Recent studies have shown that T cells expressing CCR5 and CXCR3 can be detected within perivascular lesions of brains with MS [Simpson et al. 1998; Balashov et al. 1999; Sorensen et al. 1999], and T cells expressing these receptors are increased in cerebrospinal fluid (CSF) compared with peripheral blood [Kivisakk et al. 2002; Sorensen et al. 1999, 2002; Teleshova et al. 2002]. Here, CCR5 is linked to myeloid sarcoma.