Analysis of AML blasts and NKs within PBMCs from the different donor samples. (A) Blast content among PBMCs from the patient at diagnosis and in remission (left and central panels) or from the healthy twin (right) is shown. PBMCs were stained with a FITC-labeled CD45 mAb and analyzed against side scatter (SSC) by flow cytometry. CD45dim x SSCLOW cells have been defined as AML blasts . Dashed line: P1 gate (blasts). Numbers in the corners of quadrants: fraction of total cells falling into this quadrant. (B) Analysis of NK cell content. PBMCs form the same sources as in A were stained with FITC-labeled CD16 and PE-labeled CD56 mAbs. NKs were defined as CD16posCD56pos cells (upper right quadrant). The population in the upper left corner in the left panel is the unusual population of CD56brightCD16neg cells, previously reported in AML samples  as an NK subset that exclusively produces cytokines.