The Spectrum of Systemic Immune Alterations After Murine Focal Ischemia

Abstract

Background and Purpose-Therapeutic modification of the postischemic immune processes is a key target of current experimental stroke research. For successful translation into the clinical setting, experimental studies must account for the impact of different strokes on the immune system including susceptibility to infection. Herein, we characterize the impact of 3 ischemia models on systemic immunological and microbiological parameters. Methods-In C57Bl/6 mice (nϭ235), the middle cerebral artery was occluded (MCAO) either permanently by distal coagulation or transiently by an intraluminal filament for 30 minutes or 90 minutes. Differential leukocyte counts were performed in blood and lymphatic organs. Lymphocyte subpopulations and apoptotic cells were characterized by flow cytometry. Blood cytokine concentrations were measured by ELISA. Microbiological cultures were grown from blood and lung samples. Results-Only extensive infarcts induced leukopenia 24 hours, 3 days and 7 days after MCAO and decreased lymphocyte counts in spleen, lymph nodes and thymus. In contrast, small infarcts led to no significant changes in differential blood count or reduction of overall cell counts in lymphatic organs. Splenic lymphocyte apoptosis and blood cytokine production was significantly increased after extensive lesions compared to mild ischemia. Hypothermia and weight loss occurred only in mice with large infarcts which also suffered from pneumonia and sepsis. In contrast to infarct size, location and side of the infarct did not affect physiological parameters and immune cell alterations. Conclusions-Postischemic systemic immunomodulation and infectious complications differ substantially among stroke models. Translational studies of immunomodulatory therapies for stroke must account for this heterogeneity.

Amplification of Regulatory T Cells Using a CD28 Superagonist Reduces Brain Damage After Ischemic Stroke in Mice

“…The mortality in this model was 5% in both groups. In accordance with previous reports, 26 we observed a significantly decreased absolute cell number of total CD4+CD3+ T cells in the spleen in both CD28SA-and isotype-treated control mice 3 days after MCAO in this stroke model, which causes substantially larger infarcts ( Figure 3A and 3B). However, after CD28SA treatment, absolute Foxp3+ Treg splenic cell counts as well as their percentage within the CD4+ T cell population were significantly increased compared with the control group ( Figure 3A and 3B).…”

Regulatory T cells are strong promoters of acute ischemic stroke in mice by inducing dysfunction of the cerebral microvasculature

“…Moreover, the extent of brain damage (large infarctions vs small infarctions) might have differentially influenced the function of Tregs and, therefore, stroke outcome. [41][42][43] Finally, Liesz et al predominantly focused on the contribution of Tregs for tissue reorganization and repair at later stages of infarct development, 7 whereas our study above all was intended to analyze the acute effects of Tregs in stroke pathogenesis. 44 and diphtheria toxin injection did not lead to a loss of epithelial integrity in the DEREG model, making the "nonimmune" effects of diphtheria toxin treatment in the tMCAO model unlikely.…”

Modeling Stroke in Mice - Middle Cerebral Artery Occlusion with the Filament Model

“…6,33,34 The use of environmental enrichment and its effect on reproducibility is a matter of discussion. 35 Another important confounder is the stroke induced risk for infection especially after longer times of ischaemia 36 , which leads to additional morbidity and increased mortality. 37,38 As infections become symptomatic at around day 3 to 5, this has important consequences for long term follow-up in such models.…”