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M Colombatti

Publications and source records attributed to M Colombatti.

At least 55 records · Page 3Linked to original sources
PubMed1986

Immunotoxins show rapid entry of diphtheria toxin but not ricin via the T3 antigen.

We compared immunotoxins made with ricin and diphtheria toxin (DT) and with two monoclonal antibodies against different T cell-specific antigens, CD5 (T101) and CD3 (UCHT1). Only one reagent, UCHT1 linked to DT (UCHT1-DT), had exceptional properties. UCHT1-DT killed human peripheral T cells and T leukemia cells (Jurkat) at 2 to 10 pM, a concentration 10- to 100-fold lower than UCHT1-ricin and 10 to 500 times lower than native DT. The toxicity was blocked 50- to 100-fold by excess UCHT1 antibody. Human multipotent stem cells were not killed at up to 2000 pM UCHT1-DT. UCHT1-DT shows greater selectivity between T cells and stem cells than UCHT1-ricin, and may better prevent graft-vs-host disease in allogeneic bone marrow transplantation. The kinetics of UCHT1-DT were extremely rapid. UCHT1-DT inhibited Jurkat cell protein synthesis faster than DT and had a different ratio of lag time to inactivation rate. UCHT1-DT killed 90% of Jurkat cells within 2 hr at concentrations nontoxic to human stem cells. In contrast, UCHT1-ricin required more than 18 hr to kill one log of Jurkat cells. Another monoclonal antibody, T101, against the 65 kD CD5 antigen on Jurkat cells was linked to DT and ricin, and was compared with the UCHT1 immunotoxins. UCHT1-DT was 100 times more potent and five to 10 times faster than T101-DT and T101-ricin. Standardization to other antibodies with regard to the number of molecules bound per cell shows that UCHT1-DT is 10 to 100 times faster than previously reported immunotoxins. The role of the T3 antigen in transporting DT to the cytosol is discussed.

Antibodies, Monoclonal↗
PubMed1985

Sensitivity of target cells to immunotoxins: possible role of cell-surface antigens.

In this paper, we describe the activity of conjugates constituted of monoclonal antibodies chemically coupled to ricin and the ricin A-chain-like toxin gelonin. Several antibody-toxin conjugates (immunotoxins) were assayed against a Thy 1.2+ and Lyt 2.2+ T-cell line. Anti-Thy 1.2-gelonin and anti-Lyt 2.2-ricin immunotoxins (IT) had a good cytotoxic activity against target cells, whereas anti-Lyt 2.2-gelonin showed weak or no cytotoxicity. An anti-Lyt 2.2-gelonin IT displayed detectable cytotoxicity only when cells were pretreated with ammonium chloride. IT binding activity was very similar for anti-Thy 1.2 and anti-Lyt 2.2 IT, and surface antigen density was of the same order of magnitude for Thy 1.2 and Lyt 2.2 antigens. Our results suggest that intrinsic properties of the surface target antigen are able to influence the IT cytotoxic efficacy.

Animals↗
PubMed1984

Thy 1.2+ leukemia cells eradicated from in vitro leukemia-bone marrow cell mixtures by antibody-toxin conjugates.

A conjugate constituted by a monoclonal anti-Thy 1.2 antibody chemically coupled to the toxic subunit of ricin was synthesized. The conjugate was specifically cytotoxic for Thy 1.2+ (EL 4) but not for Thy 1.2- (BW5147) thymoma cells. In vitro treatment of bone marrow-leukemia cell mixtures (10:1 and 1:1 bone marrow to EL 4 cell ratios) with anti-Thy 1.2-ricin A chain totally eradicated EL 4 tumor cells, while the number of myeloid colony-forming units and pluripotent colony-forming units developed in vitro and in vivo was unaffected, which suggested that the treatment had no toxic side effects at least on the precursor cells examined.

Animals↗
PubMed1983

Selective killing of target cells by antibody-ricin A chain or antibody-gelonin hybrid molecules: comparison of cytotoxic potency and use in immunoselection procedures.

Ricin A chain and gelonin, two plant proteins that can powerfully reduce the protein synthetic capacity of ribosome preparations, were covalently coupled to a monoclonal anti-Thy-1.2 antibody. Two conjugates were prepared by using N-succinimidyl-3-2(-pyridyldithio)propionate, which generates a disulfide linkage between the component molecules. Both conjugates specifically killed Thy-1.2 antigen-bearing EL-4 cells, but had no effect on Thy-1.2- BW5147 cells. The cytotoxic potency of both reagents was determined by comparing the cloning efficiency of E1-4 target cells after treatment with the conjugate. The frequency of cells surviving treatment with 45 micrograms/10(6) cells of the gelonin conjugate was 1/72, whereas this frequency was 1/836 after exposure to 7 micrograms of the Ricin A chain conjugate. Both reagents could be successfully used to select Thy-1.2- cells from cell mixtures consisting of Thy-1.2+ and Thy-1.2- cells.

