Structure and Evolution of Kappa and Lambda Light Chains

Fifteen years ago when the first structural studies on myeloma globulins and Bence-Jones proteins were begun (Putnam, 1953), none could predict that these clinical curiosities would become today's models for antibody structure, or that the variation in their amino acid sequence would provoke the spate of theories about antibody formation that we are called together here to discuss. There was a rationale in the choice of Bence-Jones proteins for experimental study. Nature, even in disease, never produces a truly abnormal metabolite de novo. Metabolic pathways may be interrupted, diverted, accelerated, or aborted but it takes eons to develop a new pathway, and countless generations for proteins to alter radically in primary structure. It is this structural evolution of kappa and lambda light chains that concerns us today as well as the relationship of light chains to antibody structure and specificity.