DYNAMICS OF MICROGLIAL ACTIVATION IN THE SPINAL-CORD AFTER CEREBRAL INFARCTION ARE REVEALED BY EXPRESSION OF MHC CLASS-II ANTIGEN

Microglial reactivity associated with induction of MHC class II (HLA-D R) antigen is a sensitive indicator for pathological events in the CNS . To assess the response of glial cells after lesions of supraspinal d escending tracts, HLA-DR, CD68 and GFAP were studied immunohistochemic ally on spinal cord tissue of 5 patients who died after unilateral inf arction of the middle cerebral artery territory, and 5 control cases. In patients who died shortly after a stroke (4-14 days) increased HLA- DR-immunoreactivity (HLA-DR-IR) could be observed in the intermediate grey matter and in the ventral horn. The CD68-IR was much less intense . After longer survival times (5 weeks to 4 months), HLA-DR-IR in the grey matter was clearly lower than that observed in the spinal cord of short survival times, but very abundant in the dorsolateral funiculus , specifically within the corticospinal tract. In white matter areas, CD68-IR was almost identical to the HLA-DR-IR. Within the grey matter, CD68-IR was similar to the control tissue. A moderate increase of GFA P-positive astrocytes could be seen only in the grey matter after long er survival times. It seems probable, that the dynamics of HLA-DR-posi tive microglia reflect the early phagocytosis of presynaptic terminals by microglia in target regions of descending fibre tracts. In the whi te matter, the removal of degenerating axons by phagocytosing microgli a expressing HLA-DR and CD68 antigens is a slower process which occurs over a period of months.