BCR and B-cell chronic lymphocytic leukemia: Using flow cytometry, we measured the levels of the 2 BCR isotypes, defined by mean fluorescence intensity (MFI), on 65 randomly chosen CLL patients of the M-CLL (n = 44) and U-CLL (n = 21) types (Supplemental Table 1; supplemental material available online with this article; https://doi.org/10.1172/JCI149308DS1).