Ultrastructural findings in the mouse exocrine pancreas during graft-versus host reaction.

12- to 36-hours-old newborn CBA mice were intraperitoneally injected each with 10 X 10(6) allogeneic spleen cells of adult C57Bl mice. Control mice received syngeneic spleen cells of adult CBA mice either in the same way or remained untreated. The animals were killed 1, 3, 7, 14 or 21 days after the spleen cell injection. The pancreas was studied histologically and electron microscopically by common methods. Together with an interstitial lymphohistiocytic infiltration of the pancreas different acinar cell alterations were observed in the mice treated with allogeneic spleen cells: 1. Acute lethal pancreatic cell damages on the day after the intraperitoneal injection of allogeneic spleen cells. 2. Membrane-lined inclusion vacuoles between the 7th and 21st experimental day. 3. Atrophy of pancreatic acinar cells in the terminal stage of a severe graft-versus-host disease. The pathogenesis of the observed pancreatic changes seems to be due to nonimmunological and immunological processes. The membrane-lined inclusion vacuoles of the acinar cells could be the consequence of a cell-mediated immune process in the graft-versus-host reaction.