Myelomonocytic antigens are rarely expressed on B-lymphocytic leukemia cells

In the light of recent observations reporting that B-lymphocytic leukemia (B-CLL) cells may express a variety of myelomonocytic antigens, 28 patients with B-CLL and B-leukemic lymphocytic lymphoma were studied for the presence of these antigens using monoclonal antibodies to detect CD13, CD33, CD15 and CD14. Analysis of immunofluorescence (IF) was carried out by two procedures; one which employed the standard conventional method of gating used in our laboratory for flow cytometry, while the other procedure increased the sensitivity of the analysis, by moving the marker for IF to the left, so as to widen the gate to include more cells with low IF. Using the conventional methodology, the mean proportion of cells considered positive was less than 3% for any of the 4 markers studied. In only a few patients were 5% or more of the B-CLL cells positive for some of the markers studied (3 patients with 6.2-11.3% CD13+; 2 with 6.0-9.6% CD14+, and one with 11.8% CD15+ cells). No case had more than 2.5% + CD33+ cells. The second procedure with a wider gate to enhance sensitivity for less positive cells, increased the number of positive cells for any of the markers in only 4 patients. These results are contradictory to others reported recently, and some of the possible causes for this discrepancy are discussed. It is suggested that more useful data may be obtained if the level of staining intensity and patterns of positive staining are documented in the future.