免疫系统包括天然免疫和适应性免疫。适应性免疫是T淋巴细胞和B淋巴细胞介导的对特定致病原或抗原的免疫反应,它的产生需要数天的时间并通过记忆T细胞和B细胞发挥作用。相比之下,天然免疫系统在感染发生的初始时刻即为宿主提供保护。以往天然免疫被认为是一种非特异性反应,表现为巨噬细胞通过内吞和消化作用清除微生物或异己抗原。近年发现一种天然识别受体——Toll样受体(Tolllikereceptors,TLRs),可通过识别特定的致病原结构来区分自身和致病原,从而启动快速的防御反应。目前研究热点主要集中在TLRs如何识别致病原、调动宿主防御反应及调节适应性免疫的作用。由于角膜天然免疫的存在,角膜虽位于眼表最 The immune system includes both innate and adaptive immunity. Adaptive immunity is an immune response mediated by T lymphocytes and B lymphocytes to a specific pathogen or antigen that takes several days to develop and functions through memory T cells and B cells. In contrast, the innate immune system provides protection to the host at the very beginning of the infection. In the past, innate immunity was considered as a nonspecific reaction, manifested as macrophages clearing microorganisms or iso-antigens by endocytosis and digestion. In recent years, a natural recognition receptor, Toll-like receptors (TLRs), has been found to recognize fasting defensive responses by recognizing specific pathogenic structures to distinguish themselves from pathogenic agents. The current research focuses on how TLRs recognize pathogenic agents, mobilize the host defense response and regulate adaptive immunity. Due to the presence of corneal innate immunity, although the cornea is located in the most ocular surface