In addition, IFN-β can prevent leukocyte egress from lymph nodes by down-regulating the sphingosine 1-phosphate receptor-1 (S1P1) (Shiow et al., 2006; Gao et al., 2009), and S1P receptor agonists are used to treat MS (Kataoka et al., 2005; Chun and Hartung, 2010; Choi et al., 2011; Galicia-Rosas et al., 2012). Here, S1PR1 is linked to myeloid sarcoma.