C. Endogenous co-IP of USP44 and FOXP3 in murine nTregs. nTregs (CD4+CD25high) isolated by FACS were activated by anti-CD3 and anti-CD28 (1 and 4 ug/ml, respectively) overnight in the presence of IL-2 (100 U/ml). The cells were lysed and proteins were immunoprecipitated using either anti-Foxp3 (left panel) or anti-Usp44 (right panel). Proteins pulled down in this experiment were then resolved and identified with the indicated antibodies. 