CAT and neoplasm: To confirm that the increased tumor rejection was due to mROS damage to the mtDNANZB Treg cells, we generated a mouse strain that expresses cre-recombinase conditional mitochondrial targeted catalytic antioxidant catalase (mCAT) from within the Rosa26 locus (Rosa26-LSL-mCAT or mCATfl) (Fig. 4A; SI Appendix, Fig. S5 and Dataset S1).