Stress responses are part of an important system in maintaining the homeostasis of a living organism. After acute inflammation, if tissue repair is incomplete or stress is not completely removed with an excessive and prolonged inflammatory response, damage is accumulated in living organs and chronic inflammation persists. Thus, irreversible tissue and organ damage occurs, which is accompanied by fibrosis. Further, inflammatory diseases, such as fibrotic diseases, autoimmune diseases, allergies, and arteriosclerosis, account for most causes of deaths in humans; therefore, it is extremely important to understand mechanisms of inflammation and to establish a control method. Inflammation is caused by a complex influence of various molecules and cells that form networks through inflammatory cytokines. Since various factors influence each other, the onset time, degree, and duration of inflammation may differ. This article explains the mechanism of inflammation, presents findings on its regulatory factors and methods, and enumerates the innate immune system receptors (pattern recognition receptors) and responsible cells (neutrophils, innate lymphoid cells, natural killer T cells) that cause inflammation. This article thus aims to understand the complex networks involved in inflammation.
