LOCAL IMMUNE-RESPONSES IN THE RAT CEREBRAL-CORTEX AFTER MIDDLE CEREBRAL-ARTERY OCCLUSION

This study describes local immune responses in cerebral ischemia induc ed by permanent occlusion of the middle cerebral artery (MCAO) in the rat. The temporal and spatial pattern of leukocyte infiltration was ch aracterized immunocytochemically using monoclonal antibodies against C D5, a pan T cell marker, against CD4 and CD8 for subtyping of T lympho cytes, and ED1, a marker for macrophages. CD5(+) T cells were present in some animals on the pial surface at day 1 and with increasing numbe rs mainly at the edges of the infarcts at days 3 and 7. By day 14 thei r number had significantly decreased. Subtyping of T lymphocytes revea led that CD4(+) helper/inducer T cells were rare, while CD8(+) lymphoc ytes were abundant. Moreover, CD8(+) lymphocytes outnumbered CD5(+) T cells indicating the presence of CD5(-)/CD8(+) natural killer (NK) cel ls. ED1(+) macrophages primarily infiltrated the core of the infarct s tarting on,day 1. Infiltrating leukocytes expressed leukocyte function associated antigen-1 and MHC class I and II antigens. Early after inf arction, increased expression of the intercellular adhesion molecule-1 was found on vessels and leukocytes. In conclusion, this study shows that lymphocytes enter the nervous system not only in autoimmune disea ses, but also in response to primarily 'non-immune' neuronal damage su ch as stroke.