LYMPHOCYTIC INFILTRATION AND EXPRESSION OF INTERCELLULAR-ADHESION MOLECULE-1 IN PHOTOCHEMICALLY INDUCED ISCHEMIA OF THE RAT CORTEX

The contribution of the immune system to the pathogenesis of ischemic lesions is still uncertain. We have analyzed leukocyte infiltration in photochemically induced focal ischemia of the rat parietal cortex by immunocytochemistry. Between 1 and 2 days after photothrombosis, CD5T cells adhered to subpial and cortical vessels and infiltrated the is chemic lesion prior to macrophages. By day 3 numerous T cells and some macrophages, whose number increased further between day 3 and day 7, had infiltrated the border zone around the lesion sparing the center. In addition, CD5-/CD8+ lymphocytes that probably represent natural kil ler cells were found. Intercellular adhesion molecule-1 (ICAM-1) was e xpressed on endothelial cells on days 1 and 2 and in the border zone o n infiltrating leukocytes from day 3 to day 7. Starting on day 7, macr ophages infiltrated the core of the lesion to remove debris. When the entire lesion was covered by macrophages at day 14, the number of T ce lls had decreased and ICAM-1 immunoreactivity was no longer found in o r around the infarct. In conclusion, our study shows that ischemic les ions can lead to a local immune reaction in the CNS. Thus, blocking of lymphocyte-derived cytokines or cell adhesion molecules may provide a new approach to confining the sequelae of stroke.