Animals↗
PubMed1982

An efficient method for purification of human T-cell growth factor.

A 1000-fold purification of human T-cell growth factor (TCGF) was achieved starting from supernatants of human spleen cells stimulated with phytohaemagglutinin (PHA) in culture medium containing 0.5% serum. The purification scheme involved precipitation with ammonium sulphate, gel filtration and blue-Sepharose chromatography. The use of polyethylene glycol 6000 (PEG 6000) was critical during the chromatographic steps in order to obtain high final recoveries or activity (40-50%). Purified preparations of TCGF labelled with 125I by the chloramine T method revealed that the activity co-migrated with 2 molecular species of 14,000-17,000 daltons in SDS-PAGE under non-reducing conditions.

Animals↗
PubMed1982

Modulation of human B-lymphocyte receptors for IgG does not affect HLA-DR antigens.

Receptors for the Fc portion of immunoglobulin G (Fc gamma R) on the surface of human peripheral T cells can be modulated on contact with antigen-antibody immune complexes (IgG-IC). Our results demonstrate that the Fc gamma R present on the surface of human B cells are also modulated on exposure to IgG-IC. Furthermore, the expression of HLA-DR molecules is not affected by the IgG-IC induced disappearance of Fc gamma R. In fact, the percentage of HLA-DR-positive cells and the relative amount of HLA-DR molecules on individual B cells analysed by flow microfluorometry was shown not to be influenced by Fc gamma R modulation. Moreover, pretreatment of cells with monoclonal antibodies directed against non-polymorphic determinants of HLA-DR antigens did not prevent the binding of IgG-coated ox erythrocytes. These results argue against a structural relationship between Fc gamma R and HLA-DR molecules on the surface of the B-cell populations investigated here.

Antibodies, Monoclonal↗
PubMed1981

Human T lymphocytes subpopulation as defined by alloantigens and FC receptors a comparative analysis.

Human peripheral T cells were fractionated in accordance to their surface receptors for G or M immunoglobulins and analyzed for their reactivity with alloantisera obtained by planned immunization involving HLA-A and HLA-B compatible individuals. These alloantisera were previously shown to recognized polymorphic structure exclusively expressed on T cells. Although the majority of the alloantisera analyzed reacted with different proportions of both T(M) and T(G) populations, some antisera specifically recognized surface structure restricted to either T(M) or T(G) lymphocytes. The various alloantisera consistently reacted with a fraction only of T(G) and T(M) cells, this indicating that these T cell subsets can be further fractionated in accordance to the expression of the alloantigenic determinants recognized by these antisera.

Animals↗
PubMed1981

Fc receptors on human T lymphocytes: loss of Fc mu and expression of Fc gamma receptors by T cells stimulated in mixed lymphocyte reaction.

The consequences of allogeneic stimulation on the expression of Fc mu or Fc gamma receptors were analysed in T-cell populations responding in mixed lymphocyte reaction (MLR). Unfractionated T-cell populations were cultured with a pool or irradiated allogeneic T-depleted cells. The responder E-rosetting cells progressively lost Fc mu and acquired Fc gamma receptors. The change of the original Fc receptor phenotype is not the consequence of a preferential proliferative response of TG versus TM cells but is likely due to a de novo expression of Fc gamma receptors by T cells lacking detectable Fc receptors (T-null) and also to the loss of Fc mu and expression of Fc gamma receptors by TM cells. These data suggest that, after MLR, responder T cells can modify their Fc receptor phenotype.

Animals↗
PubMed1981

B lymphocytes in newborns.

B lymphocyte markers in 24 full term newborn infants were evaluated within four days after birth. It was demonstrated that the percentage of cells with surface immunoglobulins (SmIg) in the blood of these subjects was normal when the lymphocytes were stained with polyvalent as well as monospecific antisera. The percentage of cells bearing Fc receptors were found to be slightly, but not significantly, reduced. The ability of newborn lymphocytes to form rosettes with mouse erythrocytes was significantly reduced. The hypothesis that the B dependent system reaches complete maturity already at the first days after birth is discussed.

Animals↗
PubMed1981

Human spleen as a source of T cell growth factor.

