HLA surface expression of primary CML cells. HLA class I (A) and HLA-DR (B) expression was determined by flow cytometry for CD33⁺ and CD13⁺ myeloid cells, as well as for CD117⁺CD34⁺ precursor cells, from the peripheral blood of CML patients (n = 7) at the time of diagnosis. Data points represent individual samples. Horizontal lines indicate mean values ± standard deviation.