The recombination of dimers of immunoglobulin peptide chains

Abstract

1. Both the γ and light peptide chains of human pooled and myeloma immunoglobulin G can be prepared as non-aggregating dimers at pH5.4 in 4mm-sodium acetate buffer. The dimeric state is maintained by non-covalent bonds, since the formation of interchain disulphide bonds was prevented by alkylation of the thiol groups. In the case of the light chains there is some evidence that the dimers are in equilibrium with a small amount of monomer. 2. When such dimers of the γ and light chains are mixed at pH5.4 in 4mm-sodium acetate buffer they combine rapidly, yielding a product that resembles the original immunoglobulin G in its physicochemical and antigenic properties. However, the original optical rotatory dispersion spectrum was regained only with the homogeneous myeloma protein. The recombined pooled immunoglobulin G had a spectrum slightly different from the original, suggesting that at least some of the recombinant molecules had not regained native conformations. 3. Dimers of γ chains stabilized by interchain disulphide bonds were able to recombine with light chains. However, light chains stabilized in the dimeric state by interchain disulphide bonds would not combine with γ chains. 4. The chains of rabbit immunoglobulin G behave similarly to the human chains in this system, apart from the alkylated light chains showing clearer evidence of monomeric components.