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Background: Dendritic cells (DCs) regulate the immune response associated with T lymphocytes, but their role in stroke remains unclear. In this study, we investigated the causal relationship between DCs and T-cell response in intracerebral hemorrhage (ICH) by focusing on TLRs (toll-like receptors) that may modulate the function of DCs., Methods: We studied the effects of TLR4, TLR2, and TLR9 on DC-mediated T-cell response and the outcomes of ICH using male C57BL/6 and CD11c-DTx (diphtheria toxin) receptor mice. We administered specific agents intraperitoneally or orally and evaluated the results using flow cytometry, real-time polymerase chain reaction, Western blotting, immunofluorescence staining, histopathology, and behavioral tests., Results: TLR4 and TLR2 activation induces DC maturation and reduces the ratio of regulatory T to T-helper 17 cells in the brain and periphery after ICH. When either of these receptors is activated, it can worsen neuroinflammation and exacerbate ICH outcomes. TLR9 also promotes DC maturation, stabilizing the number of DCs, particularly conventional DCs. TLR9 has the opposite effects on regulatory T/T-helper 17 balance, neuroinflammation, and ICH outcomes compared with TLR4 and TLR2. Upon stimulation, TLR4 and TLR9 may achieve these effects through the p38-MAPK (p38-mitogen-activated protein kinase)/MyD88 (myeloid differentiation primary response gene 88) and indoleamine 2,3-dioxygenase 1 (IDO1)/GCN2 (general control nonderepressible 2) signaling pathways, respectively. DCs act as intermediaries for TLR-mediated T-cell response., Conclusions: TLR-mediated opposing effects of DCs on T-cell response may provide novel strategies to treat ICH., Competing Interests: None.

Background and Purpose: Spontaneous intracerebral hemorrhage (sICH) is a common form of hemorrhagic stroke, with high mortality and morbidity. Pathophysiological mechanisms in sICH are poorly understood and treatments limited. Neuroinflammation driven by microglial-macrophage activation contributes to brain damage post-sICH. We aim to test the hypothesis that an anti-inflammatory (repair) process occurs in parallel with neuroinflammation in clinical sICH., Methods: We performed quantitative analysis of immunohistochemical markers for microglia and macrophages (Iba1, CD68, TMEM119, CD163, and CD206) in brain tissue biospecimens 1 to 12 days post-sICH and matched control cases. In a parallel, prospective group of patients, we assayed circulating inflammatory markers (CRP [C-reactive protein], total white cell, and monocyte count) over 1 to 12 days following sICH., Results: In 27 supratentorial sICH cases (n=27, median [interquartile range] age: 59 [52–80.5], 14F/13M) all microglia-macrophage markers increased post-sICH, relative to control brains. Anti-inflammatory markers (CD163 and CD206) were elevated alongside proinflammatory markers (CD68 and TMEM119). CD163 increased progressively post-sICH (15.0-fold increase at 7–12 days, P<0.001). CD206 increased at 3 to 5 days (5.2-fold, P<0.001) then returned to control levels at 7 to 12 days. The parenchymal immune response combined brain-derived microglia (TMEM119 positive) and invading monocyte-derived macrophages (CD206 positive). In a prospective sICH patient cohort (n=26, age 74 [66–79], National Institutes of Health Stroke Scale on admission: 8 [4–17]; 14F/12M) blood CRP concentration and monocyte density (but not white blood cell) increased post-sICH. CRP increased from 0 to 2 to 3 to 5 days (8.3-fold, P=0.020) then declined at 7 to 12 days. Monocytes increased from 0 to 2 to 3 to 5 days (1.8-fold, P<0.001) then declined at 7 to 12 days., Conclusions: An anti-inflammatory pathway, enlisting native microglia and blood monocytes, occurs alongside neuroinflammation post-sICH. This novel pathway offers therapeutic targets and a window of opportunity (3–5 days post-sICH) for delivery of therapeutics via invading monocytes.

