Allograft-inflammatory-factor-1 is upregulated in microglial cells in human cerebral infarctions

Allograft inflammatory factor-1 (AIF-1) is a 17-kDa-peptide identified in r at cardiac allografts undergoing chronic rejection and in activated microgl ial cells in inflammatory autoimune disease of the CNS. We have investigate d the expression of AIF-1 in 18 autopsy cases of human focal cerebral infar ction. AIF-1-positive cells show the morphology of microglia and are CD68- but not GFAP-positive. The peptide is expressed at a low level in normal br ain. In infarctions, activated microglial cells in the area of glial reacti on show strongly enhanced cytoplasmic immunoreactivity. The density of AIF- 1-expressing cells increases during the first three days post infarction an d remains elevated until chronic cystic stages. The upregulation of AIF-1-i mmunoreactivity precedes the rise in expression of the S-100-protein MRP-8. We conclude that AIF-1 is a sensitive marker of human microglial activatio n not only in inflammation but also in non-inflammatory. lesions of the CNS . (C) 2000 Elsevier Science B.V. All rights reserved.