CCL2 and Splenomegaly: Pardanani et al. [16] observed that high circulating levels of MCP-1, IL-2R, IL-8, and IL-15 were associated with poor anemia response, and that elevated levels of MCP-1, sIL-2R, and IL-15 were clustered with splenomegaly in myelofibrosis (both PMF and post PV/ET MF).