Dicer-deficiency in antigen-activated B cells leads to severe impairment in GC B-cell formation. (A) Flow cytometric analysis of splenic GC B cells from Dicer1^+/+Aicda^Cre/+ and Dicer1^fl/flAicda^Cre/+ mice 10 days after immunization with NP₃₈-CGG. CD19⁺ splenic B cells were stained for the expression of PNA, GL-7, CD38, and Fas. (B) Confocal immunofluorescence microscopy of spleen cryosections from Dicer1^+/+Aicda^Cre/+ and Dicer1^fl/flAicda^Cre/+ mice 10 days after immunization performed as described in “Histology.” The sections were stained with anti-IgD (red), anti-CD35 (blue), anti–GL-7 (green) antibodies or PNA (green) to visualize B-cell follicles (IgD⁺), FDCs (CD35⁺), and GC B cells (GL-7⁺ or PNA⁺). (C) Flow cytometric analysis of NP-specific IgG1 cells in the spleens of mice 10 days after immunization using the same gating as in Figure 2A. Numbers adjacent to outlined area indicate the percentage of cells in the gate. Data are representative of more than 10 (A,C) or 8 (B) experiments.