Analysis of sIgM and μ chain glycoform expression after incubation of CLL samples in vitro. (A) CLL samples were incubated in vitro and the expression of sIgM was analyzed by flow cytometry. The graph shows the fold increase of sIgM (MFI), set at 1.0 at time 0, in the 6 samples. (B) Surface proteins were purified from the CLL samples at time 0 and after 48 hours of incubation in vitro, and μ chains were analyzed by immunoblotting. The immature form (◁) and the mature form (◀) of μ chain are indicated. (C) The graph shows the glycoform ratios at time 0 and after 48 hours of incubation. The difference between ratios at 1 and 48 hours are statistically significant (t test, 2-tailed, paired, 99% CI).