Expression of the transcription factor GATA-3 is strongly associated with T helper type 2 (T(H)2) differentiation, but genetic evidence for its involvement in this process has been lacking. Here, we generated a conditional GATA-3-deficient mouse line. In vitro deletion of Gata3 diminished both interleukin 4 (IL-4)-dependent and IL-4-independent T(H)2 cell differentiation; without GATA-3, T(H)1 differentiation occurred in the absence of IL-12 and interferon-gamma. Gata3 deletion limited the growth of T(H)2 cells but not T(H)1 cells. Deletion of Gata3 from established T(H)2 cells abolished IL-5 and IL-13 but not IL-4 production. In vivo deletion of Gata3 using OX40-Cre eliminated T(H)2 responses and allowed the development of interferon-gamma-producing cells in mice infected with Nippostrongylus brasiliensis. Thus, GATA-3 serves as a principal switch in determining T(H)1-T(H)2 responses.

Using a mouse model in which tumors show a growth-regression-recurrence pattern, we investigated the mechanisms for down-regulation of cytotoxic T lymphocyte-mediated tumor immunosurveillance. We found that interleukin 4 receptor (IL-4R) knockout and downstream signal transducer and activator of transcription 6 (STAT6) knockout, but not IL-4 knockout, mice resisted tumor recurrence, which implicated IL-13, the only other cytokine that uses the IL-4R-STAT6 pathway. We confirmed this by IL-13 inhibitor (sIL-13R alpha 2-Fc) treatment. Loss of natural killer T cells (NKT cells) in CD1 knockout mice resulted in decreased IL-13 production and resistance to recurrence. Thus, NKT cells and IL-13, possibly produced by NKT cells and signaling through the IL-4R-STAT6 pathway, are necessary for down-regulation of tumor immunosurveillance. IL-13 inhibitors may prove to be a useful tool in cancer immunotherapy.

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