Pentameric Molecule Research Articles

Modulation of the assembly of immunoglobulin subunits by J chain.

Because J chain is present in polymeric and not monomeric immunoglobulin molecules and since it is released from polymers when they are reduced to subunits, it has been suggested that J chain plays an important role in the assembly of both IgA and IgM polymers. J chain has been reported (1) to have a high half cystine content (10–12 per mole), and there are, therefore, sufficient cysteine residues to undergo disulfide bond formation with each of the subunits in a pentameric immunoglobulin molecule. Consistent with this thesis are quantitative estimates of the amount of J chain in IgM and IgA suggesting that there is one J chain per mole of polymer regardless of the polymeric size.KeywordsSedimentation CoefficientHalf CystineMayo Medical SchoolChain BandMonomer AlbuminThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Equine anti-hapten antibody—VII. Anti-lactoside antibody induced by a bacterial vaccine

Immunization of a horse with a bacterial vaccine of Streptococcus faecalis, strain N led to the sustained and concomitant production of IgM and 7 S antibody with anti-lactoside specificity. Restriction of heterogeneity was apparent in both mol. wt groups with the IgM population exhibiting three major components when analyzed by isoelectric focusing. Equilibrium dialysis studies of the specific binding of a lactoside hapten, p( p-dimenthylaminophenylazo)-phenyl- β-lactoside (Lac dye), were carried out with three preparations of purified IgM antibody. The intrinsic association constants (K 0) ranged between 1 × 10 5 M −1 and 2 × 10 5 M −1 for bleedings taken from 6 weeks to 14 weeks after the initiation of immunization. The availability of 10 binding sites per IgM molecule was clearly evident with no indication of intramolecular heterogeneity although substantial deviation from homogeneous binding was observed. Conversion of the pentameric IgM molecule to the monomeric form resulted in identical binding behavior. The 7 S antibody fraction gave a maximum value of K 0 of 8 × 10 5 M −1. The binding of lactose by IgM yielded a value of K 0 which was 24-fold smaller than that for the Lac dye. Thus, the nonspecific contribution of the aglycoside, arising presumably from its hydrophobic character, to the free energy of complex formation was - 1·8 kcal/mole of hapten. The temperature dependence of the IgM binding of the Lac dye demonstrated that the enthalpy contribution was primarily responsible for the affinity. From this result it was inferred that the specific binding of lactose involves multiple hydrogen bonds, perhaps as many as 10.

Studies on monoclonal antibodies. I. The specificity and binding properties of a Waldenström macroglobulin with anti- G activity.

Abstract A mixed γM-γG cryoglobulin was identified in the serum of a patient with classical Waldenstrom's macroglobulinemia and hyperviscosity syndrome. The isolated macroglobulin (γM Sie ) contained only kappa-type light chains and an iodinated preparation was quantitatively precipitable by human γG at pH 7.4 in the cold. γM Sie displayed a clearly defined specificity since it reacted with the Fc portion of human γG and rabbit γG but not with other human immunoglobulins nor with bovine, porcine, sheep, chicken, or goat γG. The combining activity was located in the Fab μSie fragments. Direct binding studies performed in the analytic ultracentrifuge demonstrated that essentially all 10 Fab/mole γM Sie were active despite the fact that only 5 were available in the intact pentameric γM molecule. The mean association constant for the interaction between Fab μSie and a γGl, k human myeloma protein equalled 5.5 × 10 4 M −1 . A marked disparity in reactivity was observed in precipitin assays with 125 I-γM Sie and myeloma proteins from the various human γG subclasses or rabbit γG which could not be explained by differences in primary binding affinity. These findings support the hypothesis that γM Sie is a monoclonal antibody to human γG which closely resembles the polyclonal anti-γ-globulin factors that arise during the course of a wide variety of human disorders of diverse etiology. They also suggest that a meaningful relationship exists between paraprotein production and an immune response in pathogenesis of certain plasma cell dyscrasias.

Studies on human secretory immunoglobulin A—III. J chain

J chain has been detected both immunochemically and by disc electrophoresis in human colostral and salivary IgA, in five polymeric myeloma IgA, and in five macroglobulinemic IgM preparations. Serum 7S IgA, IgG, and myeloma IgD are devoid of J chain. Urinary protein from two patients with IgA myeloma of polymeric type had high levels of Bence-Jones protein but no evidence of J chain. For J chain preparation by ion-exchange chromatography, sulfitolysis was preferable to reduction and alkylation because of a better separation of J chain from other subunits. The proportion of one J chain per 11S secretory IgA and per pentameric IgM molecules was determined. It is argued that J chain is not derived from α chain.

Puerperal Fever Treated by Antistreptococcus Serum

Low molecular weight (LMW) IgM is the monomeric subunit of pentameric IgM. It was not found in the sera of 20 healthy subjects but was detected in all six patients with mixed cryoglobulinaemia with a mean value of 1.4 g/l, representing 34% of the total IgM. In three of four patients studied LMW IgM was monoclonal and of the same light chain type (kappa) as the pentameric monoclonal IgM rheumatoid factor (RF) observed in the cryoprecipitate. LMW IgM was proportionately under-represented, however, in the cryoprecipitate compared with the corresponding serum, possibly because of the lower valency of the LMW molecule. Immunoblot analysis of sera showed the presence of other oligomers of IgM in addition to monomeric IgM, suggesting that a disorder of IgM assembly was responsible for its occurrence, and this was supported by the secretion of large proportions of LMW IgM in vitro by peripheral blood mononuclear cells (PBMC) from one patient with this disorder but not from healthy controls. In conclusion, the occurrence of large quantities of monoclonal LMW IgM in mixed cryoglobulinaemia was observed, and it is suggested that this is unlikely to have a direct pathogenic significance. It is postulated that its presence reflects a disturbance of assembly of the monomeric IgM subunits that occurs during the polymerization of the pentameric molecule.