PHENOTYPIC CHARACTERIZATION OF THE CELLS OF THE INFLAMMATORY RESPONSEIN OVINE ENCEPHALITIC LISTERIOSIS

The brainstem (pens cerebri and medulla oblongata) of 22 sheep aged be tween 6 months and 3 years which had developed clinical signs of centr al nervous system dysfunction were examined. Histopathological changes characterized by microabscesses, focal gliosis and perivascular cuffi ng compatible with natural infection with Listeria monocytogenes were present. The brains were examined by lectin histochemistry and immunoh istochemistry with markers for T lymphocytes (CD4(+) and CD8(+) subset s), B lymphocytes, mononuclear phagocytes (including macrophages, rami fied microglia, activated microglia and amoeboid microglia), astroglia and L. monocytogenes. These methods allowed semiquantitative analyses of the frequency of the different cell types in the brain lesions. Th e distribution of listerial antigen in the lesions was variable but al ways sparse. Mononuclear phagocytes and neutrophils appeared to be the most numerous inflammatory cells in the affected areas of the brainst em. T lymphocytes (CD8(+) and CD4(+) subsets) and B lymphocytes also p layed a part in the inflammatory process, in addition to activated ast rocytes. (C) 1995 Academic Press Limited