Cytospin of FACS-purified cells was prepared as described (60 (link)) using Shandon Cytospin 4 (Thermo Scientific). Giemsa-Wright staining was performed using Advia S60 (Siemens) and imaged using Axioimager.Z2 microscope with Axiovision software v4.8 (Carl Zeiss, Germany). Human tonsil paraffin sections were immunostained with the antibodies: anti-AXL (MM0098-2N33, Abcam), CD123 (BR4MS, Leica Biosystems) and CD3 (LN10, Leica Biosystems) using a Ventana Benchmark XT instrument.