Anti-infective and anti-tumor agents based on the depletion of immune suppressive effects

Aggressive immunity characterized by the motion of cytotoxic T lymphocytes (CTLs), T helper (Th) 1 cells, and natural killer (NK) cells is the first line of defense against intracellular microorganism invasion and tumor formation. In patients with infectious diseases and tumors, aggressive immunity is often attenuated by immune suppressive effects provided by regulatory T (Treg) cells including CD4(+) CD25(+) forkhead-box (fox) p3(+) T cells, T regulatory (Tr) 1, Th3, and a subpopulation of gammadelta-type of T cell receptor-expressing T (gammadelta T) cells. It has been demonstrated that Treg cells down-regulate aggressive immunity by direct cell interactions and suppressive cytokines (e.g., interleukin (IL)-10, transforming growth factor (TGF)-beta). Today, instead of synthesizing chemical agents with serious side effects, protein agents, catalytic oligonucleotides, and natural medicines involved in the elimination of Treg cell-mediated suppressive responses for the restoration of aggressive immunity are expected to be alternatives as a mild clinical remedy against microorganism invasion and tumors.