CTLA4 and cancer: Splenocytes from tumor free mice treated with anti-PD1 + anti-CTLA4, anti-PD1 + anti-CTLA4 + PRO, and anti-CTLA4 + PRO harbored higher number of tumor reactive T cells with a memory phenotype against MCA205 cancer cells, compared to splenocytes from tumor naïve mice (Fig. 7E, F).