Fceri pe

Bones and spleens were crushed, cells resuspended and filtered to obtain a single-cell suspension that was analyzed by flow cytometry on a FACSCanto (BD Biosciences). Cells were stained with the following antibodies: CD45-APC, CD10-BV605, CD15-BV605 and glycophorin A-PE (from BD Biosciences) and CD33-BV421, CD19-PerCPCy5.5, CD34-APCCy7, CD68-PE, CD14-BV605, CD117-PECy7, IgM-PE, CD3-PECy7, FceRI-PE and CD25-BV421 (from BioLegend, San Diego, CA, USA). Control cells were stained with matching isotype controls. Sorting of cells was performed on a FACSAria (BD Biosciences).
For intracellular staining of phosphorylated STAT5 (signal transducer and activator of transcription 5), sorted pre-B cells were fixed in 1.6% paraformaldehyde for 10 min at room temperature. Cells were stored in 90% ethanol in −80 °C until analysis. Cells were washed two times in ice cold phosphate-buffered saline before resuspension in phosphate-buffered saline with 2% fetal calf serum. Cells were kept on ice and stained with antibodies against phosphorylated STAT5 (STAT5P-Alexa Flour 647 from BD) or matching isotype controls. Levels of phosphorylated STAT5 are presented as median fluorescence intensity, normalized to the median fluorescence intensity of isotype-stained cells.