Background and Purpose- Microglia are among the first cells to respond to intracerebral hemorrhage (ICH), but the mechanisms that underlie their activity following ICH remain unclear. IL (interleukin)-15 is a proinflammatory cytokine that orchestrates homeostasis and the intensity of the immune response following central nervous system inflammatory events. The goal of this study was to investigate the role of IL-15 in ICH injury. Methods- Using brain slices of patients with ICH, we determined the presence and cellular source of IL-15. A transgenic mouse line with targeted expression of IL-15 in astrocytes was generated to determine the role of astrocytic IL-15 in ICH. The expression of IL-15 was controlled by a glial fibrillary acidic protein promoter (GFAP-IL-15 tg ). ICH was induced by intraparenchymal injection of collagenase or autologous blood. Results- In patients with ICH and wild-type mice subjected to experimental ICH, we found a significant upregulation of IL-15 in astrocytes. In GFAP-IL-15 tg mice, we found that astrocyte-targeted expression of IL-15 exacerbated brain edema and neurological deficits following ICH. This aggravated ICH injury in GFAP-IL-15 tg mice is accompanied by increased microglial accumulation in close proximity to astrocytes in perihematomal tissues. Additionally, microglial expression of CD86, IL-1β, and TNF-α is markedly increased in GFAP-IL-15 tg mice following ICH. Furthermore, depletion of microglia using a colony stimulating factor 1 receptor inhibitor diminishes the exacerbation of ICH injury in GFAP-IL-15 tg mice. Conclusions- Our findings identify IL-15 as a mediator of the crosstalk between astrocytes and microglia that exacerbates brain injury following ICH.

Background and Purpose: Although preclinical studies have shown inflammation to mediate perihematomal edema (PHE) after intracerebral hemorrhage, clinical data are lacking. Leukocyte count, often used to gauge serum inflammation, has been correlated with poor outcome but its relationship with PHE remains unknown. Our aim was to test the hypothesis that leukocyte count is associated with PHE growth., Methods: We included patients with intracerebral hemorrhage admitted to a tertiary-care stroke center between 2011 and 2015. The primary outcome was absolute PHE growth during 24 hours, calculated using semiautomated planimetry. Linear regression models were constructed to study the relationship between absolute and differential leukocyte counts (monocyte count and neutrophil-lymphocyte ratio) and 24-hour PHE growth., Results: A total of 153 patients were included. Median hematoma and PHE volumes at baseline were 14.4 (interquartile range, 6.3-36.3) and 14.0 (interquartile range, 5.9-27.8), respectively. In linear regression analysis adjusted for demographics and intracerebral hemorrhage characteristics, absolute leukocyte count was not associated with PHE growth (β, 0.07; standard error, 0.15; P =0.09). In secondary analyses, neutrophil-lymphocyte ratio was correlated with PHE growth (β, 0.22; standard error, 0.08; P =0.005)., Conclusions: Higher neutrophil-lymphocyte ratio is independently associated with PHE growth. This suggests that PHE growth can be predicted using differential leukocyte counts on admission., (© 2017 American Heart Association, Inc.)

Background and Purpose: Intracerebral hemorrhage (ICH) is a neurologically destructive stroke, for which no valid treatment is available. This preclinical study examined the therapeutic effect of PD-L1 (programmed death ligand 1), a B7 family member and a ligand for both PD-1 (programmed death 1) and B7-1 (CD80), in a murine ICH model., Methods: ICH was induced by injecting autologous blood into 252 male C57BL/6 and Rag1 -/- mice. One hour later, ICH mice were randomly assigned to receive an intraperitoneal injection of vehicle, PD-L1, or anti-PD-L1 antibody. Neurological function was assessed along with brain edema, brain infiltration of immune cells, blood-brain barrier integrity, neuron death, and mTOR (mammalian target of rapamycin) pathway products., Results: PD-L1 significantly attenuated neurological deficits, reduced brain edema, and decreased hemorrhage volume in ICH mice. PD-L1 specifically downsized the number of brain-infiltrating CD4 + T cells and the percentages of Th1 and Th17 cells but increased the percentages of Th2 and regulatory T cells. In the PD-L1-treated group, we observed an amelioration of the inflammatory milieu, decreased cell death, and enhanced blood-brain barrier integrity. PD-L1 also inhibited the mTOR pathway. The administration of anti-PD-L1 antibody produced the opposite effects to those of PD-L1 in ICH mice., Conclusions: PD-L1 provided protection from the damaging consequences of ICH., (© 2017 American Heart Association, Inc.)

