A method of detecting an agent that modulates the activity of CCRL2, the method comprising: (a) contacting a CCRL2 polypeptide with a macrophage inflammatory protein-4 (MIP-4) polypeptide in the presence of a candidate agent under conditions, which in the absence of the test agent, permit the binding of the MIP-4 polypeptide to the CCRL2 polypeptide; and (b) determining whether the candidate agent is capable of modulating the interaction between said CCRL2 polypeptide and said MIP-4 polypeptide.