PRDM1 and acute myeloid leukemia: To this end, we analyzed Bcl6 and Blimp1 transcription factors by flow cytometry in ST2+ Treg cells from leukemic BM, 14 days post-AML challenge, and found that the percentage of Bcl6-expressing Treg cells is decreased in ST2+ Treg cells compared to ST2− Treg cells (Fig. 7K).