Neurovascular fibrinolytic activity in normal Lewis rats and rats with cell-transferred experimental allergic encephalomyelitis

Fibrinolytic activity in the form of plasminogen activator (PA) was assessed using a histochemical fibrin slide technique in spinal cords of normal Lewis rats and rats with the cell-transferred from of experimental allergic encephalomyelitis (EAE). PA was localized exclusively to blood vessels. Vessels in the leptomeninges had maximum activity. A precipitous decrease in PA activity occured in recipient rats which coincided with onset of clinical neurologic signs. A subsequent return in activity occured in association with clinical remission of disease but remained well below the activity of normal rats for as long as the recipient animals were followed. Vessels containing perivascular cellular infiltrates of EAE had little or no detectable PA activity. Furthermore, PA could not be demonstrated to be associated with infiltrating inflammatory cells, including macrophages. These findings provide further support for involvement of the coagulation and fibrinolytic ssytems in the early clinical manifestation of EAE in Lewis rats.