Bence jones proteins and light chains of immunoglobulins—XXVII

Light chains of human immunoglobulins can be cleaved specifically by several types of endopeptidases into fragments corresponding to the amino-terminal, variant (V_L) portion, and to the car☐yl-terminal, constant (C_L) portion. We have investigated the effect of two human polymorphonuclear leucocyte-derived neutral proteases, the elastase-like protease (ELP) and the chymotrypsin-like protease (CLP), on Bence Jones proteins representative of the four structurally and immunochemically-defined groups of human kappa light chains. When κI, κII, κIII and κIV proteins were incubated with ELP or CLP, the result was an extensive proteolysis of the C_L portion of these molecules and the generation of V_L-related fragments. However, the V_L portions of certain κ-chains classified immunologically as a subgroup of κI-chains, κI-1, were also extraordinarily susceptible to proteolysis by these granulocyte-derived neutral proteases. These findings have provided new evidence relating specific structural and antigenic features of human kappa light polypeptide chains.