Background and Purpose: Preclinical studies and a proof-of-concept clinical study have shown that sphingosine-1-phosphate receptor (S1PR) modulator, fingolimod, improves the clinical outcome of intracerebral hemorrhage (ICH). However, the specific subtype of the S1PRs through which immune modulation provides protection in ICH remains unclear. In addition, fingolimod-induced adverse effects could limit its use in patients with stroke because of interactions with other S1PR subtypes, particularly with S1PR3. RP101075 is a selective S1PR1 agonist with superior cardiovascular safety profile. In this study, we investigated the impact of RP101075 treatment in a mouse model of ICH., Methods: ICH was induced by injection of autologous blood in 294 male C57BL/6J and Rag2(-/-) mice. ICH mice randomly received vehicle, RP101075, or RP101075 plus S1PR1 antagonist W146 by daily oral gavage for three consecutive days, starting from 30 minutes after surgery. Neurodeficits, brain edema, brain infiltration of immune cells, blood-brain barrier integrity, and cell death were assessed after ICH., Results: RP101075 significantly attenuated neurological deficits and reduced brain edema in ICH mice. W146 blocked the effects of RP101075 on neurodeficits and brain edema. RP101075 reduced the counts of brain-infiltrating lymphocytes, neutrophils, and microglia, as well as cytokine expression after ICH. Enhanced blood-brain barrier integrity and alleviated neuronal death were also seen in ICH mice after RP101075 treatment., Conclusions: S1PR1 modulation via RP101075 provides protection in experimental ICH. Together with the advantageous pharmacological features of RP101075, these results warrant further investigations of its mechanisms of action and translational values in ICH patients., (© 2016 American Heart Association, Inc.)

Background and Purpose: Secondary intracerebral hemorrhage (sICH) is a potentially serious complication of ischemic stroke, in particular under concomitant oral anticoagulation. Previous studies in murine stroke models defined a novel vascular repair function of hematogenous monocytes/macrophages (MO/MP), which proved essential for the prevention of oral anticoagulation-associated sICH. Here, we addressed the question whether hyperglycemia as a clinically relevant prohemorrhagic risk factor and peroxisome proliferator-activated receptor gamma (PPARγ) activation affect MO/MP differentiation and the risk of sICH after ischemic stroke., Methods: Oral anticoagulation-associated sICH was induced by phenprocoumon feeding to mice undergoing transient middle cerebral artery occlusion. Hyperglycemia was induced by streptozotocin treatment. The role of PPARγ-dependent MO/MP differentiation was addressed in mice with myeloid cell-specific PPARγ-knockout (LysM-PPARγ(KO)). Pharmacological PPARγ activation via pioglitazone was tested as a treatment option., Results: Hyperglycemic mice and normoglycemic LysM-PPARγ(KO) mice exhibited abnormal proinflammatory skewing of their hematogenous MO/MP response and abnormal vascular remodeling in the infarct border zone, leading to an increased rate of oral anticoagulation-associated sICH. Pharmacological PPARγ activation in hyperglycemic mice corrected the inflammatory response toward an anti-inflammatory profile, stabilized neovessels in the infarct border zone, and reduced the rate of sICH. This preventive effect was dependent on the presence of macrophages, but independent from effects on blood glucose levels., Conclusions: Hyperglycemia and macrophage-specific PPARγ activation exert opposing effects on MO/MP polarization in ischemic stroke lesions and, thereby, critically determine the risk of hemorrhagic infarct transformation., (© 2015 American Heart Association, Inc.)

