Presence of L-L Interchain Disulfide Bonds in Reconstituted λG Molecules

When partially reduced and alkylated human γ chains were combined with reduced but not alkylated light chains, the reconstituted reoxidized γG protein possessed 65% of its light chains in the form of L-L disulfide-linked dimers. This suggests that light chains are present in γG molecules in such a position that it is sterically possible for them to come into such close proximity to one another that an L-L disulfide bond can be formed under experimental conditions that do not allow formation of an L-H disulfide bond.

A subclass of human gamma-A-globulins (gamma-A2) which lacks the disulfied bonds linking heavy and light chains

The gammaA2-subgroup of gammaA-globulins, previously delineated by antigenic studies, was found to differ strikingly from other immunoglobulins in the manner in which the polypeptide chains are bound together. The heavy and light chains were not linked to each other by disulfide bonds. Instead the light chains were disulfide linked to one another, and were present in the gammaA2-molecule as disulfide bridged L-L dimers. Antisera specific for gammaA2-proteins indicated the occurrence of two different antigenic types in all normal sera as well as saliva and colostrum. Both of these showed the unique interchain disulfide linkage. Quantitative analyses indicated higher levels of gammaA2-proteins in external secretions.

Catabolism of Human γG Immunoglobulins of Different Heavy Chain Subclasses

The rates of catabolism of human γG immunoglobulins of subclasses γG1, γG2, γG3 and γG4 were studied in heterologous species by determining the rates of elimination from the circulation of pairs of 131I- and 125I-labeled human γG myeloma proteins in mice, rabbits, guinea pigs and squirrel monkeys. In all species studied, γG1, γG2 and γG4 myeloma proteins were on the average catabolized at similar rates, whereas γG3 myeloma proteins were catabolized more rapidly. In contrast, individual myeloma proteins within a given subclass differed significantly in their catabolic rates in mice and monkeys, but except for γG3 myeloma proteins, did not differ in rabbits and guinea pigs. Also, individual myeloma proteins were catabolized differently depending on the species injected, in that certain myeloma proteins had a relatively long half-life in one species but a short half-life in another. These experiments indicate that the homologous species and heterologous species catabolize γG immunoglobulins of different heavy chain subclasses in grossly similar fashion, but that minor structural differences between individual proteins which might modulate the rate of catabolism are only recognized by certain heterologous species and not by others.

Catabolism of human gammaG-immunoglobulins of different heavy chain subclasses. I. Catabolism of gammaG-myeloma proteins in man

The rates of catabolism of human gammaG-immunoglobulins of subclasses gammaG(1), gammaG(2), gammaG(3), and gammaG(4) were studied by determining the rates of elimination from the circulation of pairs of (131)I-and (125)I-labeled gammaG-myeloma proteins in 57 patients suffering from cancer other than multiple myeloma. On the average, gammaG(1)-, gammaG(2)-, and gammaG(4)-myeloma proteins were catabolized at a rate similar to that of normal gammaG-immunoglobulin, whereas gammaG(3)-myeloma proteins were catabolized more rapidly than normal gammaG-immunoglobulin. The average half-lives for the myeloma proteins were 12.3 days for normal gammaG, 11.6 days for gammaG(1), 12.4 days for gammaG(2), 8.2 days for gammaG(3), and 11.3 days for gammaG(4). However, significant differences in catabolic rates were observed when individual myeloma proteins of a single subclass were compared. These individual variations were present within all four heavy chain subclasses. The extent of differences ranged from 10 to 47%. The catabolic rate of normal gammaG was in an intermediate range when compared with myeloma proteins of relatively long and short half-lives. The rate of catabolism of an individual myeloma protein did not correlate with its light chain type, Gm factor, carbohydrate content, or electrophoretic mobility. These findings indicate that the structure(s) related to the catabolism of gammaG-immunoglobulins are complex and differ from one immunoglobulin molecule to another.

Human monoclonal gamma G-cryoglobulins with anti-gamma-globulin activity

Seven human gammaG-myeloma proteins which were also cryoglobulins were studied with respect to their reactivity with gammaG-globulins as well as with regard to their antigenic classification within the gammaG-heavy chain subclasses. Five of the seven cryoglobulins studied were positive in at least two of the three tests used to assay for anti-gamma-globulin activity. One protein was only weakly positive in one test system and another was negative in all test systems. The structures which were recognized by the cryoglobulins were localized to the Fc-fragment. Only primate gammaG-globulins contained these antigenic determinants and in some cases the cryoglobulin appeared to show specificity for one human heavy chain subclass over the others. Antigenic analysis revealed that four of the five cryoglobulins with definite antibody activity belonged to the gammaG3-subclass, the fifth belonged to the gammaG1-subclass. The two cryoglobulins which reacted only weakly or failed to combine with gammaG-globulins were both of the gammaG1-subclass. These findings taken together with the localization of the combining site to the Fab-fragment suggests that many of these cryoglobulins may represent antibodies to gammaG-globulin, and that the cryoprecipitate in these cases represents antigen-antibody complexes of such a nature that they precipitate only in the cold.

A case of tetramer Bence Jones proteinaemia

A case of Bence Jones proteinaemia without concomitant Bence Jones proteinuria is described. The protein consisted of four λ type light chains with a molecular weight of 84,000. A pair of dimers were non-covalently bonded to form the tetramer. The dimers in turn were formed of disulphide linked monomers. The absence of proteinuria is discussed with regard to the renal clearance of a tetramer Bence Jones protein compared to that of a monomer or dimer protein.

