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U Blank

Publications and source records attributed to U Blank.

44 records · Page 3Linked to original sources
PubMed1986

Size and charge heterogeneity of murine IgG-binding factors (IgG-BF).

Size and charge of murine IgG-binding factors (IgG-BF) were determined. Four different sources were used to produce the factors: a) cells of a T cell hybrid (T2D4) constitutively secreting IgG-BF upon incubation in serum-free medium, b) T2D4 cells incubated with mouse monoclonal IgG1 antibody in order to induce in vitro the production of isotype-specific IgG1-BF, c) T2D4 cells induced in vivo by passage as ascites in nude mice and incubated in serum-free medium, and d) in vivo alloantigen-activated T cells (ATC) incubated in serum-free medium. IgG-BF were affinity purified on Sepharose beads coated with rabbit or mouse IgG and identified by their biologic activities, i.e., inhibition of in vitro secondary IgG antibody production to SRBC and inhibition of rosette formation between Fc gamma receptor-positive spleen cells and rabbit IgG-sensitized erythrocytes. IgG-BF produced by either of these cell sources was found to be heterogeneous in both size and charge. In each case, IgG-BF activities were recovered in three fractions of apparent Mr-74,000 to 78,000, 35,000 to 40,000, and 19,000 to 23,000-and in four fractions of pI-4.7 (or 5.3, depending on experimental conditions), 6.5, 7.7, and 8.4. Moreover, IgG-BF translated in vitro from T2D4 poly A RNA by using rabbit reticulocyte lysate exhibited the same heterogeneity. Thus, IgG-BF contain different proteins exerting similar biologic activities.

Animals↗
PubMed1986

2.4G2, a monoclonal antibody to macrophage Fc gamma receptors, reacts with murine T cell Fc gamma receptors and IgG-binding factors.

In order to determine whether T cell Fc gamma receptors (Fc gamma R) and IgG-binding factors (IgG-BF) are structurally related, we searched for common antigens on these molecules. We found that the anti-macrophage Fc gamma 1/gamma 2bR monoclonal antibody 2.4G2 binds to similar determinant(s) on the macrophage-like J774 cells and on the Fc gamma R+ hybridoma T cells T2D4. On the T cell membrane, these determinants are associated with Fc gamma 1/gamma 2bR. They are absent on Fc gamma R- hybridoma T cells or the FcR- BW5147 thymoma cells. 2.4G2-reactive molecules were also detected in soluble material either extracted or released in the supernatant of Fc gamma R+ hybridoma T cells. 2.4G2-reactive molecules released in the supernatant of T2D4 cells could be absorbed on Sepharose beads coupled to rabbit IgG and they were recovered by acid elution. Conversely, Sepharose beads coupled to 2.4G2 retained molecules which had affinity for rabbit IgG, which suppressed an in vitro antibody response and which had the same molecular weight as IgG-BF. These results indicate that T cell Fc gamma R and IgG-BF share common epitopes and that 2.4G2 can serve as an anti-IgG-BF antibody.

Animals↗
PubMed1978

[Induction of immune tolerance to protein antigens in mice by 6-mercaptopurine (author's transl)].

The tolerance induction in mice to human serum albumin (HSA) and bovine gamma globulin (BGG) by combined injections of antigen and 6-mercaptopurine is studied. After pretreatment with antigen and mercaptopurine specific unresponsiveness or hyporesponsiveness are observed both in inbred (CBA) and outbred mice. Under the experimental protocol HSA is more tolerogenic than BGG. In CBA-mice tolerance to BGG was only found on the level of IgG-antibodies. The factors which influence the development of a drug-induced immunological unresponsiveness (mice strain, quality of antigen and antigen dosage) and the role of test system are discussed.

Animals↗
PubMedDate not supplied

The role of carbohydrates in the IgG binding and suppressive activities of shed human Fc receptors.

IgG Fc receptor (Fc gamma R) shed from human peripheral mononuclear cells and purified by IgG affinity chromatography bound to ConA, Pisum sativum, Ulex europeus and peanut lectins. The soluble Fc gamma R was not absorbed by wheat germ, soyabean, lentil, Sophora japonica or Helix pomotia lectins. Out of 14 different sugars, none interfered with the interaction between IgG Fc and membrane Fc gamma R. These results show that shed Fc gamma R had glucosyl, mannosyl, fucosyl and galactosyl groups, but that these components were not part of the IgG-binding site(s). The shed FcR had IgG-binding factor (BF) activity; it suppressed secondary in vitro antibody production. In accordance with the binding studies, IgG-BF activity could be adsorbed by ConA and PNA, but not by lentil lectins. The presence of 10 mM galactose or alpha-methylmannoside had no influence on biological activity, suggesting that, although present on human shed Fc gamma R, these sugars do not play a major role in its suppressive activity.

Antibody Formation↗