One of the main functions of mitochondria is production of ATP for cellular energy needs, however, it becomes more recognized that mitochondria are involved in differentiation and activation processes of immune cells. Upon activation, immune cells have a high need for energy. Immune cells have different strategies to generate this energy. In pro-inflammatory cells, such as activated monocytes and activated T and B cells, the energy is generated by increasing glycolysis, while in regulatory cells, such as regulatory T cells or M2 macrophages, energy is generated by increasing mitochondrial function and beta-oxidation.

Except for being important for energy supply during activation, mitochondria also induce immune responses. During an infection, they release mitochondrial danger associated molecules (DAMPs) that resemble structures of bacterial derived pathogen associated molecular patterns (PAMPs). Such mitochondrial DAMPS are for instance mitochondrial DNA with hypomethylated CpG motifs or a specific lipid that is only present in prokaryotic bacteria and mitochondria, i.e. cardiolipin. Via release of such DAMPs, mitochondria guide the immune response towards an inflammatory response against pathogens. This is an important mechanism in early detection of an infection and in stimulating and sustaining immune responses to fight infections. However, mitochondrial DAMPs may also have a negative impact. If mitochondrial DAMPs are released by damaged cells, without the presence of an infection, such as after a trauma, mitochondrial DAMPs may induce an undesired inflammatory response, resulting in tissue damage and organ dysfunction. Thus, immune cells have developed mechanisms to prevent such undesired immune activation by mitochondrial components.

In the present narrative review, we will describe the current view of mitochondria in regulation of immune responses. We will also discuss the current knowledge on disturbed mitochondrial function in immune cells in various immunological diseases.

线粒体的主要功能之一是满足细胞能量需求的ATP产生，但是，人们越来越认识到，线粒体参与了免疫细胞的分化和激活过程。激活后，免疫细胞对能量的需求很高。免疫细胞具有产生这种能量的不同策略。在促炎性细胞（如活化的单核细胞以及活化的T和B细胞）中，能量是通过增加糖酵解产生的；而在调节性细胞（如调节性T细胞或M2巨噬细胞）中，能量是通过增加线粒体功能和β-氧化产生的。

线粒体除了对激活过程中的能量供应很重要以外，还可以诱导免疫反应。在感染期间，它们释放线粒体危险相关分子（DAMP），其类似于细菌衍生的病原体相关分子模式（PAMP）的结构。这种线粒体DAMPS是例如具有低甲基化的CpG基序的线粒体DNA或仅存在于原核细菌和线粒体中的特定脂质，即心磷脂。线粒体通过释放这种DAMP来引导免疫反应朝着针对病原体的炎症反应。这是早期发现感染以及刺激和维持抵抗感染的免疫反应的重要机制。但是，线粒体DAMPs也可能产生负面影响。如果线粒体DAMP被受损细胞释放，在没有感染的情况下（例如在创伤后），线粒体DAMPs可能会引起不良的炎症反应，从而导致组织损伤和器官功能障碍。因此，免疫细胞已开发出防止这种不希望的线粒体免疫活化的机制。

在目前的叙述性综述中，我们将描述线粒体在调节免疫反应中的当前观点。我们还将讨论有关各种免疫疾病中免疫细胞线粒体功能紊乱的最新知识。