Probable role of immunological tolerance to ischemia injury in brain

To address the issues of immunological tolerance to ischemia injury in the brain we have researched ischemic stroke patients with and without prodromal transitional ischemic attacks (TIAs) for several blood acute phase reactants involved in inflammatory reactions in respect to initial infarct size, clinical course of disease and functional outcome at 1 month. The study involved 54 ischemic stroke patients aged 45 to 70 years, 46 female and 38 male admitted within 24 hours of symptoms onset in neurological clinic of Georgian State Medical University during 2000-2006. Exclusion criteria comprised severe somatic pathology, liver and renal dysfunctions. Control subjects were aged-matched 15 healthy volunteers, who did not reveal any significant signs of cerebrovascular disease according to the anamnesis, clinical and instrumental investigations. Etiology of stroke was classified according to TOAST criteria. Patients were divided into three groups: the first group - 22 patients with first-ever stroke, the second -17 patients with prodromal TIAs from one to three months before stroke and the third - 15 patients with prodromal TIAs within 4 weeks before stroke. Initial neurological impairment assessed immediately after admission by NIHSS score. All three groups selected with the same initial severity of stroke with mean NIHSS score = 12+/-3.5; for evaluation of clinical course of disease patients were assessed by NIHSS on 7th day of stroke. In 48 hours from stroke onset the blood levels of (IL-1beta, IL-6, TNF-alpha, IL-10) were significantly elevated against control (p<0.05). At this time, no statistical differences were detected between groups regarding the initial blood levels of IL-1beta and TNF-alpha, while the level of IL-6 was significantly lower in the third group (p<0.05). Blood contents of IL-10 and TGF-beta1 found to be non-significantly elevated in the third group against two other groups, while blood TGF-beta1 was significantly increased compared to control. Significant positive correlation was found between IL-6 blood contents and clinical course of disease (r=+0.32, p<0.05). Multivariate logistic regression found the significance of initial blood IL-6 contents for probability of stroke functional outcome at 1 month. It can be supposed that relatively mild blood inflammatory response in third group can be related to occurring of immunological tolerance.