Purified B cells were cultured for 3 days and stained with 5 μg/mL propidium iodide (PI; Invitrogen) or TUNEL (Roche, Switzerland) according to the manufacturer’s recommendations. The cells were analyzed on a FACS Calibur (BD). Supernatants were collected from naive and memory B cells grown for 7 days

(0.2×106 cells/500 μL in 48-well plates). Secreted Igs were measured by Human IgA, IgM and IgG ELISA Quantitation Sets from Bethyl Laboratories (TX, USA). Absorbance was measured LY2157299 by a Sunrise Plate Reader (Tecan, Switzerland) set at 450 nm. All labeling reactions were performed by incubating cells with Abs for 30 min at 4°C. When an unconjugated primary Ab was used, the cells were washed twice before incubation with the secondary Ab. The cells were analyzed on a FACS Calibur Flow Cytometer, LSR II or FACS Canto (all from BD). Data were collected using FACS Diva software whereas analysis was performed using FlowJo (Tree Star, OR, USA) or Cytobank software (www.cytobank.org). CD19+CD27− naive and CD19+CD27+ memory B cells were obtained by staining CD19+ selected B cells from peripheral blood with anti-CD19 PECy5 and anti-CD27 PE mAbs and sorting on a FACS DiVa or FACS Aria Flow Cytometer (BD). We did not divide between selleck products switched memory and IgM-memory B cells, but grouped them together as one population. Different subpopulations

from tonsils were obtained by staining the single-cell suspension with anti-CD38 FITC, anti-CD19 PE, anti-IgD PerCPCy5.5, anti-CD5 PECy7 and CD27 allophycocyanin and sorting the following Tacrolimus (FK506) populations: naive B cells (CD19+IgD+CD38−CD27−CD5−), memory B cells (CD19+IgD−CD38−CD27+CD5−), GC B cells (CD19+IgD−CD38+CD27−CD5−) and non-B cells (CD19−). Cells were stimulated for 1 h or as indicated, before they were lysed in Tris lysis buffer as described previously 55. Cell lysates were electrophoresed using 10% SDS-polyacrylamide gels (Pierce, IL, USA) and transferred to PVDF membranes

(Millipore, MA, USA). The membranes were blocked for 60 min with 5% BSA (Sigma-Aldrich) with TBST before they were incubated with primary Abs overnight. After washing in TBST, the membranes were incubated for 60 min with HRP-conjugated anti-rabbit or anti-goat IgG Ab (Dako). Protein bands were visualized by the ECL or ECL-plus detection system (GE Healthcare, NJ, USA). Protein expression was quantified by scanning hyperfilms and using Quantity One Software (Bio-Rad, CA, USA). Cells were fixed in 4% PFA (Electron Microscopy Sciences, PA, USA) in PBS, washed in PBS and permeabilized in 90% methanol in PBS at −20°C. After washing in PBS, cells were incubated in blocking buffer (1 mg/mL human γ-globulin (Sigma) in 0.9% NaCl) at room temperature for 30 min, followed by incubation with primary Abs (diluted in blocking buffer) in a humid chamber at 4°C overnight.