Fig. 3.

Thymic B cell class switching does not require T_FH. (A) Immunofluorescence of the thymus showing UAE-1 (green), β5T (red), and CD19 (cyan). Medullary regions are outlined by a white dotted line. (B) Volcano plot representation of RNA-Seq data comparing isotype class-switched thymic and PP B cells (gray) with overlaid “GSE12366_GC_VS_MEMORY_BCELL_UP” gene set (pink). (C) Flow cytometry overlays of thymic B cells showing IgM by IgD from WT (black) and respective knockout mice (TCRα^−/−, Aicda^−/−, Cd40l^−/−, Icos^−/−, and CD4^Cre/+ Bcl6^fl/fl). (D) Quantification of activated B cells (CD69⁺), isotype class-switched (IgM⁻IgD⁻) and activated IgM⁺IgD^lo thymic B cells. (E) Quantification of isotype class-switched (IgM⁻IgD⁻) B cells in Peyer’s patch of WT and Cd4^Cre/+ Bcl6^fl/fl mice. Each symbol (D and E) represents an individual mouse; small horizontal lines indicate the group mean ± SEM. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001 and ****P ≤ 0.0001 [(D) Two-way ANOVA with Sidak’s multiple comparisons test, (E) Two-tailed unpaired Student’s t test].