Human spleen cells were tested for the ability to produce T cell growth factor (TCGF) upon stimulation with PHA. Quantitative analysis of the amounts of TCGF produced under optimal conditions indicated that supernatants obtained from spleen cell cultures were approximately five times more active than those derived from peripheral blood leucocytes (PBL). Moreover, in contrast to PBL, there was no significant difference in TCGF production between individual spleen cell populations. Among splenic T cells, TG-depleted cell fractions were superior to TG-enriched cell fractions in producing TCGF upon PHA stimulation. These supernatants induced intense proliferation of blast cell populations isolated from mixed leucocyte-tumour cell cultures (MLTC) established with PBL and irradiated allogeneic myelogenous leukaemic cells. Within 7 days of culture in TCGF, the number of MLTC blast cells increased approximately 300-fold. Concomitantly, the lytic activity (on a per-cell basis) of these populations against the corresponding myelogenous leukaemic cell targets increased approximately 80-fold.

Cell Survival↗
PubMed1981

Distribution and properties of Fc receptors for IgG on different leucocyte populations in man.

The distribution and some characteristics of Fc receptors for immunoglobulin (Fc gamma R) were analysed on different human leucocyte populations. Interaction of Fc gamma R present on T gamma cells with ox erythrocytes-IgG immune complexes (IgG-IC) provides a switch-off signal for the expression of the Fc gamma R themselves; in addition, these receptors are sensitive to the proteolytic activity of pronase. Since both of these phenomena could have important effects on certain functional activities of the cells, we have analysed the effect of the interaction between IgG-OxE and the Fc gamma R present on various leucocyte populations. The large majority of T gamma cells or of tonsil B cells lost their Rc gamma R after interaction with IC; IC, in turn, had no effect on the Fc gamma R of AC and PMN. Twelve to 22% of the non-T, non-AC fractions retained surface Fc gamma R. Enzymatic treatment of the cells showed that T cells, non-T, non-AC and B cells have Fc gamma R sensitive to pronase, whereas Fc gamma R present on AC and PMN are resistant even to very high concentrations of the enzyme.

Antigen-Antibody Complex↗
PubMed1980

T cell immune function in newborn infants.

T cell immune function in 20 newborn infants was investigated. Previous studies showing increased spontaneous transformation and higher 3H-thymidine incorporation at lower PHA concentration in newborn infants were confirmed. A net increase in the number of active E rosette-forming lymphocytes and a slight decrease in the percentage of total E rosette-forming cells was also found. Our results suggest the presence of a subpopulation of activated T lymphocytes in the peripheral blood of newborns during the first days of life. Possible mechanisms of this activation are discussed.

Adult↗
PubMed1979

Imbalances of T cell subpopulations in patients with atopic diseases and effect of specific immunotherapy.

Reduced numbers of T cells with Fc receptors for IgG (TG cells) are present in blood samples of patients with respiratory allergic disease, mainly those with severe symptoms. TG cells have been previously shown to be suppressor in the pokeweed mitogen- (PWM) dependent B cell differentiation. T cells with Fc receptor for IgM (TM cells), which help immunoglobulin production, are in a normal range. After specific hyposensitization, resulting in a sharp improvement of clinical symptoms, TG cell subset reached normal values.

Adolescent↗
PubMed1979

Immunological features in chronic lymphocytic leukaemia (CLL) of T cell origin.

Peripheral blood lymphocytes from a patient with chronic lymphocytic leukaemia of T cell origin were studied. The thymus derived nature of these lymphocytes was confirmed by surface markers, mitogen cultures, mixed lymphocyte reaction, cytotoxicity studies, and cytochemical stains. This case is notable for several clinical and laboratory findings. Among these, the benign clinical course, the reduced rate of serum immunoglobulins, the elevated number of active E rosettes, the increased PHA-induced response to low mitogen doses, the absence of PHA mediated cellular cytotoxicity, and the thy-like positivity to ANAE should be pointed out. Emphasis should be placed, however, on the loss of stimulatory ability in MLR. This last feature supports the hypothesis that these cells proliferate as a clone.

Aged↗
PubMedDate not supplied

Effect of therapeutic macromolecules in spheroids.

Recent advances in biotechnology have allowed the production of new types of macromolecular therapeutic agents (antibodies, immunotoxins, cytokines, extracellular matrix molecule (ECM) proteins, vectors) that may eventually find broad clinical applications in the treatment of human tumors and other diseases. The model of the Multicellular Tumor Spheroids (MTS) represents a valuable tool to test the therapeutic potential of these new pharmacologic agents in a 3-D context. Specific questions pertaining to the behaviour in a 3-D setting of some of the macromolecules under evaluation for in vivo applications can also be addressed in the MTS model (e.g. 'binding site barrier', role of cell-cell and cell-ECM interactions). This paper reviews the most significant contributions regarding the delivery of macromolecules to MTS, the penetration and therapeutic effects of antibodies, radiolabelled antibodies, immunotoxins and other macromolecular compounds.

Antineoplastic Agents↗