EPHA4 and multiple sclerosis: Interpretation of the role of Arginase 1 expressing macrophages following CNS injury in our model is complicated by the fact that, while EphA4 has not been associated with myeloid or monocyte development, EphA4 protein has been localised to macrophages in human lung [48] and multiple sclerosis lesions [19] and other Eph receptors and ephrin ligands are expressed in monocytes and macrophages [10], [19].