Degradation of Immunoglobulin G by Lysosomal Acid Proteases

Enzyme preparations from bovine spleen, human spleen, and lysosomal fractions of human synovial membrane tissue have been shown to degrade human IgG at pH 3.5. The major proteolytic activity is due to cathepsin D. The products of digestion have been shown to consist of fragments of IgG ranging from a slightly altered IgG with a molecular weight of approximately 135,000 to extensively degraded Fc and partially degraded Fab fragments.