Horowitz M C, Friedlaender G E, Qian H Y
Department of Orthopaedics and Rehabilitation, Yale University, School of Medicine, New Haven, CT 06520-8071, USA.
Clin Orthop Relat Res. 1996 May(326):25-34. doi: 10.1097/00003086-199605000-00004.
Once naive T cells encounter antigen, they become primed effector cells. The scope of effector functions mediated by these cells defines the efferent arm of the immune response. The change from naive to primed effector cell is known as adaptive immunity and takes 2 forms: cell mediated, in which T cells mediate effector function, and humoral, in which antibodies are the effector molecules. There are 3 types of effector T cells: inflammatory CD4 T cells, which activate macrophages; helper CD4 T cells, which help B lymphocytes produce antibody; and cytotoxic CD8 T cells, which kill their target cells. The interaction of primed effector cells with their targets results in phenotypic changes in the cells and the secretion of cytokines. These cytokines may be secreted by the primed effector T cell, the target cell, or both. Cytokines function in either autocrine (secreted and used by the same cell) or paracrine (secreted by 1 cell and used by a different cell) circuits and have marked regulatory effects on cells in both the immune and skeletal systems. Many of these cytokines, which were once thought to be products exclusively of immune cells, are now known to be produced by cells of the skeletal system. Both the specific and nonspecific components of the immune response have profound effects on remodeling of the musculoskeletal system during normal and pathologic states.
一旦初始T细胞遇到抗原，它们就会转变为致敏效应细胞。这些细胞介导的效应功能范围定义了免疫反应的传出臂。从初始细胞到致敏效应细胞的转变被称为适应性免疫，有两种形式：细胞介导的，其中T细胞介导效应功能；体液免疫的，其中抗体是效应分子。有三种类型的效应T细胞：激活巨噬细胞的炎性CD4 T细胞；帮助B淋巴细胞产生抗体的辅助性CD4 T细胞；以及杀死靶细胞的细胞毒性CD8 T细胞。致敏效应细胞与其靶细胞的相互作用导致细胞表型变化和细胞因子的分泌。这些细胞因子可能由致敏效应T细胞、靶细胞或两者分泌。细胞因子在自分泌（由同一细胞分泌并作用于自身）或旁分泌（由一个细胞分泌并作用于另一个细胞）途径中发挥作用，对免疫系统和骨骼系统中的细胞都有显著的调节作用。许多这些曾经被认为是免疫细胞特有的产物的细胞因子，现在已知也由骨骼系统的细胞产生。免疫反应的特异性和非特异性成分在正常和病理状态下对肌肉骨骼系统的重塑都有深远影响。
