Mig and IP-10 are related members of the CXC subfamily of the chemokine family of cytokines. The murine Mig (MuMig), human IP-10, and the mouse homologue of IP-10, Crg-2, were all identified due to the dramatic inductions of their genes in monocytic cells treated with interferon-gamma (IFN-gamma). Studies using recombinant (r) human proteins show that, unlike most other CXC chemokines, rHuMig and rIP-10 have no activity on neutrophils but appear to target lymphocytes specifically. rHuMig and rIP-10 are active as chemotactic factors for stimulated, but not for resting, T cells. Studies done in vitro and in vivo have shown that rHuMig and rIP-10 share additional activities, including inhibition of neovascularization, inhibition of hematopoietic progenitor cells, and anti-tumor effects. rHuMig and rIP-10 show reciprocal desensitization on activated T cells and have been demonstrated to share a receptor, CXCR3. The genes for both MuMig and Crg-2 are highly expressed in multiple tissues during experimental viral and protozoan infections in mice, but their patterns of expression differ. This suggests that the Migs and IP-10/Crg-2 may play roles in host defense and that, despite their similar activities assayed in vitro, Mig and IP-10/Crg-2 may serve non-redundant functions in vivo.