BACKGROUND

Experimental autoimmune encephalomyelitis (EAE) is a murine model of multiple sclerosis mediated by CD4+IL-17a producing (Th17) cells.  Mice lacking functional dedicator of cytokinesis 8 (DOCK8) have elevated Th17 cells but do not develop EAE. How DOCK8, a guanine exchange factor expressed by immune cells confers protection to EAE is unknown.

OBJECTIVE

We examined the role of DOCK8 on Th17 cell function ex vivo in both the steady state and in a neuroinflammatory setting. Further, we assessed the migration and functional capacity of Th17 cells in vivo in DOCK8 mutant mice.

METHOD

Dock8-/- mice, lacking functional DOCK8 protein were immunised with a neural peptide to induce EAE. CNS infiltrating lymphocytes were quantitated using flow cytometry. Adoptive cell transfer was used to assess T cell migration. T cells isolated from protected mice were tested for their ability to undergo cell differentiation in vitro using cell culture and flow cytometry. Western blot and qPCR were used to analyse protein and RNA expression by cell subsets of DOCK8 mutant mice.

RESULTS

In vitro T helper cell differentiation confirmed that the elevated Th17 cell population was not based on a T cell intrinsic differentiation bias or altered apoptosis. Th17 cells expressed normal Th17 cell specific CCR6 levels and migrated towards chemokine gradients in transwell assays. Adoptive transfers of Th1 and Th17 cells in EAE mice indicated a Th17 cell specific migration defect in the absence of functional DOCK8.

CONCLUSION

Mice lacking functional DOCK8 are protected from EAE by reduced CNS infiltration of CD4 T cells.  Despite increased resting Th17 cells and normal in vitro differentiation, DOCK8 deficient mice have dysfunctional Th17 cell migration in EAE. DOCK8 thus appears to function by regulating Th17 cell migration into inflamed CNS tissue.