DTx-mediated selective FDC ablation disrupts B cell follicle architecture despite retention of CXCL13. Unimmunized CD21-DTR chimeras were control (Ctrl) or DTx treated 2 d before analysis of spleen (spl) and pLN sections. (A) Immunofluorescence analysis for BP3⁺ stromal cells, CD35⁺ FDCs, and IgD⁺ follicular B cells. (B) In situ hybridization for Cxcl13 mRNA with serial sections stained for B220 and CD35 or for Cxcl13 and CD35. (C) Quantitative RT-PCR analysis for Cxcl13, Cr1 (CD35), Mfge8, and Tnsf13B (BAFF) mRNA in pLNs, spleen, and mLNs, normalized to Hprt mRNA. Data are representative of four experiments (mean ± SEM). Statistical analysis was performed with the two-tailed unpaired Student’s t test. *, P < 0.05; n.s., not significant. (D) Immunohistochemical analysis for CXCL13 and CD3 or B220 in serial sections of spleen and pLNs. Data in A, B, and D are representative of at least three experiments (at least two mice of each type per experiment). Bars: (A [left] and B [left and middle]) 200 µm; (A and D, right) 100 µm; (B [right] and D [left]) 50 µm.