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M M De Bracco

Publications and source records attributed to M M De Bracco.

13 recordsLinked to original sources
PubMed1985

Modification of the contractile activity of isolated rat atria by lectin-activated T-lymphocyte subsets.

We had previously shown that human T-lymphocytes (ERFC) that had been activated for a short time with phytohemagglutinin (PHA) produced positive inotropic and chronotropic effects on spontaneously beating rat atria (Sterin-Borda, L., et al., Naunyn Scmiedeberg's Arch. Pharmacol. 324, 58, 1983). In this study, we first prepared T4-rich (T4) and T8-rich (T8) cells from ERFC by selective lysis with OKT4 and OKT8 monoclonal antibodies and rabbit complement. Then, we tested the effect of PHA-stimulated T4 (PHA-T4) and T8 (PHA-T8) on beating rat atria. PHA-T4 cells stimulated the tension and the frequency of contraction of isolated rat atria by a mechanism that involved the generation of the slow reacting substance of anaphylaxis (SRS-A), since both 10(-5) M nordihydroguaiaretic acid (NDGA) and 10(-7) M FPL-55712 were effective inhibitors. On the other hand, PHA-T8 cells decreased the tension of beating atria. Indomethacin (10(-6) M) could not block the depressor effect. Cell-free PHA-T4 supernatants reacted with the heart tissue similarly to whole PHA-T4 cells. Since NDGA or FPL-55712 treated organs did not respond to active PHA-T4 supernatants, the lipoxygenase system of the auricles seems to be required for the reaction and the active metabolites appear to derive mainly from the heart. Our results suggest that PHA-activated "helper/inducer" cells release soluble factors that can in turn trigger the lipoxygenase metabolic pathway of arachidonic acid in the heart, generating the active leukotrienes responsible for the positive inotropic and chronotropic effects.

Animals↗
PubMed1976

Cell-mediated cytotoxicity. Characterization of the effector cells.

Isolated human mononuclear cells were fractionated according to their membrane characteristics or physical properties. Adherent cells were depleted by filtration through glass columns; phagocytic cells were removed by iron treatment and cell subpopulations capable of forming rosettes with sheep erythrocytes (E), erythrocyte-antibody-complement (EAC) and chicken erythrocyte-antibody complexes (CEA) were separated by centrifugation of Ficoll-Hypaque gradients. The functional activity of the cell subpopulations obtained was assayed by testing PHA-induced cytoxicity (PIC), antibody-dependent cytoxicity (ADCC) and blast transformation by PHA. The results of this study demonstrate that: (1) cells reacting in PIC and ADCC assays are different, adherent and phagocytic cells being necessary for full expression of PIC and not for ADCC; (2) PHA induces direct blast transformation of purified E-RFC in the absence of PIC cytotoxic cells; (3) cell populations specifically enriched in E or EAC rosette-forming cells are not cytotoxic neither in the PHA nor in antibody mediated cytotoxic assays; (4) cells participating in ADCC can be selectively purified by centrifugation of CEA rosettes.

Antibodies↗
PubMed1971

C1r, subunit of the first complement component: purification, properties, and assay based on its linking role.

A method to obtain C1r, a subunit of the first complement component, in a highly purified state has been described for the first time. The stepwise method starts with a neutral euglobulin precipitation, after diethylaminoethyl- and carboxymethyl-cellulose chromatography and a final preparative polyacrylamide electrophoresis step. Such C1r preparations are devoid of C1q and C1s activities and show only one protein band on analytic polyacrylamide electrophoresis. Rabbits injected with this preparation produced antisera showing only one precipitation band. The stability of C1r activity was determined under different conditions, and C1r was found to be labile at 37 degrees C, pH 7-8 and low ionic strength. The electrophoretic mobility of purified C1r is that of a beta-globulin on disc acrylamide electrophoresis and on agarose electrophoresis at pH 8.6. Its molecular weight as estimated by sephadex chromatography is 168,100.A sensitive hemolytic assay based on the property of C1r to link C1s to C1q and thereby to generate macromolecular C[unk]1 is described. The number of C[unk]1 molecules generated is stoichiometrically related to the concentration of C1r for a fixed C1q and C1s concentration provided that the titration is carried out below the plateau zone. Macromolecular C1 can be separated from free C1s as the former is cell bound. This method of purification and assay should allow the development of monospecific antisera and further chemical study of C1r.

Beta-Globulins↗
PubMedDate not supplied

Antibody-dependent cell-mediated cytotoxicity in rheumatoid arthritis. Effect of rheumatoid serum fractions on normal lymphocytes.

Reduced antibody-dependent cell-mediated cytotoxicity (ADCC) was demonstrated in lymphocytes of patients with rheumatoid arthritis (RA). Rheumatoid factor (RF) positive sera inhibited ADCC of normal lymphocytes by reacting both with effector and target cells (sensitized chicken red blood cells). These sera were fractionated by specific adsorption or gradient ultracentrifugation, and isolated RF or RF negative fractions were tested for their ability to inhibit ADCC by reacting with normal human lymphocytes or target cells. RF was ineffective on normal lymphocytes but it strongly inhibited the reaction by interaction with target cells. IgG RF negative fractions of certain sera were inhibitory by direct interaction with effector cells.

Antibodies↗