IL1B and myeloid sarcoma: The present study is the first to demonstrate that during the early clinical phases of experimental MS, i.e. cr-EAE, IL-1β and IL-1ra mRNA and protein are not only expressed in white matter, but also in specific grey matter areas within the CNS, which are also positive for CD68 and Oil-Red O. The IL-1β and IL-1ra mRNA expressing cells were identified as macrophages and/or endogenous activated microglial cells.