It is well known that CTLA-4 blocking increases Treg proliferation . Accordingly, the proliferation and the amounts of Tregs were enhanced after combinatorial vaccination. Importantly, this increased Treg proliferation was not responsible for the expansion of the antigen-experienced memory CD4+ T cells (manuscript in preparation), as might be predicted by a study using another tumor model where Tregs primarily contributed to the CD137+CD44+CD4+ memory compartment .