Polymer formation during the degradation of human light chain and Bence-Jones proteins by an extract of the lysosomal fraction of normal human kidney

Abstract

The catabollism of the light polypeptide chains of human immunoglobulins in the kidney has been studies in vitro using an extract of lysosomal fraction of an homogenate of normal human kidney tissue. Both the light (Lc) chains of humna IgG as well as human Bence-Jones proteins are reapidly degraded to non-TCA precipitable fragments. Both human albumium an dintact IgG are relatively unaffected by the lysosomal enzyme under the same conditions of pH 5·0 and added reducing substance. In the process of such enzymatic breakdown, a polymer, insoluble under physiological conditions if formed and then degraded under further enzyme action. Analysis ofthe process of polymer formation by gel filtration and immunoelectrophoresis indicates the transient association of intact molecules with either the common or variable halves of the chain. The formation of large poorly soluble molecular complexes in the process of catabolism may have implications in studies of the renal lesions associated with multiples myeloma, the renal tubular acidosis associated with hyperglobulinemia, and in the renal lesion of systemic lupus erythematosus.