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Biomedical subjects

U Hadding

Publications and source records attributed to U Hadding.

At least 91 records · Page 5Linked to original sources
PubMed1977

Inherited polymorphism of guinea pig factor B and C4: evidence for genetic linkage between the C4 and Bf loci.

An inherited structural polymorphism of the guinea pig complement protein C4 and of factor B of the alternative pathway was demonstrated by use of high voltage agarose electrophoresis combined with a subsequent immunofixation technique. No polymorphism of guinea pig C3 could be shown. Three common allelic genes were proven to code for C4-S, C4-S1, and C4-F, respectively. Two common allelic genes are responsible for the Bf-F and Bf-S phenotype expression. A strong linkage disequilibrium between both C4 and Bf was demonstrated.

Animals↗
PubMed1977

Linkage of guinea pig Bf and C4 TO THE GPLA.

Inbred and partially inbred strains of guinea pigs were typed for their polymorphic Bf and C4 patterns. In crosses and backcrosses of inbred strains of guinea pigs the inheritance of Bf, C4, and GPLA phenotypes was studied. The presented data indicate linkage of the structural Bf and C4 loci to the major histocompatibility complex (MHC) of the guinea pig, the GPLA system. Evidence for a GPLA-B-Ia crossover was obtained. Bf and C4 typing contributes to the characterization of the GPLA region in some inbred strains thus providing a simple method for determining the state of inbreeding on the one hand and providing the necessary third or fourth region within the GPLA for the detection of informative meiosis, on the other.

Animals↗
PubMed1976

In vitro synthesis of factor B of the alternative pathway of complement activation by mouse peritoneal macrophages.

Factor B of the alternative pathway of complement activation was shown to be synthesized and secreted by unstimulated mouse peritoneal macrophages. The activity of B in the culture supernatants from macrophage monolayers was detected by consumption of C3 in reaction mixtures containing supernatant and guinea pig factors C3, D and insoluble C3b. Using a monospecific antiserum, factor B in concentrated culture supernatants was shown by immunodiffusion and immunoelectrophoresis to be identical to factor B in mouse plasma and to form a characteristic complex with cobra venom factor in the presence of D. A steady rate of factor B secretion was observed for 4 days providing the medium was changed every 24 h. Cycloheximide (0.5 mug/ml), an inhibitor of protein synthesis, caused inhibition (90%) of factor B production. Incubation of culture medium containing 14C-labeled amino acids with the macrophage monolayer resulted in incorporation of radioactivity into factor B as detected by autoradiography of precipitation lines formed with anti-B antiserum; This indicated that synthesis of factor B had occurred. In the same culture supernatants the presence of newly synthesized C3 was also demonstrated.

Animals↗
PubMed1976

Mouse factor B of the alternative pathway of complement activation. I. Purification, characterization, and functional behavior.

Mouse factor B was purified and a monospecific antiserum was raised. The physicochemical data of this protein (108,000 m.w., 5.9 S, 5.9 to 6.05 isoelectric point) were determined. The functional behavior resembles that of human and guinea pig factor B and it operates efficiently in the C3 feedback cycle of the alternative pathway of complement activation. A provisional scheme is given for the operation of the C3bB enzyme on the cellular (macrophage) level.

Animals↗
PubMed1975

Dextran sulphate: a synthetic activator of C3 via the alternative pathway. I. Influence of molecular size and degree of sulphation on the activation potency.

The polyanion dextran sulphate (DS) triggers the alternative pathway of complement. The influence of the molecular weight and degree of sulphation on this potency was studied. The degree of substitution turned out to be the critical parameter for optimal C3 turnover: 60 SO4/100 glucose units (Glc) showed optimal activity; an increase up to 190 SO4/100 Glc did not increase the activation potency, while lowering the degree of sulphation diminished this activity. DS preparations (120 SO4/100 Glc) of molecular weight: 1 x 10(4); 8 x 10(4); 2-5 x 10(5); 2 x 10(6) were equally active; a DS of molecular weight 5 x 10(3) was inactive. These results indicate that above a critical molecular size (greater than 5 x 10(3)) only the degree of substitution is responsible for the C3 activating capacity. Clusters of several glucose residues each carrying one or two sulphate groups are thought to be the essential structure in DS for the activation of the alternative pathway.

Animals↗
PubMed1975

Activation by some T-independent antigens and B cell mitogens of the alternative pathway of the complement system.

