Pneumonia is one of the most common complications for patients with stroke. Recently, more and more attention has been paid on the roles of immune system in pneumonia and immunosuppression after stroke has been regarded as an independent risk factor for infections. Experimental and clinical studies have identified a series of inflammation and immunosuppression after stroke, including the reduction of mononuclear phagocyte and natural killer cell function, induction of anti-inflammatory cytokines, apoptosis of lymphocyte and alteration of T lymphocyte activity. The mechanism is likely to be that immunosuppressive signals impact on the nervous system through the hypothalamus-pituitary adrenal axis, sympathetic adrenergic axis, and the parasympathetic adrenergic axis, which lead to the changes of immune system and down-regulation of immune function as well. In addition, some other studies attested that stroke-induced immunosuppression had protective effect on the brain. The mechanism regarding immunosuppression remains unclear now but do exist. Obviously, the further research on the stroke-induced immunosuppression will have great significance on the prevention of pneumonia after stroke.%肺炎是脑卒中患者最常见的并发症之一.近年来,免疫系统在脑卒中后肺炎中所起的作用越来越受到重视,脑卒中后免疫抑制被认为是引起感染的独立危险因素.通过实验和临床研究发现,脑卒中后一系列炎症与免疫应答改变包括单核巨噬细胞、自然杀伤细胞的功能减低,诱导抗炎因子生成,促进淋巴细胞凋亡和T淋巴细胞的活性改变.其机制可能是免疫抑制信号通过下丘脑-垂体-肾上腺轴、交感肾上腺素轴和副交感神经系统3种途径作用于免疫系统,导致免疫系统发生改变,免疫功能下调.也有实验证明,脑卒中后免疫抑制具有脑保护作用.脑卒中后免疫抑制客观存在,其机制仍不清楚.对脑卒中后免疫抑制的进一步研究,对减少脑卒中后肺炎的发生有重大意义.
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