BCL6 and graft versus host disease: GVHD caused ~65% reduction in the percentage of Tfh and GC B cells in B-BCL6+/+–cGVHD recipients as compared to B-BCL6+/+–no-GVHD recipients, although the percentages of these cells were still significantly higher than in B-BCL6−/−–cGVHD or B-BCL6−/−–no-GVHD recipients (Fig. 2f, g).