Background and Purpose: Inflammatory responses and blood-brain barrier (BBB) dysfunction play important roles in brain injury after intracerebral hemorrhage (ICH). The metalloprotease ADAMTS 13 (a disintegrin and metalloprotease with thrombospondin type I motif, member 13) was shown to limit inflammatory responses through its proteolytic effects on von Willebrand factor. In the present study, we addressed the role of ADAMTS 13 after experimental ICH., Methods: ICH was induced in mice by intracerebral infusion of autologous blood. The peri-hematomal inflammatory responses, levels of matrix metalloproteinase-9 and intercellular adhesion molecule-1, pericyte coverage on brain capillaries, and BBB permeability were quantified at 24 hours. Functional outcomes, cerebral edema, and hemorrhagic lesion volume were quantified at day 3., Results: Treatment with recombinant ADAMTS 13 (rADAMTS 13) reduced the levels of chemokines and cytokines, myeloperoxidase activity, and microglia activation and neutrophil recruitment after ICH. rADAMTS 13 also decreased interleukin-6 expression in brain endothelial cells stimulated by lipopolysaccharide, whereas recombinant von Willebrand factor reversed this effect. The anti-inflammatory effect of rADAMTS 13 was accompanied by reduced expression of intercellular adhesion molecule-1 and less activation of matrix metalloproteinase, enhanced pericyte coverage of brain microvessels, and attenuated BBB disruption. Furthermore, neutrophil depletion protected against BBB damage, and rADAMTS 13 treatment had no further beneficial effect. Finally, treatment of mice with rADAMTS 13 reduced cerebral edema and hemorrhagic lesion volume and improved neurological functions., Conclusions: Our findings reveal the importance of rADAMTS 13 in regulating pathological inflammation and BBB function and suggest that rADAMTS 13 may provide a new therapeutic strategy for ICH., (© 2015 American Heart Association, Inc.)

Background and Purpose: Intracerebral hemorrhage (ICH) is swiftly followed by an inflammatory response. A key component of this response is the recruitment of leukocytes into the brain, which promotes neurological injury in rodent models. However, the mechanisms by which leukocytes transmigrate across the endothelium into the injured brain are unclear. The present study examines leukocyte adhesion molecules (α4 integrin, L-selectin, and αLβ2 integrin) on 4 leukocyte subtypes to determine which are important for leukocyte recruitment after ICH., Methods: We used the blood injection mouse model of ICH, whereby 25 μL of blood was injected into the striatum. Flow cytometry was used to quantify leukocyte populations and adhesion molecule expression in brain and blood. An α4 integrin-blocking antibody was administered to evaluate the contribution of α4 integrin in leukocyte migration and neurological injury., Results: α4 integrin was elevated on all leukocyte populations in brain after ICH, whereas L-selectin was unchanged and αLβ2 was increased only on T cells. Antagonism of α4 resulted in decreased leukocyte transmigration and lessened neurobehavioral disability., Conclusions: α4 integrin is an important cell adhesion molecule involved in neuroinflammation after ICH., (© 2014 American Heart Association, Inc.)

