IFN-γ-induced CXCR3 expression on AFCs and GC B cells is T-bet–dependent. Chimeras were prepared by transfer of OTII or both OTI and OTII cells. Seven days after immunization with alumOVA, suspensions of cells from the 2 popliteal LNs for each mouse were prepared. (A-B) The level of T-bet mRNA expression was assessed by real-time RT-PCR in (A) CD138⁺B220^int AFCs and (B) B220⁺GL7⁺Fas⁺ GC B cells. ND indicates not determined, as there were almost no CXCR3⁺ GC B cells. Data are derived from 2 independent experiments with a total of 4 mice per group. (C-E) Further chimeras were constructed by transfer of OTII or both OTI and OTII cells into congenic WT mice or T-bet-deficient mice. Seven days after immunization. (C) Geometric mean ± SD of CD138⁺B220^int AFCs and B220⁺GL7⁺Fas⁺ GC B cells per LN were calculated, and the expression of CXCR3 by (D) CD138⁺B220^int AFCs and (E) B220⁺GL7⁺Fas⁺ GC B cells was assessed by flow cytometry. (F) Numbers on dot plots indicate the percentage of AFC or GC B cells expressing CXCR4 ± SD in T-bet^−/− chimeras that had received OTII + OTI cells. Data are derived from 2 independent experiments with a total of 8 mice per group. The significance of differences is assessed by 2-tailed Mann-Whitney nonparametric statistics; only significant differences are indicated.