CD4 and glioma: Treatment of C57BL/6 mice with a single dose of the anti-CD25 mAb clone PC61 prior to orthotopic glioma challenge significantly lowers the number of brain-infiltrating CD4+CD25hiFoxp3+ Treg as compared to IgG control animals when assessed 14 days after tumor challenge (11,2 ± 1,92 × 103  versus 19,6 ± 5,12 × 103, P < 0.05).