Background and Purpose: Minimizing hematoma growth in high-risk patients is an attractive strategy to improve outcomes after intracerebral hemorrhage. We tested the hypothesis that desmopressin (DDAVP), which improves hemostasis through the release of von Willebrand factor, improves platelet activity after intracerebral hemorrhage., Methods: Patients with reduced platelet activity on point-of-care testing alone (5), known aspirin use alone (1), or both (8) received desmopressin 0.4 μg/kg IV. We measured Platelet Function Analyzer-epinephrine (Siemens AG, Germany) and von Willebrand factor antigen from baseline to 1 hour after infusion start and hematoma volume from the diagnostic to a follow-up computed tomographic scan., Results: We enrolled 14 patients with of mean age 66.8±14.6 years, 11 (85%) of whom were white and 8 (57%) were men. Mean Platelet Function Analyzer-epinephrine results shortened from 192±18 seconds pretreatment to 124±15 seconds (P=0.01) 1 hour later, indicating improved plate activity. von Willebrand factor antigen increased from 242±96% to 289±103% activity (P=0.004), indicating the expected increase in von Willebrand factor. Of 7 (50%) patients who received desmopressin within 12 hours of intracerebral hemorrhage symptom onset, changes in hematoma volume were modest, -0.5 (-1.4 to 8.4) mL and only 2 had hematoma growth. One patient had low blood pressure and another had a new fever within 6 hours of desmopressin administration., Conclusions: Intravenous desmopressin was well tolerated and improved platelet activity after acute intracerebral hemorrhage. Larger studies are needed to determine its potential effects on reducing hematoma growth versus platelet transfusion or placebo., Clinical Trial Registration Url: http://www.clinicaltrials.gov. Unique identifier: NCT00961532., (© 2014 American Heart Association, Inc.)

Background and Purpose: The aging brain demonstrates frequent MRI and pathological evidence of cerebral microbleeds, which are often associated with cerebral amyloid angiopathy. To develop new therapeutic strategies for this disorder, we studied cerebral microhemorrhage in a well-characterized mouse model of cerebral amyloid angiopathy., Methods: Tg2576 mice were studied at ages ranging from 2 to 21 months. Spontaneous and induced microscopic bleeding was analyzed with and without a passive anti-amyloid immunization regimen and dietary supplementation of ischemic stroke prevention medication dipyridamole., Results: Areas of microhemorrhage were easily demonstrated and were significantly more prominent in the oldest mice and in animals treated with anti-amyloid immunotherapy. Dipyridamole supplementation in the diet generated plasma levels >790 ng/mL within the range seen clinically. Dipyridamole treatment did not worsen frequency and size of cerebral microscopic bleeding., Conclusions: The Tg2576 mouse is a useful model to study progression and modification of spontaneous and immunotherapy-induced cerebral microhemorrhage. Absence of microhemorrhage worsening with dipyridamole treatment suggests a potential therapeutic role of this agent when ischemic and microhemorrhagic lesions coexist.

Background and Purpose: There are few reports on proinflammatory cytokines and risk of primary or recurrent stroke. We studied the association of interleukin (IL)-6, IL-18, and tumor necrosis factor-alpha (TNF-alpha) with recurrent stroke in a nested case-control study derived from the Perindopril Protection Against Recurrent Stroke Study (PROGRESS)., Methods: We performed a nested case-control study of 591 strokes (472 ischemic, 83 hemorrhagic, 36 unknown subtype) occurring during a randomized, placebo-controlled multicenter trial of perindopril-based therapy in 6105 patients with a history of stroke or transient ischemic attack. Controls were matched for age, treatment group, sex, region, and most recent qualifying event at entry to the parent trial., Results: IL-6 and TNF-alpha, but not IL-18, were associated with risk of recurrent ischemic stroke independently of conventional risk markers. Adjusted odds ratios comparing the highest to lowest third of their distributions were 1.33 (95% CI, 1.00 to 1.78) for IL-6 and 1.46 (1.02 to 2.10) for TNF-alpha. No inflammatory marker was associated with hemorrhagic stroke risk. In multivariable models, IL-6 and TNF-alpha fully explained observed associations of C-reactive protein and fibrinogen with risk of ischemic stroke, but TNF-alpha retained borderline significance after full adjustment., Conclusions: Inflammatory markers associated with the acute-phase response (IL-6, TNF-alpha, C-reactive protein, and fibrinogen, but not IL-18) are associated with risk of recurrent stroke. These markers are dependent on each other in multivariable models, and once all were included, only TNF-alpha retained a borderline association. Markers of generalized inflammation of the acute-phase response are associated with recurrent stroke, rather than IL-6, C-reactive protein, or fibrinogen in particular.

