CD11b positivity improves discrimination between ALL and normal mature and precursor B cells. Flow cytometric dot plots depict CD19⁺ cells from BM of ALL patients. Leukemic cells are shown as black dots and normal B cells as gray dots. (A) D15 BM sample from a patient with ALL. CD11b in combination with CD10⁺ allows a reliable identification of the leukemia cells, which otherwise have a normal B-cell immunophenotype. (B) Analysis of the day-78 BM sample from a patient with T-cell ALL. The dot plot CD10 versus CD34 displays immunophenotypic pattern characteristic of normal CD19⁺ fraction within regenerating BM. The dot plot CD10 versus CD11b shows a very low CD11b expression in normal CD19⁺ hematogones. (C) The same, as in panel B, dot plot combinations for a patient with PBC-ALL at day 0 (top), day 33 (middle), and day 78 (bottom) of therapy. Note the consistently increased CD11b expression and a concomitant decrease of CD34 and CD10 expression in BM during the therapy. At day 78, the CD10 versus CD11b dot plot but not the CD10 versus CD34 plot clearly discriminates leukemic cells from normal regenerating cells.