CXCL13 induces B-cell arrest on MAdCAM-1 under flow conditions. (A) B cells were injected at 1 dyne/cm² into capillary tubes coated with MAdCAM-1 with or without various concentrations of CXCL13. The B-cell interactions with MAdCAM-1 were classified into 3 categories as described in “Materials and methods.” (B) B-cell arrest (dotted squares) was seen only in the CXCL13 coimmobilized area. Images were acquired as described in “Flow adhesion assays.” (C) The adhesive interaction of B cells with MAdCAM-1 was abrogated by mAbs to CD49d or MAdCAM-1. (D) The CXCL13-induced B-cell arrest was inhibited by pretreatment of the B cells with PTX. Data represent the mean ± SD for 3 separate experiments. *P < .05 compared with vehicle-treated B cells.