhesion↗
PubMed1982

Interferon inhibits the generation of allospecific suppressor T lymphocytes.

The effect of human interferon alpha on the differentiation of functional populations of lymphocytes during the human allogeneic response in vitro was studied. Interferon alpha inhibited the generation of allospecific suppressor T lymphocytes that normally develop from lymphocytes primed in vitro against allogeneic cells. This effect was not the result of the destruction by interferon of precursor suppressor cells but rather to inhibition of their differentiation into active suppressor T lymphocytes. This inhibition was reversible and could be overcome by repeated allogeneic stimulation even in the presence of interferon. Inhibition of the generation of allospecific suppressor lymphocytes by interferon might play an important role in the allogeneic response. Interferon inhibited the proliferation of lymphocytes after allogeneic stimulation in a primary mixed lymphocyte reaction but enhanced their cytotoxicity. Despite the inhibitory effect in the primary mixed lymphocyte reaction, the specific secondary proliferative response of lymphocytes primed against a single HLA-DR antigen was only slightly affected by interferon. On the other hand, the nonspecific secondary proliferative response of lymphocytes primed in the presence of interferon was significantly reduced, indicating that interferon might decrease the recruitment of nonspecific "irrelevant" clones of responding cells during the sensitization period.

Cytotoxicity, Immunologic↗
PubMed1981

[Suppression of proliferative allogenic response in patients receiving a programmed series of transfusions prior to renal graft].

The effects on the lymphocytic proliferative allogenic response of a protocol of planned blood transfusions have been studied in 12 patients with chronic renal failure. This study was prospective and the experiments were performed before kidney grafting. The results were then compared with the clinical results of the graft. These results have shown that the peak allogenic proliferation in the group of patients with good renal function was significantly decreased after transfusion. This decreased response was not observed in the groups of patients with either kidney rejection or immunisation and antibody formation. Most of the lymphocyte suspensions whose proliferation was decreased after transfusion were also capable of inhibiting the proliferation of autologous lymphocytes taken before transfusion. It is therefore legitimate to postulate that the decreased response was due to the generation of suppressor lymphocytes. This latter could be responsible for the beneficial effects of blood transfusion on kidney grafting.

Blood Transfusion↗
PubMed1980

[Kinetics of the appearance of HLA-DR antigens on human alloactivated T lymphocytes and the demonstration of new antigenic determinants].

By studying serologically the appearance of HLA-DR determinants on T lymphocytes activated by a mixed lymphocyte culture, we have been able to demonstrate the existence of a new class of antigenic determinants distinct from classical HLA-DR antigens. Indeed, some monospecific anti-DR sera were cytotoxic from some alloactivated T cells, though not directed against their HLA-DR specificity. The absorption of these anti-sera on B lymphocytes bearing the HLA-DR antigen against which they were directed, did not remove their reactivity on alloactivated T lymphocytes. The absorption of the same anti-sera on activated T lymphocytes did not affect their anti-DR reactivity. This study shows the existence of new antigenic determinants expressed by T lymphocytes during their activation: alloactivated T lymphocyte antigens (AATL).

Cells, Cultured↗
PubMed1980

[Mode of action of a soluble restricted factor, a suppressor of the allogeneic proliferative response in man].

Appearance of "suppressor cells" is induced by in vitro hyperimmunization of lymphocytes against allogeneic cells, incompatible for one HLA-DR antigen. These "suppressor cells under certain conditions, release in the culture medium, "suppressor factors" of the in vitro allogeneic proliferative response in Man. They are not immunoglobulins and act in a non specific way towards the stimulators. Only one of them is restricted to some individuals. This is shown when either responders or stimulators are incubated for different periods, with the "suppressor factors" prior to the primary mixed lymphocyte reaction (MLRI). The beneficial effect of transfusions on kidney graft survival, could be, in part, explained by a suppressor mechanism, analogous to the one described in vitro.

Cell Division↗
PubMed1980

Suppression of the human allogenetic response in vitro with primed lymphocytes and suppressive supernates.

Human lymphocytes primed in vitro by allogeneic cells develop lymphocyte populations with different functions. Cells with a memory of the allogeneic contact and cytotoxic effectors have been identified previously. We now report on a third lymphocyte population generated by repeated in vitro sensitization. This is of suppressor lymphocytes that can inhibit the primary proliferation of unsensitized lymphocytes. Our experiments indicate that these human suppressor cells are most probably T lymphocytes, adherent to glass or nylon wool, and radioresistant. They derive from both the large blast cells and the small, nondividing lymphocytes that are observed on day 7 of the allogeneic response. The suppressor cells release suppressor factor(s) upon restimulation. Studies on the specificity of the suppression have shown that suppressor cells are specific to the HLA-DR antigens presented by stimulator lymphocytes and that they probably release the suppressor factor only when confronted with the specific HLA-DR antigen. However, when the suppressor factor is produced, the proliferative response to any stimulating cell is inhibited regardless of its HLA-DR antigens. On the other hand, the suppressor factor can only suppress the proliferation of lymphocytes from some individuals. This restriction suggests that suppression can only occur when the producer of the suppressor factor and the responding lymphocytes that are being tested, have some identities in common. No evidence in favor of an HLA-D restriction has been obtained so far.

