CD44 and neoplasm: To understand why the Treg alteration in Prdm1fl/flFoxp3YFP-Cre mice was selectively induced in the tumor but not in the periphery, we performed RNA-seq analysis of splenic and TIL CD44+ Treg cells from WT compared to Prdm1fl/flFoxp3YFP-Cre mice in our B16-OVA/NP-OVA model (Fig. 6a and Additional file 3c).