Progressive myelopathy in older German shepherd dogs. I. Depressed response to thymus-dependent mitogens.

Abstract

Abstract Progressive myelopathy is a spontaneous disease that occurs in older German shepherd dogs. The clinical signs of the disease progress from loss of proprioceptive function to severe posterior ataxia. Pathologic findings include demyelination and axonal degeneration in the spinal cord. Data presented here indicate a marked impairment in the proliferative response to thymus-de-pendent mitogens by peripheral blood leukocytes obtained from dogs with progressive myelopathy. The degree to which proliferative responses were depressed appeared to correspond with the clinical status of the dogs. Serum or plasma obtained from dogs with PM did not suppress the mitogenic response of normal canine leukocytes, and the response to mitogens by PM leukocytes was not restored when the cells were cultured in normal canine serum or plasma. In contrast to the response of peripheral blood leukocytes, spleen and lymph node cells from dogs with progressive myelopathy developed normal proliferative responses to mitogens. Stimulation of proliferation was not detected when cells from dogs with PM were cultured in the presence of myelin basic protein. The relationship between the disease process and the restricted peripheral blood leukocyte deficiency has not been established.