HISTOLOGICAL-CHANGES OF THE LIVER IN EXPERIMENTAL GRAFT-VERSUS-HOST DISEASE ACROSS MINOR HISTOCOMPATIBILITY BARRIERS .8. ROLE OF EOSINOPHILINFILTRATION

Although eosinophil infiltrate has been recognized in hepatic graft-ve rsus-host disease, its significance in relation to hepatic graft-versu s-host disease lesions is unknown. In the present study, we analyzed h epatic eosinophil infiltration in relation to bile duct damage in expe rimental mouse graft-versus-host disease across minor histocompatibili ty barriers up to 14 months after transplantation. Portal eosinophil i nfiltration was found from 1 week after transplantation throughout the entire 14-month observation period. It was most striking during the e arly chronic stage of hepatic graft-versus-host disease between 2 to 7 months, with a peak at 5 months after transplantation. Microscopic an d electron microscopic study revealed eosinophils infiltrated around t he bile duct as well as in the bile duct epithelial layer. They were c ommonly found together with lymphocytes but were also occasionally fou nd singly around the bile duct and in the bile duct epithelial layer, Bile duct epithelial cells in contact with and in the vicinity of eosi nophils showed a variety of degenerative changes, occasionally associa ted with the presence of extracellular eosinophil granules. Bile duct epithelial cells with eosinophil infiltration just beneath the basemen t membrane frequently showed further characteristic severe degenerativ e changes with shedding or dropping-off into the lumen, which features were quite similar to those seen in the bronchial epithelium in asthm a patients. These results indicate that not only lymphocytes but also eosinophils may be involved in the production of the bile duct injury in hepatic graft-versus-host disease, especially in its early chronic stage.