8 The continuous

wakefulness condition was performed in order to distinguish sleep-dependent and diurnal variations in T-cell responses. Inclusion criteria for volunteers were as follows: mental and physical health (determined from medical history, physical examination and routine laboratory testing); a body mass index between 18 and 26 kg/m2; no sleep disturbances; non-smoker; and not taking medication. Each subject participated in two experimental sessions, each covering 24 hr R788 datasheet and starting at 20:00 hr. Each subject spent an adaptation night in the sleep laboratory, where sleep was determined offline from polysomnographic recordings according to standard criteria.32 All subjects received standardized meals and blood samples were processed immediately. An intravenous forearm catheter (Braun, Melsungen, Germany) was connected to a long thin tube, allowing blood collection from an adjacent room without disturbing the subject’s sleep. Blood samples, taken at five time-points (20:00, 02:00, 07:00, 15:00 and 20:00 hr) into heparin anticoagulant, were used for isolation and functional analyses of CD4+ CD25high nTreg and CD4+ CD25− Tres. Hormone levels were measured periodically every 3 hr. The protocol

was approved by the local ethics committee and all subjects signed informed consent forms. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood applying into CPT® Vacutainer (BD Biosciences, Heidelberg, Germany), according to the Metformin in vitro manufacturer’s instructions. Plasma was collected, inactivated by heating at 56° for 30 min

and then centrifuged at 4500 g. The supernatant was designated Florfenicol as autologous inactivated plasma. T cells were isolated from PBMC and separated into nTreg and Tres populations using the CD4+ CD25+ Regulatory T Cell Isolation Kit® (Miltenyi Biotec, Bergisch-Gladbach, Germany), according to the manufacturer’s instructions, in combination with an autoMacs® Separator (Miltenyi Biotec). We subsequently refer to this isolation protocol as MACS®. For logistical reasons we performed this protocol for the diurnal analysis. Cell purities were examined using flow cytometry. As a control for the results obtained with MACS-isolated Tres and nTreg we also performed an isolation protocol where negatively MACS isolated CD4+ T cells were sorted in CD25− and CD25high T cells by fluorescence-activated cell sorting (FACS), using MoFlo® (DakoCytomation, Hamburg, Germany). We will refer to this isolation protocol as MACS + Sort. The CD4− cells were enriched for monocytes by plastic adherence for 2·5 hr and, after harvesting, were irradiated with 60 Gy using a cobalt source. For proliferation assays, half of the Tres obtained were stained with carboxyfluorescein diacetate (CFSE) and the other half were left unstained for control purposes. For analysis of the suppressive activity of nTreg on Tres, we employed a procedure described previously33 with minor modifications.