As expected, western blot analysis using a carboxy terminus CD20 antibody targeted to circulating PBMCs from patients with B cell hematologic malignancies (CLL and NHL), CBL, B cell lines, or healthy donors revealed immunoreactive bands at 35 kDa corresponding to the full-length CD20 protein, indicating the presence of B lymphocytes in each sample (Fig. 1). Here, MS4A1 is linked to B-cell chronic lymphocytic leukemia.