Quantitative flow cytometry for the differential diagnosis of leukemic B-cell chronic lymphoproliferative disorders

We have investigated whether the quantitative flow cytometry is an useful tool to better characterize B-cell chronic lymphoproliferative disorders (CLDs). Peripheral blood samples from 104 patients with leukemic B-cell disorders and 20 healthy donors were analyzed. Directly phycoerythrin-conjugated CD19, CD20, CD22, CD23, CD79b, and CD5 monoclonal antibodies (MoAbs) and QuantiBRITE pre-calibrated beads were used to calculate the number of antigen molecules per cell, expressed as antibody binding capacity (ABC). As compared to normal controls, in chronic lymphocytic leukemias (CLL) all MoAbs tested, with the exception of CD23 and CD5, showed lower ABC levels. In prolymphocytic leukemias (PL), CD5 and CD23 antigens were constantly absent while lower CD19 and CD22 ABC levels were observed. Hairy cell leukemias (HCL) displayed very high levels of CD20 and CD22. Of interest, splenic lymphomas with villous lymphocytes (SLVL) could be discriminated from HCL for higher CD79b and lower CD19 ABC values. Finally, higher CD20 levels were detected in follicular lymphomas (FL), whereas higher CD79b and CD5 levels characterized mantle cell lymphomas (MCL). Seven out of 61 CLL cases were defined as morphologically atypical. When compared with typical forms, lower levels of CD19 and CD23 and higher CD20 and CD22 ABC values were detected. However, we failed to demonstrate quantitative differences between atypical CLL and MCL. Our results suggest that quantitative flow cytometry may be a useful additional tool to better identify some types of B-cell CLDs.