STAT3 and neoplasm: Evidence for the involvement of different immunomodulatory mechanisms has been derived from several studies which have shown an increase in tumor infiltrating cells [8], the development of autoantibodies and clinical manifestations of autoimmunity (~30%) [9,10], a decrease in circulating Treg cells [11], modulation of the STAT1/STAT3 balance in tumor cells and host lymphocytes [12], changes in serum cytokine concentrations [13], and normalization of T-cell signaling defects in peripheral blood lymphocytes [14,15].