Evaluation of Light Chain Antigen Binding by Radioimmunoelectrophoresis

The ability of radioimmunoelectrophoresis to demonstrate specific antigen binding directly by isolated antibody light chains was evaluated using BSA as the antigen. Radioactive arcs and specific I*BSA binding were readily demonstrated by light chain preparations which did not contain detectable amounts of heavy chains when tested by gel diffusion.

The arcs observed, however, could not be interpreted as evidence for I*BSA binding by isolated light chains because: 1) as little as 0.19 µg/ml of isolated antibody heavy chains were sufficient to detect I*BSA binding using radioimmunoelectrophoresis whereas 544 µg/ml of the isolated light chains were required; 2) when hybrid molecules made by mixing normal light chains with small amounts of antibody heavy chains were tested, a radioactive are developed that was qualitatively similar to the arc produced by the antibody light chain preparations; and 3) the amount of antibody heavy chains required to produce radioactive arcs when mixed with light chains was less than the amount of antibody heavy chain that could have been detected in the antibody light chain preparation.

False Positive Radio-Immunoautograph Lines Associated with Immunoglobulins from Normal Sera

Radio-immunoelectrophoresis and radio-immunodiffusion are practical methods to detect antigen binding in immunoglobulins and immunoglobulin sub-units. The lower limit of sensitivity of radio-immunodiffusion was 0.003 µg N anti-BSA/ml. The advantages of these sensitive procedures may be limited at times by the occurrence of positive reactions which are not specific, and experiments are described that account for some of these reactions. Recommendations to prevent some nonspecific reactions and to enhance the proper interpretation of positive results are presented.

Carboxy-terminal amino acids of gamma-A and gamma-M heavy chains

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

Duck Immunoglobulins

Studies of the metabolism of duck 7.8S and 5.7S γ-globulins indicated that the 5.7S protein was present in large quantities in fresh duck serum and that there was no detectable in vivo conversion of the 7.8S protein into the 5.7S protein. It was concluded from this that the 5.7S protein was a de novo synthesized protein. Anti-bovine serum albumin (BSA) was 75 to 85% 5.7S γ-globulin after the 3rd week of immunization and 15 to 25% 7.8S.

Reduction of the 5.7S and 7.8S duck antibodies led to a 75% decrease in the half dissociation time of preformed antigen-antibody complexes whereas rabbit antibody was not affected by this treatment. Reduction also decreased the antigen binding capacity of the 5.7S antibody but had little effect on the 7.8S antibody. Passive hemolysis of BSA-coated sheep erythrocytes indicated that only the 7.8S antibody was able to fix duck complement. Also, the 7.8S antibody and not the 5.7S antibody was capable of eliciting a passive cutaneous anaphylaxis reaction in duck skin.

Duck Immunoglobulins

Investigation of the sera from three species of duck has demonstrated the presence of two major low molecular weight γ-globulins, a 7.8S and a 5.7S protein. The 7.8S protein shows similarities to mammalian γG-globulins when products of reduction and enzymatic cleavage were investigated.

The 5.7S γ-globulin had several interesting characteristics. It lacked certain antigenic determinants of the Fc fragment that were present on the 7.8S protein, yet had no detectable unique antigens to suggest it contained structural components that differed significantly from those found on the 7.8S protein. Gel filtration of the peptide chains indicated that the 5.7S protein had a smaller heavy chain than that of the duck 7.8S γ-globulin or mammalian γG-globulin. Also, reduction in the absence of denaturing agents caused a decrease in S rate from 5.7S to 3.5S. These data suggested that the duck 5.7S immunoglobulin lacked a considerable segment of the Fc fragment of the heavy chain. As a result of this, inter-H chain non-covalent bonds were sufficiently small in number so that reduction of the inter-H chain disulfide bond(s) lead to the formation of half molecules.

Recombination of heavy and light chains of human gamma-a-myeloma proteins: formation of hybrid molecules and configurational specificity

The present studies demonstrate that the conditions necessary for reductive cleavage, isolation, and recombination of L and H polypeptide chains of human gammaA-myeloma globulins parallel those required for similar manipulation of the component chains of gammaG-globulin. Specificity of recombination was shown for chains derived from the same protein. In contrast, no intradass preferential recombination was demonstrable. Hybrid molecules, formed by reassociation of noncovalent bonds, could be synthesized from isolated chains of two immunoglobulin classes resulting in the formation of molecules of the type gammaA-H-gammaG-L and gammaG-H-gammaA-L. Several sera containing both gammaA- and gammaG-"monoclonal" peaks were studied, one of which demonstrated the L chains associated with both peaks to be identical both by electrophoretic mobility in acid-urea gel and antigenic analysis. The possibility is considered that this case represents a naturally occurring analogue of the artificially produced hybrid molecules described in this study. Configurational antigenic specificity of gammaA-myeloma proteins, imposed by the presence of kappa L chains in native and appropriately recombined molecules, provides a further indication of the importance of noncovalent bonds in the establishment of the quaternary structure of these proteins.

Low-molecular-weight proteins related to Bence Jones proteins in multiple myeloma

Urinary proteins distinct from Bence Jones proteins, but sharing antigenic determinants, were found in the urine of a number of patients with multiple myeloma. These components were smaller in size and antigenically deficient compared with Bence Jones proteins. They were best detected with antiserums to the homologous Bence Jones proteins and, in some cases, were related to the variable portion of the Bence Jones protein molecule.