Light Chain Interaction Research Articles

The Interaction of Immunoglobulin Heavy and Light Chains in the Absence of the VH Domain

Recent studies of the micron- and kappa-chains of the first patient (GLI) with micronHCD indicated that the observed defect was the result of the failure of assembly of the intact kappa-chain to the micron-chain, which lacked the VH domain but had the CH1 Cys normally linked to the light chain. To explore the possibility that the VH region is necessary for the formation of the HL disulfide bond, in vitro studies were performed with GLI micron- and kappa-chains and with the CH1 domain and kappa-chain derived from an IgG3 myeloma protein, KUP, which yields separate VH, CH1, and kappa-chains after papain digestion and reduction. The proteins were reduced and allowed to reoxidize, and the combination products were assessed by gel chromatography under dissociating conditions by SDS-PAGE and by immunoprecipitation techniques. The results suggest that, although in vitro covalent and noncovalent combinations are possible between intact light chains and their autologous heavy chains even in the absence of the VH domain, the efficiency is less than that when the intact Fd region is used. Hence, it seems likely that lack of VH alone is not sufficient to explain the failure of assembly observed in muHCD.

Studies on fd fragments of human immunoglobulins. III. Immunogenic properties of gamma chains, myeloma fd gamma, and myeloma fd1 alpha.

Earlier studies on antisera against Fab of pooled human IgG and IgA myeloma proteins disclosed the presence of class-specific Fd antibodies, the demonstration of which required interaction of heavy and light chains. To extend our knowledge about the antigenic structure of the Fd fragment of human immunoglobulins, antisera were prepared in rabbits against gamma chains of pooled IgG and of four IgG1 myeloma proteins, and Fd gamma fragment and a cyanogen bromide-produced CH1 preparation of an IgG1 myeloma protein, and an Fd' alpha fragment of an IgA1 myeloma protein. No antigenic determinants exclusively confined to the CH1 region of intact human IgG could be demonstrated with these antisera. The antigenic structure of CH1 intact immunoglobulins may thus only be defined by light-chain-dependent determinants.

The binding of haptens by the polypeptide chains of rabbit antibody molecules.

1. The binding of haptens by the polypeptide chains derived from two rabbit immunoglobulin G antibodies was examined by gel chromatography and equilibrium dialysis. 2. The gamma chains were examined in a dilute sodium acetate buffer, pH5.4, in which they exist as a monodisperse solution of dimers; aggregation of the protein promoted by some haptens had to be avoided. These chains exhibited variable extents of binding, reflecting the specificities of the parent antibody molecules, usually with only small increments above the binding by gamma chains from normal immunoglobulin G. 3. The light chains existed as an interconverting mixture of monomers and dimers in all buffers of near neutral pH that were examined. They bound small amounts of hapten, again broadly reflecting the specificities of the parent antibody molecules. 4. For both the gamma and light chains the dimeric state appeared necessary for appreciable binding of hapten. Apparently in each case the partners in the dimer interact in a manner analogous to the gamma chain-light chain interaction in the parent antibody molecule, to give a site analogous to the antibody site. This implies that the binding of antigens by isolated chains has a large fortuitous element, providing no reliable indication of their contributions to the original antibody sites.

An Immunochemical Approach to the Interaction of Light and Heavy Chains in Myosin

Myosin from vertebrate skeletal muscles has two large polypeptide chains, each with a mass of about 200,000 daltons, and four smaller subunits in the range of 20,000 daltons (Lowey et al., 1969; Gershman et al., 1969; Gazith et al., 1970; Weeds and Lowey, 1971; Lowey and Risby, 1971). The heavy chains are folded into a rodlike α-helical conformation that extends over a length of about 1400 Å and terminates in two globular regions, each about 100 Å in diameter (Lowey et al., 1969). The light chains are located in the globular portion of the molecule where they are believed to be involved in determining the enzymic activity of myosin (Stracher, 1969; Driezen and Gershman, 1970).

Immunochemical analysis of the cross-reacting idiotypes of mouse myeloma proteins with anti-dextran activity and normal anti-dextran antibody.

The idiotype of the mouse myeloma protein with anti-alpha-1,3 dextran activity, J558, has been characterized by a solid-phase radioimmunoassay. The idiotype of the J558 protein depends on a specific light and heavy chain interaction and is altered in the presence of the hapten, nigerose. Cross-reacting idiotypes were found on another mouse myeloma protein with alpha1,3 dextran specificity, normal anti-dextran antibody, and certain reconstructed myeloma proteins composed of the J558 heavy chain and heterologous light chains.

Genetics of the antibody response to dextran in mice.

The immune response to dextran having the alpha-1,3 linkage may be under the control of antibody structural genes. Mice that respond well to this antigen produce antibody restricted with respect to light chain class (lambda) and to an antigenic determinant resulting from a particular heavy and light chain interaction. The response to dextran is controlled by a locus linked to the-heavy chain locus.

The effect of the interaction of heavy and light chains of IgG on the Gm and Inv antigens.

Studies of isolated polypeptide chains, of reconstituted, and of intact IgG show that the antigens present on the Fab fragment, Gm (3), Gm (4), and Inv (1), depend upon the interaction of heavy and light chains for their full antigenic expression, while the antigens of the Fc portion of the heavy chain, Gm (1), Gm (5), Gm (13), and Gm (14), have the same antigenicity in intact IgG, in isolated heavy chains, and in reconstituted IgG. Hybridization experiments using Bence-Jones protein light chains indicate that different homogeneous populations of light chains differ in their ability to restore Gm (3) and Gm (4) antigenicity and that this ability is independent of light-chain antigenic type.