Importance of T Lymphocytes in Brain Injury, Immunodeficiency, and Recovery after Cerebral Ischemia

Abstract

Following an ischemic stroke, T lymphocytes become activated, infiltrate the brain, and appear to release cytokines and reactive oxygen species to contribute to early inflammation and brain injury. However, some subsets of T lymphocytes may be beneficial even in the early stages after a stroke, and recent evidence suggests that T lymphocytes can also contribute to the repair and regeneration of the brain at later stages. In the hours to days after stroke, T-lymphocyte numbers are then reduced in the blood and in secondary lymphoid organs as part of a 'stroke-induced immunodeficiency syndrome,' which is mediated by hyperactivity of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, resulting in increased risk of infectious complications. Whether or not poststroke T-lymphocyte activation occurs via an antigenindependent process, as opposed to a classical antigen-dependent process, is still controversial. Although considerable recent progress has been made, a better understanding of the roles of the different T-lymphocyte subpopulations and their temporal profile of damage versus repair will help to clarify whether T-lymphocyte targeting may be a viable poststroke therapy for clinical use.

Immune Cell Infiltration in Malignant Middle Cerebral Artery Infarction: Comparison with Transient Cerebral Ischemia

“…13,18 It has been assumed that the process of postischemic brain inflammation is facilitated by reperfusion but is limited in the absence of reperfusion. Our study has examined the profile of immune cell infiltration at early time points after pMCAO in mice, a model of human MCA infarction lacking cerebral reperfusion.…”

“…11,12 Further, T lymphocytes are now understood to contribute to ischemic brain injury after reperfusion. 13,14 Thus, Rag1 À / À mice that are deficient in lymphocytes appear to be partially protected from severe histochemical and functional outcomes after cerebral ischemia and reperfusion due to the absence of T lymphocytes. 15 By contrast, other infiltrating cells such as regulatory B cells may act to limit severity of stroke outcome after transient cerebral ischemia.…”

Immunopathogenetic Aspects of Ischemic Stroke

“…Необходимое для функционального восстановления создание новой нейральной сети достигается за счет акти-вации нейрогенеза, нейропластичности, синап-тогенеза, ангиогенеза и глиогенеза. Предпола-гается, что Т-клетки, вовлеченные в иммунный ответ, участвуют в запуске и продвижении этих репаративных механизмов преимущественно за счет продукции нейротрофических и регуля-торных факторов [9]. Действительно, Т-клетки принимают участие в поддержании нейрогенеза в гипокампе [131].…”

Inflammatory Biomarker and Stroke Rehabilitation a New Point of View about the Role in Prognostic Factor

“…Several studies have seen that an attenuation of the inflammatory process could be a possible way to widen the therapeutic window after the acute event [8,11,12]. However, other studies pointed out that the inflammatory response is necessary in order, for example, to remove dead neurons and other brain cells in the ischaemic core, and promote astrocytosis.…”

“…Recent studies have shown that T-cells also have an impact on tissue damage [12][13][14][15][16][17][18][19][20]. Several studies have seen that an attenuation of the inflammatory process could be a possible way to widen the therapeutic window after the acute event [8,11,12].…”