Background and Purpose: The purpose of this study was to identify novel risk factors for intracerebral hemorrhagic stroke (ICH)., Methods: Risk factors were assessed at baseline in a pooled cohort of the Atherosclerosis Risk in Communities Study (ARIC) and the Cardiovascular Health Study (CHS) involving 21,680 adults aged 45 or over. Over 263,489 person-years of follow-up, we identified 135 incident ICH events., Results: In multivariable models, for each SD higher baseline level of fibrinogen, the relative rate of incident ICH increased 35% (95% CI, 17% to 55%). Fibrinogen was more strongly related to ICH in ARIC than in CHS. In multivariable models, those with von Willebrand factor levels above the median were 1.72 (95% CI, 0.97 to 3.03) times more likely to have an incident ICH as those below the median. Factor VIII was significantly positively related to ICH in ARIC (relative rate per standard deviation of 1.31; 95% CI, 1.07 to 1.62), but not in CHS. There was no relation in multivariable models between lipoprotein (a), Factor VII, white blood cell count, or C-reactive protein and ICH., Conclusions: Greater plasma fibrinogen and, to some degree, von Willebrand factor were associated with increased rates of ICH in these prospective studies, whereas Factor VIII was related to ICH in younger ARIC study participants only.

Background and Purpose: An abnormal expression of some matrix metalloproteinases (MMPs) is related with hemorrhagic transformation events after stroke. Our aim was to investigate MMP-2 and MMP-9 in the ischemic brain and its relation with blood-brain barrier breakdown after hemorrhagic transformation in human stroke., Methods: We assessed 5 cases of fatal ischemic strokes with hemorrhagic complications; brain samples were obtained from infarct, hemorrhagic, and contralateral tissue. MMP-9 and MMP-2 content was analyzed by zymography and immunohistochemistry was performed to localize MMP-9 and to assess collagen IV integrity in the basal lamina. Laser capture microdissection was performed to isolate blood-brain barrier vessels to study these MMPs., Results: Overall, MMP-9 levels were higher both in hemorrhagic and nonhemorrhagic infarcted tissue compared to contralateral areas (P<0.0001 and P<0.05). Moreover, levels of the cleaved MMP-9 85kDa-form were significantly elevated in the hemorrhagic compared to nonhemorrhagic and contralateral areas (P=0.033 and P<0.0001). No changes were found for MMP-2 content. Immunostaining revealed a strong MMP-9-positive neutrophil infiltration surrounding brain microvessels associated with severe basal lamina type IV collagen degradation and blood extravasation. Microdissection confirmed that content of MMP-9 was similarly high in microvessel endothelium from hemorrhagic and infarcted areas compared to contralateral hemisphere vessels (P<0.05), pointing to neutrophils surrounding dissected microvessels as the main source of MMP-9 in hemorrhagic areas., Conclusions: Our results show a strong neutrophil infiltration in the infarcted and hemorrhagic areas with local high MMP-9 content closely related to basal lamina collagen IV degradation and blood-brain barrier breakdown. Microvessel and inflammatory MMP-9 response are associated with hemorrhagic complications after stroke.

