Hepatic fibrosis represents the generalized response of the liver to injury and is characterized by excessive deposition of extracellular matrix. The cellular basis of this process is complex and involves interplay of many factors, of which cytokines are prominent. We have identified divergent fibrosing responses to injury among mouse strains and taken advantage of these differences to examine and contrast T helper (Th)-derived cytokines during fibrogenesis. Liver injury was induced with carbon tetrachloride, fibrosis was quantitated, and Th1͞Th2 cytokine mRNAs measured. Liver injury in BALB͞c mice resulted in severe fibrosis, whereas C57BL͞6 mice developed comparatively minimal fibrosis. Fibrogenesis was significantly modified in T and B celldeficient BALB͞c and C57BL͞6 severe combined immunodeficient (SCID) mice compared with wild-type counterparts, suggesting a role of Th subsets. Fibrogenic BALB͞c mice exhibited a Th2 response during the wounding response, whereas C57BL͞6 mice displayed a Th1 response, suggesting that hepatic fibrosis is inf luenced by different T helper subsets. Moreover, mice lacking interferon ␥, which default to the Th2 cytokine pathway, exhibited more pronounced fibrotic lesions than did wild-type animals. Finally, shifting of the Th2 response toward a Th1 response by treatment with neutralizing anti-interleukin 4 or with interferon ␥ itself ameliorated fibrosis in BALB͞c mice. These data support a role for immune modulation of hepatic fibrosis and suggest that Th cytokine subsets can modulate the fibrotic response to injury.

Insulin-like growth factor-binding protein (IGFBP)-3 binds the insulin-like growth factors with high affinity and modulates their actions. Proteolytic cleavage of IG-FBP-3 may regulate insulin-like growth factor bioavailability. IGFBP-3 is extensively degraded in serum during pregnancy; however, as yet the pregnancy-specific protease, or proteases, have not been identified. We utilized a yeast two-hybrid assay and a human placental cDNA library to investigate IGFBP-3-interacting proteins. A disintegrin and metalloprotease-12 (ADAM 12), a member of a family of metalloprotease disintegrins that is highly expressed in placental tissue, was identified as interacting with IGFBP-3. This interaction involved the cysteine-rich domain of ADAM 12. Unlike other members of this family of disintegrin metalloproteases that are membrane proteins, ADAM 12 exists as an alternatively spliced soluble secreted protein. To verify the interaction between ADAM 12 and IGFBP-3, an expression construct containing an ADAM 12-S cDNA was transfected into COS-1 cells. Co-precipitation was observed when conditioned medium was analyzed by immunoprecipitation with an antibody against either ADAM 12 or IGFBP-3 followed by Western blotting with anti-IG-FBP-3 or anti-ADAM 12. Although minimal proteolysis of IGFBP-3 was observed in conditioned medium from control cells, this was increased ϳ4-fold in conditioned medium from ADAM 12-S-transfected cells. Recombinant ADAM 12-S partially purified from conditioned medium on a heparin-Sepharose column also proteolyzed IG-FBP-3. The degradation pattern was similar to that seen with pregnancy serum, and the presence of ADAM 12-S in serum during pregnancy was confirmed. The data suggest that ADAM 12-S has IGFBP-3 protease activity, and it may contribute to the IGFBP-3 protease activity present in pregnancy serum.