Peyssonaux Carole, Johnson Randall S
Division of Biological Sciences, University of California, San Diego, San Diego, California 92093-0366, USA.
Cell Cycle. 2004 Feb;3(2):168-71.
The eradication of invading microorganisms depends initially on innate immunity mechanisms that preexist in all individuals and act within minutes of infection. Pathogen spread is often countered by an inflammatory response that recruits more effector molecules and cells of the innate immune system from local blood vessels, while inducing clotting farther downstream so that pathogens cannot spread throughout the blood. If a microorganism crosses an epithelial barrier and begins to replicate in the tissues of the host, it is, in some cases, immediately recognized by the mononuclear phagocytes, or macrophages, that reside in tissues. Macrophages mature continuously from circulating monocytes that leave the circulation to migrate into tissues throughout the body. The second major family of phagocytes, the neutrophils or polymorphonuclear leukocytes (PMNs) are short-lived cells that are abundant cells in the blood but are not present in healthy tissues. Both phagocytic cell types play a key role in innate immunity because they can recognize, ingest and destroy many pathogens without the aid of an adaptive immune response. This infiltration of neutrophils and later macrophages to the site of bacterial infection is tightly linked with the need of these immune defense cells to respond to the tissue microenvironment.
入侵微生物的根除最初依赖于先天性免疫机制，这种机制存在于所有个体中，并在感染后几分钟内发挥作用。病原体的传播通常会引发炎症反应，该反应会从局部血管招募更多先天性免疫系统的效应分子和细胞，同时在更下游诱导凝血，从而使病原体无法在血液中扩散。如果微生物穿过上皮屏障并开始在宿主组织中复制，在某些情况下，它会立即被驻留在组织中的单核吞噬细胞或巨噬细胞识别。巨噬细胞由循环中的单核细胞不断成熟而来，这些单核细胞离开循环系统，迁移到全身组织中。吞噬细胞的第二个主要类别，即中性粒细胞或多形核白细胞（PMN），是寿命较短的细胞，它们在血液中数量丰富，但在健康组织中不存在。这两种吞噬细胞类型在先天性免疫中都起着关键作用，因为它们无需适应性免疫反应的帮助就能识别、摄取和破坏许多病原体。中性粒细胞以及随后巨噬细胞向细菌感染部位的浸润与这些免疫防御细胞对组织微环境作出反应的需求紧密相关。
