Cytokines-Def

是由免疫原或其他因子刺激免疫细胞和其他细胞所产生并分泌的低分子量可溶性蛋白质,具有多种调控机体免疫和非免疫系统发育与功能的作用。

Cytokines are proteins that are secreted by cells and transduce signals via specific cell surface receptors on either the cytokine-producing cell (autocrine actions) or on other target cells (paracrine actions).

autocrine/paracrine actions
From this operational type of description, it is clear that the distinction between cytokines, growth factors, and hormones may be imprecise. In general, cytokines and growth factors are similar, except that the term “cytokine” most often refers to molecules involved in host defense that have actions on leukocytes, whereas the term “growth factor” more often refers to molecules acting on other somatic cell types.
on leukocytes