IL1RAP is overexpressed in AML and can be used as a target for selective antibody-mediated killing of AML cells. (A) AML patients were subdivided into 3 subgroups based on IL1RAP expression levels in mononuclear cells (MNC): IL1RAP low (IL1RAP-L), IL1RAP intermediate (IL1RAP-I), and IL1RAP high (IL1RAP-H). (B) Geometric mean fluorescence intensity (MFI) of IL1RAP expression within the IL1RAP-L, IL1RAP-I, and IL1RAP-H groups compared with normal BM and PB samples. Mean and standard error of the mean is presented. (C) Geometric MFI of IL1RAP expression within CD34+CD38+ cells from normal BM or AML patients. (D) Geometric MFI of IL1RAP expression within CD34+CD38− cells from normal BM or AML patients. (E) Frequency of dead cells (measured as % 7AAD+ cells after subtracting % 7AAD+ cell in the corresponding isotype control group) in an ADCC assay of normal BM MNC and MNC from AML patients (AML 17, 19-23, 27, and 29). The KU812 cell line with a high IL1RAP expression was used as a positive control. (F) Frequency of dead cells in an ADCC assay of sorted CD34+CD38− and CD34+CD38+ cells from normal BM or AML MNCs. Based on availability of cells, we selected 3 patients from the IL1RAP-I group (AML 7, 9, and 10) and 1 patient from the IL1RAP-L group (AML 2). (G) Engraftment of human AML cells (CD45+) in BM of immunodeficient mice, following in vitro ADCC using mAb 81.2 or an isotype control. Flow cytometry was performed at time of sacrifice 3 weeks posttransplantation.