EPHA4 and myeloid sarcoma: Given that Eph-ephrin interactions and the expression of EphA4 specifically, may contribute to the pathology of MS and EAE in a number of ways, including effects in the immune system, a glial cell response and axonal damage, in this manuscript we have assessed the role of EphA4 in regulating EAE severity and development by use of EphA4 knockout animals and blocking of EphA4 using a decoy receptor.