Accumulating evidences show that many tumor associated antigens expressed on the normal cells and not the product of gene mutation and indicate the tumor immunity is a autoimmunity to some extent. CD4~ CD25~ regulatory T cells (CD4~ CD25~ Treg) can suppress the immune response to self and non-self antigen in active way and contribute to the maitainance for self-immune tolerance. So CD4~ CD25~ Treg may suppress the tumor immunity. CD4~ CD25~  Treg provided a new way to study the relationship between the prog...