Cell Adhesion↗
PubMed1980

Functional study and detection of HLA-D products on fractionated human bone marrow cells.

Bone marrow cells from nine normal human volunteers obtained from the Iliac crest, were used in this work for antigen determination and functional studies. The bone marrow aspirated cells were sequentially separated: elimination of erythrocyte, granulocytes and monocytes achieved by Ficoll-Isopaque centrifugation followed by plastic adherence. Purified bone marrow cells were finally separated by size using velocity sedimentation. The slow sedimenting small cells were shown to be mainly T lymphocytes, probably of blood origin. The medium sized bone marrow cells were shown to contain myeloid precursors (CFu-c). Large immature cells were in cycle actively synthesizing DNA molecules. HLA-D and HLA-DR detections on the fractionated cells were performed using three techniques: fluorescence with specific anti HLA-DR allo and xeno antisera; primed lymphocyte typing (PLT) with anti HLA-DR monospecific in vitro primed lymphocytes and detection of the HLA-D stimulating product using the bone marrow fractionated cells as stimulators in a mixed leukocyte culture. Concordant results were obtained with the three techniques. Lymphocytes in the bone marrow express HLA-D products a peripheral lymphocytes. Bone marrow fractions depleted of lymphocytes and monocytes also contain approximately 20% of cells expressing HLA-D products The meaning of the expression of HLA-D products on immature precursors non-lymphoid cells is discussed.

Bone Marrow Cells↗
PubMed1980

[Suppressor cells and factor of the allogeneic proliferative response in man].

During multiple in vitro allosensitisations of human lymphocytes, suppressor cells of the allogenic response are developed. They are radioresistant and specific to the HLA-DR presented by the stimulators, and adherent to nylon and glass wool, while cytotoxic cells are not. Moreover when irradiated, these hyperimmunized cells are able to release a suppressor factor (SF). This suppressor factor is non antigen specific and active on the autologous producer and some allogenic responders. There is a restriction phenomenon, the genetic control of which is not yet defined. The dominant effect of multiple transfusions on kidney graft survival could be explained in part by a similar cellular mechanism.

Cell Division↗
PubMed1980

Different stimulating capacity of B and T lymphocytes in primary and secondary allogeneic reactions: cellular detection of HLA-D products on T lymphocytes.

The present study was undertaken to define the best way to produce and to test primed lymphocyte typing (PLT) cells using B- and T-enriched lymphocyte suspensions. Intrafamilial PLT cells were produced with primed unseparated and T purified lymphocytes against haplo-identical donors' T and B cells. These PLT cells were then restimulated with a panel of related or unrelated individuals' T and B cells and with allogeneic in vitro activated T cells. The best discrimination was obtained when PLT reagents, regardless of the production method, were restimulated by a B-enriched population of peripheral lymphocytes. Furthermore, the results have shown that enriched primed or unprimed T cell suspensions stimulated by enriched T lymphocytes did not give any proliferation. Experiments performed to explain the results led us to distinguish 2 different phenomena: in primary cultures, the addition of monocytes autologous to the responder cell restored the proliferation of enriched T cells stimulated by T lymphocytes. In secondary cultures, the addition of monocytes autologous to the PLT cell did not restore the proliferation of PLT lymphocytes stimulated by enriched T cells. This was shown to be due to the lack of Dr antigen on the stimulating cell: if allogeneically activated T cells were used as stimulating lymphocytes, a DR-specific proliferative response appeared. This correlates with serologic findings were DR determinants are found on activated T cells and not on unprimed T lymphocytes. However, this difference might be only quantitative, since peripheral lymphocytes could be primed by T cells and be DR specifically restimulated.

B-Lymphocytes↗
PubMed1979

[Demonstration of a soluble factor capable of inhibiting allogenic lymphocyte proliferation in man].

During the secondary mixed lymphocyte reaction (MLR), i.e. after the double in vitro allogenic sensitization between responding and stimulating cells bearing at least one HLA-DR incompatibility, suppressor cells are developed [1]. They are able to inhibit a primary MLR provided that the stimulating cells possess the same DR incompatibility as the immunizing cells. We report here that this inhibition is due to the production by these cells of a soluble suppressor factor which acts on responding cells provided that they share at least one gene product of the HLA-D region with the cells producing the factor. This a feedback process of auto-inhibition occurring after hyperimmunization. The action of this suppressor factor seems to be genetically restricted to an as yet unknown locus in linkage disequilibrium with HLA-DR.

Cell Division↗