Background and Purpose-Animals subjected to an inflammatory insult at the time of stroke are predisposed to the development of an inflammatory autoimmune response to brain. This response is associated with worse neurological outcome. Because induction of immunologic tolerance to brain antigens before stroke onset is associated with improved outcome, we sought to determine whether this paradigm could prevent the deleterious autoimmune response to brain provoked by an inflammatory stimulus at the time of ischemia. Methods-Male Lewis rats were tolerized to myelin basic protein (MBP) or ovalbumin by intranasal administration before middle cerebral artery occlusion. At the time of reperfusion, all animals received lipopolysaccharide (1 mg/kg intraperitoneal). Behavioral tests were performed at set time intervals. Results-One month after middle cerebral artery occlusion, lymphocytes from the spleens of MBP-tolerized animals were less likely to evidence an autoimmune response and more likely to evidence a regulatory response (TREG) toward MBP than those from ovalbumin-tolerized animals. Animals that had an inflammatory response toward MBP (a TH1 response) performed worse on behavioral tests than those that did not. Fractalkine, a surrogate marker of inflammation, was elevated in animals with a TH1 response to MBP. Conclusions-These data extend our previous findings and suggest that deleterious autoimmunity to brain antigens can be prevented by prophylactically inducing regulatory T-cell responses to those antigens.

Background and purpose Animals subjected to an inflammatory insult with lipopolysaccharide (LPS) at the time of stroke are predisposed to develop a detrimental autoimmune response to myelin basic protein (MBP). In this study, we sought to determine whether other inflammatory stimuli could similarly invoke central nervous system (CNS) autoimmunity and whether these detrimental autoimmune responses occurred to antigens other than MBP. Methods Male Lewis rats underwent 3 h middle cerebral artery occlusion (MCAO) and received intraperitoneal injections of LPS, staphylococcal enterotoxin B (SEB), lipoteichoic acid (LTA) or saline at the time of reperfusion. Behavioral tests were performed at set time intervals after MCAO and animals were sacrificed at 1 month to analyze the immune response to MBP, neuron specific enolase (NSE) and proteolipid protein (PLP). Results Lymphocytes from SEB treated animals were highly reactive to all tested CNS antigens, but treatment with LPS was most likely to lead to a Th1(+) response. A Th1(+) response to MBP, NSE or PLP in spleen was associated with worse outcome, although the response to NSE was most predictive of poor outcome. Animals with a cell mediated autoimmune response to either MBP or NSE in spleen had a concomitant humoral response to these antigens. Conclusions These data show that LPS, but not other inflammatory stimuli, increase the likelihood of developing a detrimental autoimmune response to an array of brain antigens.

BackgroundAn inflammatory insult following middle cerebral artery occlusion (MCAO) is associated with a predisposition to develop a deleterious autoimmune response to the brain antigen myelin basic protein (MBP). Induction of immunologic tolerance to brain antigens prior to MCAO prevents this deleterious autoimmune response and is associated with better functional outcome early after stroke. In this study, we sought to determine the long term immunologic consequences of experimental stroke and induction of mucosal tolerance.MethodsMale Lewis rats were tolerized to MBP or ovalbumin (OVA) by intranasal administration prior to MCAO and administration of lipopolysaccharide (LPS). Neurological outcome was assessed at set points after MCAO and animals sacrificed at 3 months; the immune response to MBP in brain and spleen was determined using ELISPOT assay and degree of cellular inflammatory brain infiltrate assessed by immunocytochemistry.ResultsAnimals that developed a pro-inflammatory (TH1) response to MBP experienced worse outcome, while those that developed a regulatory response (TREG) experienced better outcome. A TREG response in spleen was also associated with decreased inflammation and an increase in the number of FoxP3 positive cells in brain. In this study, tolerization to MBP prior to MCAO was associated with a tendency to develop a TH1 response to MBP by 3 months after MCAO.ConclusionThese data show that induction of immunological tolerance to MBP is associated with improved outcome after stroke. This study, however, raises concern about the potential for inadvertent induction of detrimental autoimmunity through mucosal administration of antigen.