Analysis of μ chains expressed by surface IgM of CLL and normal B cells. (A) Surface proteins were purified from normal B cells and chronic lymphocytic leukemia (CLL) samples, and μ chains were analyzed by immunoblotting. Results are shown from 2 healthy donors (BC1 and BC2) and 10 CLL samples (5 M-CLL, 5 U-CLL), representative of a total of 34 CLL samples. The ratio of expression of the 2 glycoforms of μ chain (mature-immature) is shown for each CLL sample. The immature form (◁) and the mature form (◀) of μ chain are indicated in panels A and B. (B) Purified surface proteins or total cell lysates were treated with EndoH or PNGase or left untreated and analyzed by immunoblotting. Results from 2 healthy donors (BC1 and BC2) representative of a total of 5 independent experiments, and 2 CLL samples representative of a total of 6 independent experiments are shown.