Requirement of NIK-mediated signaling in stromal cells for the emigration of peritoneal B cells. (A) aly mice were intraperitoneally (i.p.) transferred with WT (top panels) or aly (bottom panels) stromal cells. Two weeks after cell transfer, mice were treated with FTY720 for the analysis of peritoneal B-cell populations. Flow cytometric data are representative of 3 independent experiments and are presented as means plus or minus SEM (n = 3). (B) Expression of ICAM-1 (top panels) and VCAM-1 (bottom panels) on WT (thin lines) and aly (thick lines) stromal cells was determined by flow cytometry (left). Twenty-four hours after treatment of stromal cells with various concentrations of S1P, FTY720, or IFNγ (50 units/mL), expression of ICAM-1 and VCAM-1 was determined by flow cytometry. Relative mean fluorescence intensity (MFI) was expressed as a ratio to MFI of untreated cells. Data are representative of 2 independent experiments, and bars indicate mean values. (C) Expression of chemokines (CCL19, CCL21, and CXCL13) in stromal and spleen cells was examined by RT-PCR. Data are representative of 3 independent experiments.