Early detrimental T-cell effects in experimental cerebral ischemia are neither related to adaptive immunity nor thrombus formation

Abstract

AbstractT cells contribute to the pathophysiology of ischemic stroke by yet unknown mechanisms. Mice with transgenic T-cell receptors (TCRs) and mutations in costimulatory molecules were used to define the minimal immunologic requirements for T cell–mediated ischemic brain damage. Stroke was induced in recombination activating gene 1–deficient (RAG1−/−) mice devoid of T and B cells, RAG1−/− mice reconstituted with B cells or T cells, TCR-transgenic mice bearing 1 single CD8+ (2C/RAG2, OTI/RAG1 mice) or CD4+ (OTII/RAG1, 2D2/RAG1 mice) TCR, mice lacking accessory molecules of TCR stimulation (CD28−/−, PD1−/−, B7-H1−/− mice), or mice deficient in nonclassical T cells (natural killer T [NKT] and γδ T cells) by transient middle cerebral artery occlusion (tMCAO). Stroke outcome was assessed at day 1. RAG1−/− mice and RAG1−/− mice reconstituted with B cells developed significantly smaller brain infarctions compared with controls, but thrombus formation after FeCl3-induced vessel injury was unimpaired. In contrast, TCR-transgenic mice and mice lacking costimulatory TCR signals were fully susceptible to tMCAO similar to mice lacking NKT and γδ T cells. These findings were corroborated by adoptive transfer experiments. Our data demonstrate that T cells critically contribute to cerebral ischemia, but their detrimental effect neither depends on antigen recognition nor TCR costimulation or thrombus formation.