Hematogenous cells in experimental Japanese encephalitis.

Four adult mice were injected with 3H-thymidine repeatedly so that in their brains only circulating blood cells were labelled with 3H-thymidine. They then received an intracerebral injection of Japanese encephalitis virus, were sacrified on the 3rd, 4th and 5th day after inoculation: the brains were examined by light and electron microscopic autoradiography. Inflammatory cells appearing in the brain parenchyma and perivascularly in the acute stage of the experimental Japanese encephalitis are derived from circulating mononuclear leukocytes. They assume the shape of "rod cells" and are the main constituents of the "glial nodule" in the brain parenchyma. Their fine structural characteristics are discussed.