Nuclear DNA fragmentation and immune reactivity in bovine spongiform encephalopathy

To investigate whether apoptosis contributes to neuronal degeneration in bo vine spongiform encephalopathy (BSE), morphological changes consistent with apoptosis were sought and in-situ end labelling (ISEL) was applied, in a s eries of 20 BSE cases and 10 age-matched normal control cattle. Apoptotic c hanges were not found in neurons but were occasionally seen in glial cells. Relatively few ISEL-positive neurons were found, but many labelled nuclei were seen in glial cells in certain areas. None of the labelled cells showe d morphological features of apoptosis. ISEL+ cells occurred in areas of spo ngiform change and other areas of grey matter lacking spongiform change. So me association was found between degree of cellular DNA fragmentation and a ccumulation of abnormal prion protein (PrPSc). Interestingly, small or mode rate numbers of T lymphocytes, not present in the normal central nervous sy stem (CNS), were detected in the CNS parenchyma in most BSE cases. There wa s a pronounced astrogliosis, but markers of macrophage or microglial activa tion were only slightly increased. The results indicate that nuclear DNA vu lnerability is enhanced in certain neuroanatomical areas in BSE, but eviden ce that apoptosis plays a role in neuronal loss in BSE was very limited. (C ) 1999 Harcourt Publishers Ltd.