SOCS1 negatively regulates the production of Foxp3+ CD4+ T cells in the thymus

SOCS1 profoundly influences the development and peripheral homeostasis of CD8(+) T cells but has less impact on CD4(+) T cells. Despite the moderate influence of SOCS1 in the development of the total CD4 T-cell lineage, we show here that SOCS1 deficiency resulted in a 10-fold increase in Foxp3(+) CD4(+) T cells in the thymus. Increased numbers of Foxp3(+) thymocytes occurred in mice with T-cell-specific ablation of SOCS1, suggesting that the effect is T-cell intrinsic. This increase in Foxp3(+) CD4(+) cells in SOCS1-deficient mice also occurred in the absence of IFN-gamma or/and IL-7 signaling. Increase in CD25(+)CD4(+) T cells in the absence of SOCS1 could be partly due to enhanced survival by CD25(+)CD4(+) cells, to a lesser degree CD25(-)CD4(+) T cells, from SOCS1-deficient mice with or without T-cell growth factors. Immunology and Cell Biology (2009) 87, 473-480; doi: 10.1038/icb.2009.23; published online 21 April 2009