Figure 1.

CD133 marks an aberrant PMF stem cell population that gives rise to pluripotent myeloid progenitors. (A) Detection of CD133 and CD34 HSPC in PBMC from PMF patients (n=36). The incidence of HSPC (defined by CD133 and/or CD34 expression and their light scatter properties) within PBMC (excluding granulocytes and erythrocytes) was determined. Samples with <1% of PBMC were deemed not significant, whereas the remaining samples were divided into three groups based on the distribution of CD133⁺CD34^± and CD133⁻CD34⁺ populations. Pie charts show the distribution of the three fractions and the total incidence of HSPC for each patient. As a control, normal BM cells were depleted for lineage-specific markers and examined for CD133/CD34 expression; the percentage is based on total BM cell numbers. The high proportion of double-positive cells is consistent with earlier studies.¹⁹ (B) Characterization of CD133⁺ cells from patients’ PB or normal BM. Patients’ PBMC were enriched for CD133⁺ cells to >95% using MACS microbeads. FACS analysis of the isolated fraction demonstrated co-expression of CD45 and CD117 (cKIT), characteristic of early stem cells. Alternatively, patients’ PBMC were depleted for cells expressing lineage specific antigens, and then analyzed for CD133 and CD34 expression. Normal BM cells were depleted for lineage-specific antigens by MACS and then analyzed for CD133 and CD34 antigens. Results from one of five independent samples are shown.