Figure 1.
B-cell adhesion to MLN HEVs is impaired in CXCL13-deficient mice and is restored by CXCL13 expression. (A) Whole-mount microscopy of MLNs from CXCL13–/– and WT mice. GFP-transgenic B or T cells (green) were injected intravenously into WT and CXCL13–/– mice. Subsequently, Alexa Fluor 594–conjugated MECA89 mAb (red) was injected to label the HEVs in situ. Images were obtained using a Zeiss LSM510 META microscope (Carl Zeiss, Jena, Germany) with a 20×/0.5 numeric aperture (NA) objective. Zeiss Plan NeoFluar. (B) B- and T-cell adhesion to CXCL13–/– and WT MLN HEV segments. HEVs were divided into segments as shown in panel A, and the number of cells bound to each segment was determined. In each experiment, 80 HEV segments/mouse were examined. Data represent the mean ± SD of the number of bound cells per HEV segment in 3 mice. Note that the B-cell adhesion to CXCL13–/– MLN HEVs was about 40% of that seen to WT MLN HEVs (*P < .01). (C) The frequency distribution of adherent B cells per HEV segment. (D) Restoring CXCL13 to the MLN HEVs of CXCL13–/– mice restored B-cell adhesion. After superfusion of MLNs with PBS or CXCL13, GFP-transgenic B cells and Alexa Fluor 647–conjugated MECA89 mAbs (blue) were injected and analyzed as in panel A (right panels). Frozen sections of the MLNs of these mice were stained with an anti-CXCL13 antibody (red; left panels, arrowheads). Images were obtained using a Bio-Rad Radience 2100 microscope (Bio-Rad, Hercules, CA) with a Nikon Plan Fluor 20×/0.45 NA objective.