Howard M. Grey

The reaction of monomeric and aggregated immunoglobulins with Cl

Abstract The relative capacity of different immunoglobulin classes and subclasses in different states of aggregation to bind the first component of complement (C l ) was studied. Both monomeric γG and 7S γM immunoglobulins were found to be able to bind C l . The binding capacity of γG myeloma proteins was dependent upon the γG subclass, the order of reactivity being γ G3 > γ Gl > γ G2 > γ G4. No differentiation into functional subclasses was possible on the examination of 12 different monomeric γM preparations. The relative C l binding capacity of γM polymers was: 7S γ M = 1, 19S γ M = 15, 27–35S γ M = 64, and > 35S γ M = 116. Comparable amounts of the 7S subunit of γM and γG bound C l to a similar extent, and aggregated γM and γG were also comparable in C l binding, suggesting that the differences in the relative C l binding capacity of these immunoglobulins is dependent upon the degree of polymerization that is present in the native state of these proteins. The Fc fragment of γCl was as efficient as the intact protein in fixing C l , when compared on a molar basis; human F(ab′) 2 and the cyanogen bromide treated Fc fragment were unable to bind C l .

Carboxy-Terminal Amino Acids of γA and γM Heavy Chains

The carboxy-terminal amino acids of α-and �-chains from human immunoglobulins and α-chains from mouse immunoglobulins have been determined by carboxypeptidase digestion and hydrazinolysis. The data suggest the following carboxy-terminal sequences: human �: Ala-Gly-Thr-Cys-TyrCOOH; human α: Thr-Cys-TyrCOOH; murine α: (Ileu, Cys)-TyrCOOH.

Structural characteristics of the Fc′ fragment of human γG-globulin☆

Abstract The Fc′ fragment was isolated from normal human γG-globulin and a γG1(We) myeloma protein. It was shown to be heterogeneous by antigenic analysis, peptide mapping and C-terminal amino acid analysis. It had a molecular weight of 18,000 and contained 1·5 mole of hexose per mole of protein.

Production of Mercaptoethanol Sensitive, Slowly Sedimenting Antibody in the Duck.

Discussion and conclusions The above data indicate the presence of mercaptoethanol sensitive, slowly sedimenting anti-BSA antibody in the duck which by gel filtration and radio-immunoelectrophoresis did not behave like a mammalian 7S γ globulin. The gel filtration experiment suggested that the antibody was somewhat larger in size than the 7S proteins and the radioimmunoelectrophoretic patterns localized the antibody activity to a protein which migrated separately from the 7S γ globulin line. This antibody bears a striking resemblance in some of its characteristics to the β 2A (γ1A) immunoglobulin described in the mammal. Although the evidence is still not complete, data obtained with ragweed skin-sensitizing antibody indicate that β 2A (γ1A) antibodies are a) larger than 7S(8), and b) mercaptoethanol sensitive(9). Mercaptoethanol sensitive, slowly sedimenting antibody has been recently observed in non-mammalian vertebrates such as the chicken(2,3), frog and goldfish(1), and turtle. The finding of this class of antibody in inframammalian species to the apparent exclusion in the cold blooded vertebrates at least of 7S mercaptoethanol resistant antibody suggests that this class of antibody represents a stage in the evolution of the immune response which in the mammal has become largely superceded by mercaptoethanol resistant 7S γ globulin.

BINDING PROPERTIES OF MONOCLONAL γG‐ANTIGLOBULIN FACTORS WITH HUMAN γG*

Cryoglobulins, serum globulins that reversibly precipitate in the cold, are found in patients with multiple myeloma, macroglobulinemia, and a variety of connective tissue disorders.’ Whereas the exact mechanism underlying cryoprecipitation is still unknown, the finding of a high incidence of anti-y-globulin activity among c r y o g l ~ b u l i n s ~ ~ ~ suggests that cryoprecipitates represent antigen-antibody complexes of such a nature that precipitation of the complexes occurs only at low temperature. Recent studies indicated that five out of seven human monoclonal yG-cryoglobulins possessed anti-y-globulin a~ t iv i ty .~ The reactive region of the cryoglobulin molecule was located on the Fab fragment, whereas the yG-globulin determinant(s) recognized by the cryoglobulins was located on the Fc fragment. Specificity of the reaction was demonstrated by the fact that the cryoglobulins combined only with primate yG-globulins and not with other primate immunoglobulins or mammalian yG-globulins. The purpose of the present study was to characterize further the interaction between these monoclonal yG-cryoglobulins and yG-globulin by studying the binding strength of the interaction. For comparative purposes, the relative avidity of human yM-rheumatoid factor and induced rabbit anti-human Fc antibody was also studied.