CD5-CK2 Binding/Activation-Deficient Mice Are Resistant to Experimental Autoimmune Encephalomyelitis: Protection Is Associated with Diminished Populations of IL-17-Expressing T Cells in the Central Nervous System

Regulating the differentiation and persistence of encephalitogenic T cells is critical for the development of experimental autoimmune encephalomyelitis (EAE). We reported recently that CD5 has an engagement-dependent prosurvival activity in T cells that played a direct role in the induction and progression EAE. We predicted that CD5 regulates T cell apoptosis/survival through the activation of CK2, a prosurvival serine/threonine kinase that associates with the receptor. To test this hypothesis, we generated mice expressing CD5 with the inability to bind and activate CK2 and assessed their susceptibility to EAE. We found mice deficient in CD5-CK2 signaling pathway were mostly resistant to the development of EAE. Resistance to EAE was associated with a dramatic decrease in a population of effector infiltrating Th cells that coexpress IFN-gamma and IL-17 and, to a lesser extent, cells that express IFN-gamma or IL-17 in draining lymph nodes and spinal cords. We further show that T cells deficient in CD5-CK2 signaling hyperproliferate following primary stimulation; however, following restimulation, they rapidly develop nonresponsiveness and exhibit elevated activation-induced cell death. Our results provide a direct role for CD5-CK2 pathway in T cell activation and persistence of effector T cells in neuroinflammatory disease. This study predicts that targeting of IFN-gamma(+)/IL-17(+) infiltrating Th cells will be useful for the treatment of multiple sclerosis and other systemic autoimmune diseases.