Pirfendone reduces the GC reaction in cGVHD mice. Spleens were harvested on day 56 post-transplantation. Splenocytes were stained with fluorochrome-labeled antibodies against CD4, CD19, FAS, GL4, CXCR5, and PD1. Fixed spleen sections were stained with GC B-cell marker rhodamine-peanut agglutinin and 4′,6-diamidino-2-phenylindole. (A-D) Representative flow cytometry plots of GC B cells (FAS⁺GL7⁺) (A) and Tfh cells (PD1^hiCXCR5⁺) (C) in splenocytes. Cells were gated on live CD19 cells and CD4 cells, respectively. Quantification of GC B cell and Tfh cell frequency were showed in (B) and (D). Results were pooled from 2 independent experiments with 5 to 8 mice per group. (E) Representative GC immunofluorescence staining images of the spleens. (F) Size of GCs in the spleen. Five to 6 GCs from each mouse were photographed and size was measured. Five to 6 mice from each group were analyzed. Data are representative of 2 independent experiments with similar results. (G) Frequency of GC in the spleen. The number of GCs in each spleen was divided by the size of the spleen section. Five to 6 mice from each group were analyzed. Data are representative of 2 independent experiments with similar results. *P ≤ .05, **P < .01, ***P < .001; data are shown as the mean ± SEM.