CD4 and myeloid sarcoma: It is known that astrocytes play diverse roles in CNS development and disease, but in MS, specifically, astrocytes garner attention for their potential to enhance immune responses through expression of major histocompatibility complex (MHC) class I and class II molecules (Zeinstra et al., 2003; Höftberger et al., 2004) and activation of CD8+ and CD4+ T cells (Sedgwick et al., 1991; Nikcevich et al., 1997; Tan et al., 1998).