A number of T-independent antigens and B cell mitogens were examined for their ability to activate C3 via the alternative pathway of the complement system. Loss of hemolytically active C3, generation of anaphylatoxin activity, and immunoelectrophoretic conversion of C3 and factor B, were checked in normal and C4-deficient guinea pig serum, and, in some cases, in normal human serum. As judged by their activity in these assays, 10 lipopolysaccharides of different origin and constitution, pneumococcus type III polysaccharide, levan, dinitrophenylated aminoethyl-dextran, dinitrophenylated (D-glutamic acid, D-lysin) copolymer, polymerized flagellin, and pokeweed mitogen were all capable of initiating the alternative pathway, but differed with respect to their potency, their relative activity in the presence or absence of C4, and their ability to inhibit C3-turnover at high concentrations. Polyvinylpyrrolidone of intermediate molecular weight (4 x 10(4) daltons) was only active if the most sensitive assay was used (anaphylatoxin generation). Other species of polyvinylpyrrolidone, depolymerized pneumococcal polysaccharide, aminoethyl-dextran, [D-glutamic acid, D-lysin] copolymer, phytohemagglutinin and concanavalin A failed to activate C3. C3-consumption by concanavalin A was due to nonspecific binding.

Anaphylaxis↗
PubMed1975

Interaction of C3b, B, and D in the alternative pathway of complement activation.

The interaction of ZXd2, an insoluble intermediate of the alternative pathway on zymosan (Z5), with factor B and the enzyme D proceeds in a two-step reaction: 1) B binds in the presence of Mg++ to ZXd2 to form the intermediate ZXd2B, 2) B bound to ZXd2 is subsequently activated enzymatically by D to yield the complex ZXd2B which cleaves C3. Evidence was obtained that C3b, which is present on ZXd2, is required for ZXd2B formation. Studies of the functional role of C3b for ZXd2B formation revealed that C3b is involved in the first reaction step i.e., binding of B to ZXd2 to yield ZXd2B. Formation of ZXd2B is inhibited by pretreatment of ZXd2 with either anti-C3 Fab or with C3b-INA. Low ionic strength of about 2 mS was found to favor the interaction of the C3b with B. Mg++ concentrations from 1 to 31 mM as well as variation of pH in the range from 6.2 to 8.5 did not greatly influence the reaction of B with ZXd2. For the enzymatic activation of B only C3b on ZXd2 and factor D are required. This is concluded from the finding that fluid phase C3b is sufficient for the activation of B in the presence of D. This does not exclude the fact that other proteins present on ZXd2 may help to stabilize the intermediate ZXd2B or the enzymatically active complex AXd2B, or both of them.

Animals↗
PubMed1974

Complement-dependent B-cell activation by cobra venom factor and other mitogens?

It has been proposed that two distinct signals are required for the triggering of the precursors of antibody-forming bone marrow-derived cells (B cells): (a) the binding of antigen or of a mitogen to the corresponding receptor sites on B-cell membranes and (b) the interaction of activated C3 with the C3 receptor of B lymphocytes. There is growing evidence that B-cell mitogens and T (thymus-derived cell)-independent antigens are capable of activating the alternate pathway of the complement system (bypass). Therefore, the effect of another potent bypass inducer was investigated with regard to B-cell activation and the role of C3. Purified, pyrogen-free cobra venom factor was mitogenic for both T and B lymphocytes (cortisone-resistant mouse thymus cells and lymph node lymphocytes from congenitally athymic mice). Venom factor could substitute for T cells by restoring the potential of antibody formation to sheep red blood cells in mouse B-cell cultures supplemented with macrophages or 2-mercaptoethanol. Venom factor may be capable of conferring activated C3 to the C3 receptor of B lymphocytes: preincubation of lymphoid cells with homologous serum or plasma, 10 mM EDTA, and sepharose-coupled venom factor converted with serum to an enzyme active against C3, inhibited their capacity to subsequently form rosettes with sheep erythrocytes sensitized with amboceptor and C5-deficient mouse complement. In the absence of EDTA, preincubation of freshly prepared B-cell suspensions with C3-sufficient homologous serum also blocked their subsequent interaction with complement-sensitized erythrocytes and at the same time rendered them reactive to an otherwise T-cell-specific mitogen. Moreover, mitogen induced B-cell proliferation in lymph node (but not in spleen) cell cultures, appeared to depend on the availability of exogenous C3: zymosan-absorbed fetal bovine serum (only 8.3% site-forming units remaining) supported T-cell activation by phytohemagglutinin, concanavalin A, and venom factor, but failed to sustain B-cell stimulation by pokeweed mitogen, lipopolysaccharide, and venom factor. T-cell-dependent antibody formation in composite cultures containing T cells or T-cell-substituting B-cell mitogens, B cells, and macrophages, always required the presence of C3-sufficient serum.

Animals↗