Synthesis of abnormal heavy chains in Bence-Jones plasma cell leukemia with intracellular IgG.

In a patient with plasma cell leukemia and a kappa type Bence Jones protein in serum and urine, the immunofluorescence study of blood plasma cells showed intracellular gamma and kappa chain determinants. Biosynthesis experiments showed the production of abnormally short heavy chains (45,000 daltons) that assembled with normal sized light chains with a partial block. These abnormal heavy chains were secreted at a slow rate and were degraded after secretion.