Abnormal GC function in Eμ-FOXP1 transgenic mice. (A) Frequencies of unique somatic mutations accumulated in splenic B cells at the V_H186.2 region upon NP immunization of 3 WT and 3 transgenic mice. (B) Distribution of all mutations across the sequenced 273-bp-long V_H186.2 region. (C) Number of mutations detected in each of the 72 sequences analyzed from WT or the 81 sequences analyzed from Eµ-FOXP1 mice. (D) Humoral immune response of WT (n = 6) and Eµ-FOXP1 (n = 7) mice to immunization with NP₍₃₆₎-CGG at different times. Serum anti-NP titers and means are shown. (E) A representative FACS profile of ex vivo class switching from IgM to IgG1 and IgG3. Splenocytes from 2-month-old WT and Eµ-FOXP1 mice were stimulated for 72 hours with LPS or IL-4 plus LPS. The percentage of switched cells is indicated in each plot. (F) Bar graphs represent the normalized switching efficiencies of splenic B cells from WT (n = 5) and transgenic (n = 7) mice that were assayed in 4 different experiments. (G) GLTs expressed by WT (n = 4) and Eµ-FOXP1 (n = 7) splenocytes were assayed by qRT-PCR in 3 independent experiments after stimulation for 50 hours with LPS or IL-4 plus LPS, normalized to Igβ levels and represented relative of those of unstimulated WT cells. All bar graphs represent mean ± SEM. Significance was calculated using 2-tailed unpaired Student t tests. TG, transgenic mice; wks, weeks; WT, wild-type mice.