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Biomedical subjects

J Koyama

Publications and source records attributed to J Koyama.

At least 163 records · Page 9Linked to original sources
PubMed1976

Isolation of two forms of activated C1s, a subcomponent of the first component of rabbit complement.

Two forms of activated C1s, a subcomponent of the first component of complement, were present in preparations of C1 specifically purified from rabbit serum by affinity chromatography on IgG-Sepharose 6B and were separated by DEAE-cellulose chromatography in the presence of EDTA. These two activated C1s, designated C1s(I) and C1s(II), were indistinguishable with regard to hemolytic activity as well as C1s esterase activity, though they had different molecular weights. C1s(I) had a molecular weight of 106,000, consisting of H and L chains connected by disulfide bonds; the molecular weights of the chains were 70,000 and 36,000, respectively. On the other hand, C1s(II), with a molecular weight of 72,000, consisted of two chains each with a molecular weight of about 37,000, which were also connected by disulfide bonds. These results suggest that, in the case of rabbit C1s, the primary product of activation with C1r, C1s(I), may be susceptible to further cleavage of its H chain without any loss of C1s activity, resulting in the formation of C1s(II), though the active principle responsible for this conversion remains to be elucidated.

Animals↗
PubMed1976

In vitro uptake and digestion of immune complexes containing guinea-pig IgG1 and IgG2 antibodies by macrophages.

The uptake and digestion of immune complexes by peritoneal macrophages from oil-stimulated guinea-pigs were studied using 125I-labelled guinea-pig IgG1 and IgG2 antibodies to hen ovalbumin. When the IgG1 or IgG2 antibody was incubated with homologous antigen at antigen-antibody ratios ranging from 0-01 to 10, the complexes produced were preferentially taken up by macrophages in the absence of complement and digestion by intracellular enzymes. The uptake and digestion of complexes reached a maximum at an antigen-antibody ratio of 0-1-0-5. In this respect, the IgG1 antibody was indistinguishable from the IgG2 antibody having a cytophilic activity. These observations suggest that some conformational changes in both the IgG1 and IgG2 antibodies or specific molecular arrangement in the lattice work of both the complexes may increase the strength of binding of complexes to macrophages, independently of the difference in biological activities between these two antibodies.

Animals↗
PubMed1976

Non-precipitating guinea-pig antibodies as products of limited recognition of antigenic sites on the ovalbumin molecule.

The non-precipitating guinea-pig IgG1 and IgG2 antibodies, produced by administration of an excessive dose of hen ovalbumin (OA), were capable of forming only certain soluble complexes having molar ratios of antibody to antigen lower than 1-5:1, which were lower than the minimum ratio of 2-5:1 shown by anti-OA antibodies precipitable with OA. This unusual property of the non-precipitating antibodies was caused by a limited number of antibody molecules capable of binding to one OA molecule simultaneously, since the maximum number of their Fab' fragments binding to one OA molecule was only three and markedly less than the number (7-8) of Fab' fragments of the precipitating IgG1 and IgG2 anti-OA antibodies binding to one OA molecule. These results demonstrate that the non-precipitating IgG1 and IgG2 anti-OA antibodies are those reacting with some particular antigenic sites on OA, a number of the antigenic sites too few to permit insoluble lattice formation.

Animals↗
PubMed1975

Intradermal catabolism of rabbit IgG and its fragments.

Disappearance of rabbit EgG and its Fc fragment from the injected sites in skin and also the relationship to reverse passive cutaneous anaphylaxis (RPCA) were studied using guinea pigs. Rabbit IgG and its Fc fragment, trace labelled with -125-I, disappeared from the injected sites with half-lives of 12--14 and 6--7 hr, respectively. The shorter half-life of the Fc fragment explained why its activity to provoke RPCA disappeared more rapidly than that of intact IgG as the sensitization period was prolonged. The ability to provoke RPCA did not seem to influence the persistence of Fc fragment in the sites, since F(ab')2 as well as Fab fragments had the same half-life as Fc fragment.

Animals↗
PubMed1975

Preferential production of IgG2 anti-hapten antibody by immunization with hapten-conjugated Escherichia coli.

It is well-known that immunization of guinea pigs with hapten-protein conjugates induces concomitant production of IgG1 and IgG2 anti-hapten antibodies. However, the synthesis of antibody to 2, 4-dinitrophenyl groups (DNP) was found to be restricted to one of the IgG antibodies (IgG2 antibody) when guinea pigs were immunized through repeated intraperitoneal injections of 0.1 mg of 2, 4-dinitrophenylated Escherichia coli (DNP-E coli). This selective induction of IgG2 anti-DNP antibody formation occurred both in the presence and absence of Freund's adjuvants, whereas a trace of IgG1 anti-DNP antibody was produced concomitantly on increasing the immunizing dose of DNP-E. coli (3.0 mg) in Freund's complete adjuvant (FAC).

Animals↗
PubMed1975

Acceleration of intradermal catabolism of guinea pig IgG1 and IgG2 antibodies by challenge with antigen.

The intradermal catabolism of antibodies injected in guinea pigs to provoke skin reactions was studied using 125I-labeled guinea pig IgG1 and IgG2 anti-ovalbumin antibodies. Disappearance of both the IgG1 and IgG2 antibodies from injected sites was accelerated by intravenous injection of the antigen. The antigen-antibody complexes produced in vitro were also catabolized more rapidly than free antibodies, when estimated using 125I-labeled antibodies. On the other hand, the catabolism of normal IgG2 was not influenced by local anaphylactic reaction elicited by IgG1 antiovalbumin antibody coexisting at the sites. Therefore, the enhanced catabolism of antibodies on challenge was not caused by increased vascular permeability due to anaphylactic reactions, but by more rapid elimination of immune complexes formed at the sites. The Fc parts of IgG1 and IgG2 antibodies played an essential role in the enhancement of catabolism since the catabolism of the F(ab')2 fragments was not accelerated by complex formation with ovalbumin, but rather reduced.

Animals↗