Sample collection and total RNA extraction

Whole blood was collected in an EDTA-containing tube within a maximum of 24 hours after hospital admission. The peripheral blood mononuclear cells (PBMC) were immediately separated by gradient centrifugation using Ficoll-Paque Plus (GE Heathcare, cat. no. 17144002). After cell separation, the PBMC were collected, preserved in RNAlater (Qiagen, cat. no. 76106) and stored at -20°C until RNA extraction. PBMC were lysed with 300 μl of RLT buffer and the total RNA was extracted using RNeasy Mini Kit (Qiagen, cat. no. 74106). RNA purity analysis and quantification were performed using the NanoVue spectrophotometer (GE Heathcare Life Sciences, Marlborough, MA). RNA quality was assessed on the Agilent BioAnalyzer 2100 (Agilent, Santa Clara, CA). All samples presenting RIN ≥ 7.0 were stored at -80°C until used in hybridization experiments.