Blood donors and PBMC isolation
Peripheral blood samples were obtained from healthy donors and patients of the Charité - Universitätsmedizin Berlin, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology. All blood donors gave informed consent and the study was approved by the ethical committee of the Charité - Universitätsmedizin Berlin. PBMC were freshly isolated from 20 mL blood by density gradient centrifugation (Biocoll; Biochrom, Berlin, Germany). Heparinized whole blood was layered on the Biocoll Separation Solution and centrifuged at 1200 g for 25 min at 21 °C. PBMC were collected from the interphase, washed and resuspended in RPMI1640 (Gibco, Life Technologies, Darmstadt, Germany) supplemented with 5% human AB-serum (Sigma-Aldrich, St. Louis, MO, USA).