Shared antigenic determinants between brain and thymus-derived lymphocytes in dogs.

Canine anti-canine myelin, canine distemper convalescent, and control sera were tested for the presence of antilymphocyte antibodies in a complement-dependent microcytotoxicity assay. Sera were cytotoxic for CT 45-S cells, a canine origin thymic lymphoma, canine thymocytes, and phytomitogen-transformed canine peripheral blood lymphocytes. The cytotoxic effect was removed by absorption with canine white matter but not by absorption with galactocerebroside. The data suggests that the specificity of antimyelin and antilymphocyte antibodies is directed toward a common antigen (canine Thy-1). It is likely that, in canine distemper, these antibodies are produced following the lymphotropic phase of viral infection. The possibility that similar autoimmune phenomena observed in multiple sclerosis patients occur via an unrecognized infectious event in lymphoid tissues is raised.