Colonization of germ-free mice. Germ-free control and zDCΔMHCII mice were colonized with a mixture of six different intestinal bacteria. Flow cytometric analysis of TFH cells (CD3⁺CD4⁺CD62L⁻CD44⁺PD-1⁺CXCR5⁺) and GC B cells (CD19⁺B220⁺CD38⁻CD95⁺) isolated from mLNs (A) and PPs (B) of control and zDCΔMHCII mice 61 d after colonization. Graphs depict percentage of TFH cells among CD4⁺ T cells and percentage of GC B cells among all B cells in mLNs (A) and PPs (B). Each data point represents one individual mouse (n = 3–5). (C and D) Graphs depict amount of total IgA in feces (C) and serum (D) 61 d after colonization. Each data point represents one individual mouse (n = 3–5). (E) Bacteria were isolated from the feces of control and zDCΔMHCII mice and stained with anti–mouse-IgA. Graph depicts normalized MFI of IgA coated bacteria. Each data point represents one individual mouse (n = 3–5). *, P < 0.05.