CD33 and acute myeloid leukemia: To study target antigen expression in pediatric AML at single-cell resolution, a representative cohort of primary AML samples (n = 30) at diagnosis (n = 20) and relapse (n = 10), including one matched diagnoses/relapse sample, was analyzed by multicolor flow cytometry for CD45, CD34, and CD3 as well as CD33, CD38, CD123, CD135, CD371, CD276, IL1RAP, mesothelin and MICA/B as potential target antigens.