Fig. 4.

Loss of GC B cells reduces the number of Tfh cells, but not memory T cells, in the response to NP-CG. (A) Splenocytes were recovered from Bcl6^+/+ (+/+) and Bcl6^f/f (f/f) mice heterozygous for mb1-cre at day 7 post-immunization with NP-CG in alum, followed by FACS analysis. Dot plots show levels of CXCR5 and PD1 expression by CD4⁺ T cells from the Bcl6^+/+ (+/+, bottom left panel) and Bcl6^f/f (f/f, bottom right panel) mice. Naive mice are also shown as controls (top panels). Percentages of CXCR5^hiPD1^hi cells are indicated. The middle and right panels show the number of Tfh cells and NP-specific/IgG1⁺ GC B cells, respectively, at day 7 after immunization. Naive mice were used as a control for Tfh cells. Circles represent the number of cells in individual mice. Representative results of two independent experiments with three to four mice per group are shown. (B) CD4 T cells from CG-primed Bcl6^+/+/mb1-cre^+/− (+/+) and Bcl6^f/f/mb1-cre^+/− (f/f) and naive B cells with (+) or without (−) NP-specific IgG1 memory B cells (1×10³) were transferred into Rag-1^−/− mice, followed by immunization with soluble NP-CG. The number of total (left panel) and high-affinity (right panel) anti-NP/IgG1⁺ ASCs in the spleen was determined as in Fig.2B. Data are representative of two independent experiments.