DOCK8 enforces immunological tolerance by promoting IL-2 signaling and immune synapse formation in Treg cells

Patients deficient in the guanine nucleotide exchange factor DOCK8 have decreased numbers and impaired in vitro function of T regulatory (Treg) cells and make autoantibodies, but seldom develop autoimmunity. We show that similarly, Dock8-/- mice have decreased numbers and impaired in vitrofunction of Treg cells, but do not develop autoimmunity. In contrast, mice with selective DOCK8 deficiency in Treg cells develop lymphoproliferation, autoantibodies, and gastrointestinal inflammation, despite normal percentage and in vitro function of Treg cells, suggesting that deficient T effector cell function might protect DOCK8 deficient patients from autoimmunity. We demonstrate that DOCK8 associates with STAT5 and is important for IL-2 driven STAT5 phosphorylation in Treg cells. DOCK8 localizes within the lamellar actin ring of the Treg cell immune synapse (IS). Dock8-/- Treg cells have abnormal TCR-driven actin dynamics, decreased adhesiveness, altered gene expression profile, an unstable IS with decreased recruitment of signaling molecules, and impaired transendocytosis of the co-stimulatory molecule CD86. These data suggest that DOCK8 enforces immunological tolerance by promoting IL-2 signaling, TCR-driven actin dynamics, and the IS in Treg cells.   Overall design:  CD4+CD25+CD39+YFP+ and CD4+CD25+CD39+YFP- Treg cells were isolated from the spleen and lymph nodes of Foxp3YFP-Cre/+/Dock8flox/flox mice.  Treg cells were then cultured overnight in complete media alone or in the presence of media + anti-CD3+CD28 beads (1 bead per cell). After 16 hours, cells were harvested and the RNA was isolated. For unstimulated samples, there were 4 independent YFP- samples and 6 independent YFP+ samples.  For bead stimulated samples, there were 3 independent YFP- samples and 2 YFP+ samples.

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Janssen E, Kumari S, Tohme M, Ullas S, Barrera V, Tas JM, Castillo-Rama M, Bronson RT, Usmani SM, Irvine DJ, Mempel TR, Geha RS