Dissociated H and L chains of human γG-myeloma proteins were recombined by removal of conditions interrupting non-covalent interactions. In the process of recombination 7S molecules were formed. It was demonstrated that the H chains from individual γG-myeloma proteins recombine with their own L chains but also with L chains derived from other myeloma proteins. In some instances, however, the L chains from other myeloma proteins did not recombine as avidly with the H chains as the autologous L chains.
The specificity of the non-covalent interactions of H and L chains was particularly well brought out by competitive recombination experiments where an individual H chain had a choice of recombining with its own L chain or with the L chain obtained from another myeloma protein. In this manner a spectrum of affinities between individual H chains and several L chains was demonstrated. In the vast majority of recombinations there was a clearcut preference for recombination to take place between the H and L chains derived from the same protein. It is postulated that this specificity is related to differences in the primary structure, which cause differences in configuration of these homogeneous H and L chains and that these configurations then dictate on thermodynamic grounds the pairing of H chains with particular L chains.