Characterization of subclass-related F(ab)2, Fab-c and Fch fragments obtainined by short papain digestion of human IgG myeloma proteins

When incubated with papain alone, all the IgGI proteins gave a good yield (6- 20%) of fragments (consisting of one Fc joined to one Fab through an unbroken heavy chain). Inclusion of cysteine during the digestion resulted in a mixture of F(ab)₂ and probably F(c)₂ fragments in (a dimer of Fc) in approx. weld. The IgG2 proteins gave mainly F(ab)₂ fragments in up to 12% yield during a short papain digestion in the presence of cysteine. The IgG3 proteins tested gave nearly pure Fch (Fc fragment plus the particular expanded hinge region) when digested without cysteine (yield of 4–25%) . If the papain proteolysis was performed together with cysteine, there was about 5% yield of a mixture of Mw 100,000 fragments The IgG₄ protein used in this study gave approximately 30%. yield of almost pure F(ab)₂ fragments when digested without teine F(ab)₂ fragments were also formed when the IgG4 protein was digested in the presence of cysteine (10% yield).