Thirty thousands of sorted CD19+ CD25+ or CD19+ CD25− B cells were resuspended in KRG buffer (Krebs-Ringer phosphate buffer) OSI-906 order with Ca2+, containing 0,1% BSA (Sigma-Aldrich) in a final volume of 30 μl and were placed on the upper well in duplicates. Cells were migrated towards different concentration of CXCL13 (50, 100 and 500 ng/ml), KRG buffer containing 0.1% BSA as a negative control added to the lower wells in a final volume of 30 μl. To determine if the migration was random

(chemokinesis) or directed (chemotaxis), 500 ng/ml of CXCL13 was added to both the upper and lower chamber followed by addition of cells to the upper chamber. Cells were incubated in a humidified atmosphere containing 5% CO2 at 37° for 12 h, thereafter the upper cell suspensions was removed, and the plates with the net were centrifuged at 350 g at 4° for 10 min. The net was discarded followed by an addition of 2 μl trypan blue together with 28 μl formaldehyde (4%). Migrated GSI-IX mw cells were manually enumerated using a microscope. Expression of homing receptors.  For flow cytometry analyses, 106 spleen cells were placed in 96-well plates and pelleted (3 min, 300 g, 4 °C). To avoid unspecific binding via Fc-receptor interactions, cells were incubated with Fc-block (2.4G2; BD Bioscience) for 8 min at room temperature. All antibodies were diluted in FACS-buffer (PBS containing, 1% FCS, 0.1% sodium azide and 0.5 mm EDTA). The antibodies used were directly conjugated with phycoerythrin

(PE), Pacific blue (PB) and peridinin chlorophyll protein (PerCp). Antibodies used were anti-CD25 (PC61), anti-α4β7 (DATK32), anti-CD62L (MEL-14), anti-CXCR5 (2G8) Interleukin-3 receptor purchased from BD Bioscience and anti-CD19 (1D3), anti-CXCR4 (2B11) purchased from eBioscience, (San Diego, CA, USA). Cells were stained as previously described, and gating of cells was performed using fluorochrome minus one settings

[13]. All data in the study are presented as levels above the background. Proliferation assay.  Triplicates of sorted CD19+ CD25+ or CD19+ CD25− B cells at a concentration of 2.5 × 105/ml were plated in a volume of 100 μl in round-bottomed 96-well plates and stimulated with either 3 μm CpG-PS, 5 μg/ml E-coli LPS or 0.5 μg/ml of Pam3Cys in a humidified atmosphere containing 5% CO2 at 37° for 48 h and pulsed with 1 μCi 3H-thymidine (Amersham Pharmacia Biotech) for additional 8 h. The cells were harvested onto glass fibre filters (Walluc Oy) and dried, where after incorporated 3H-thymidine was measured using a β-scintillation counter. Statistics.  All statistical analyses have been performed using the Prism software (GraphPad software version 4.0b; La Jolla, CA, USA), and Wilcoxon matched paired test was used when comparing CD25+ to CD25− B-cell subpopulations and Kurskal–Wallis test followed by Dunn’s test for multiple comparisons when comparing more than two cell populations. P < 0.05 was considered as significant. B cells were sorted in to two highly purified populations (>98.