Background and Purpose: Inflammatory and immune mechanisms can precipitate cerebrovascular thrombosis and hemorrhage. Immunologic tolerance can be induced to a specific antigen by intranasal instillation of that antigen. Lymphocytes tolerized in this way provide local immunosuppression on restimulation with the same antigen. This study tests whether tolerization of lymphocytes to E-selectin can suppress local vessel activation and prevent stroke., Methods: Spontaneously hypertensive genetically stroke-prone rats (n=113) were distributed among the following studies: comparison of ischemic infarcts/intraparenchymal hemorrhages after single or repetitive tolerization schedules with ovalbumin, E-selectin, or PBS; comparison of E-selectin tolerization- and PBS tolerization-induced suppression of delayed-type hypersensitivity in animals subsequently sensitized to E-selectin; and comparison of PBS-, ovalbumin-, and E-selectin-tolerized groups (after intravenous lipopolysaccharide to activate vessels) regarding transforming growth factor-beta1-positive splenocyte counts, plasma interferon-gamma levels, anti-human E-selectin antibodies, endothelial intercellular adhesion molecule-1, and anti-endothelial cell antibodies., Results: Nasal instillation of E-selectin, which is specifically expressed on activated endothelium, potently inhibited the development of ischemic and hemorrhagic strokes in spontaneously hypertensive stroke-prone rats with untreated hypertension. Repeated schedules of tolerization were required to maintain the resistance to stroke. Suppression of delayed-type hypersensitivity to E-selectin and increased numbers of transforming growth factor-beta1-positive splenocytes showed that intranasal exposure to E-selectin induced immunologic tolerance. E-selectin tolerization also reduced endothelial activation and immune responses after intravenous lipopolysaccharide, as shown by marked suppression of intercellular adhesion molecule-1 expression, anti-endothelial cell antibodies on luminal endothelium, and plasma interferon-gamma levels compared with the control condition., Conclusions: The novel findings in this study support further investigation of immunologic tolerance as applied to the prevention of stroke.

Background and Purpose: Intracerebral hemorrhage is associated with stroke and head trauma. The purposes of this study were to investigate the effect of intracortical injections of autologous whole blood and blood components on inflammatory cell infiltration and brain cell death and to determine if nonhemorrhagic lesions differ in these respects., Methods: Eighty-seven adult rats were subjected to intracortical injections of autologous whole blood or allogeneic plasma, erythrocytes, leukocytes, "activated" leukocytes, and serum. Injections of saline or mineral oil were controls. Blood injections were compared with cortical freeze injury and pial devascularization. Rats were perfusion-fixed 48 hours after injection or lesioning. Eosinophilic neurons, TUNEL-positive cells, brain damage area, infiltrating neutrophils, and CD8a-immunoreactive lymphocytes were quantified., Results: Damage area, dying cells, and inflammatory infiltrate were significantly greater after autologous whole blood, leukocyte, and "activated" leukocyte injections than injection of other fractions., Conclusions: These results suggest that extravasated whole blood causes a greater degree of cortical cell death and inflammation than ischemic lesions of similar size. Leukocytes "activated" by systemic illness might exacerbate the injury. Secondary hemorrhagic phenomena suggest that the harmful effect is directed toward both brain cells and the vasculature. Further studies are required to delineate the mechanism(s).

Background and Purpose: The aims of this prospective and multicenter study were to determine the frequency of anticardiolipin and antinuclear antibodies in an unselected ischemic and hemorrhagic stroke population and to evaluate the clinical significance of these autoantibodies., Methods: Over a 1-year period, we collected plasma from 481 consecutive patients with ischemic or hemorrhagic stroke attending four different hospitals. Blood (10 mL) was drawn from each subject into a citrated glass tube. Plasma was obtained immediately by centrifugation and was stored at -70 degrees C until use. Concentrations of IgM and IgG anticardiolipin antibodies were measured at room temperature in normal (not heat-treated) plasma by standardized enzyme-linked immunosorbent assay. All sera were treated by indirect immunofluorescence on mouse liver and kidney sections for antinuclear antibodies., Results: A total of 481 patients (325 men, 156 women) 16 to 90 years in age (mean age, 61 years) were studied. Anticardiolipin antibodies were present in 5 of 481 (1.04%) patients. One patient was IgG positive and four patients were IgM positive. Of 481 patients, 35 (7.2%) were positive for antinuclear antibodies. Anti-DNA antibodies were not demonstrable in any patient., Conclusions: The frequency of anticardiolipin antibodies in a heterogeneous stroke population is possibly lower than reported. The routine screening of anticardiolipin and antinuclear antibodies in a stroke population is of questionable value.