AIM2 negatively regulate FOXP3 expression in mouse CD4+ T cells

Absent in melanoma 2 (AIM2) is a cytosolic dsDNA sensor that has been broadly studied for its role in inflammasome assembly and innate immune defense against intracellular pathogens. However, very little is known about the function of AIM2 in adaptive immune cells. The purpose of this study was to investigate whether AIM2 has a cell-intrinsic role in CD4+ T cell differentiation or function. We found that AIM2 is expressed in both human and mouse CD4+ T cells and that its expression is affected by T cell receptor (TCR) activation. AIM2-deficient (Aim2-/-) mouse CD4+ T cells upregulate the expression of regulatory T cell (Treg)-associated genes, both in unstimulated conditions and after TCR activation. Naïve CD4+ T cells from Aim2-/- mice also show a higher tendency to differentiate into FOXP3+ cells in vitro, while their capacity to differentiate into Th1 or Th17 cells remains unaltered. In agreement with these data, in a T cell transfer model of colitis, Aim2-/- naïve T cells induce ameliorated disease and also display a higher ability to differentiate into FOXP3+ cells. Our results suggest that AIM2 negatively regulates FOXP3 expression and Treg cell differentiation. We show that AIM2 function is not confined to innate immune cells but is also important in adaptive CD4+ T cells. Our data identify AIM2 as a regulator of Treg cell differentiation and therefore as a potential intervention target for restoring T cell homeostasis. Sequencing of mRNA libraries from splenic CD4+ T cells isolated from wild type (C57BL6) and AIM2-deficient mice (Aim2-/-). Cells were either left unstimulated or stimulated with anti-CD3/CD28 antibodies.