Graft versus host reactions in foals with combined immunodeficiency.

Nine foals with combined immunodeficiency were given hepatic and thymus cells from 68- to 110-day-old (gestational age) fetuses or peripheral blood lymphocytes from nonrelated horses. Clinical signs and lesions consistent with graft vs host reaction were observed in eight of the foals. Diarrhea was observed in these 8 foals, and ulcerative dermatitis, stomatitis, or glossitis was detected in 6 of the 8 foals. Histopathologic changes consisting of necrosis and lymphocyte infiltration were observed in liver, skin, alimentary tract, and less frequently in lymphoid tissues. Changes in complete blood counts, plasma bilirubin concentration, and serum sorbitol dehydrogenase activity were compared with sequential histopathologic alterations in the liver of two combined immunodeficiency foals given peripheral blood lymphocytes from unrelated donor horses. Elevations of sorbitol dehydrogenase correlated with the onset and increasing severity of hepatic lesions.