Patel Sangita P, Dana Reza
Cornea and Refractive Surgery Services, Massachusetts Eye and Ear Infirmary, Harvard Medical School, 243 Charles St., Boston, MA 02114, USA.
Semin Ophthalmol. 2009 May-Jun;24(3):135-8. doi: 10.1080/08820530902801320.
The lymphatic system is a network of vessels throughout the body that serves to return lymphatic fluid to the systemic blood circulation and serves as the immune system's highway in the afferent limb of the immune response. This paper reviews the basics of structure, function and development of the lymphatic system. The emphasis is on understanding the role of lymphatics in the cornea as related to angiogenesis and the clinical setting of corneal transplant rejection. The lymphatic system has two main functions: to drain excess extracellular fluid from capillary beds to return to the systemic blood circulation and to capture antigen for presentation to the immune system in the lymphoid compartment (e.g. nodes) connected in parallel to the lymphatic system. The normal cornea is devoid of lymphatic vessels and blood vessels, thus allowing for its unique immune privileged status. Abnormal blood vessel growth into the cornea has been studied for many years, but the study of lymphatic vessels has been hampered until the recent discovery of lymphatic-specific markers. Subsequent studies of vascularized corneas support the presence of lymphatic vessels in the cornea. The growth of new lymphatic (lymphangiogenesis) and blood (hemangiogenesis) vessels in the cornea is closely related to the abrogation of the immune privileged status of the cornea. This review summarizes our current understanding of the parallel development of hemangiogenesis and lymphangiogenesis as related to the mechanisms of immune rejection of corneal transplants.
淋巴系统是遍布全身的血管网络，其作用是将淋巴液回流至体循环，并且在免疫反应的传入环节中充当免疫系统的通道。本文综述了淋巴系统的结构、功能及发育的基础知识。重点在于理解淋巴管在角膜中与血管生成及角膜移植排斥临床情况相关的作用。淋巴系统有两个主要功能：从毛细血管床引流多余的细胞外液，以回流至体循环；捕获抗原，呈递给与淋巴系统平行连接的淋巴组织（如淋巴结）中的免疫系统。正常角膜没有淋巴管和血管，因此具有独特的免疫赦免状态。角膜异常血管生成已被研究多年，但直到最近发现淋巴管特异性标志物，淋巴管的研究才受到阻碍。随后对血管化角膜的研究证实了角膜中存在淋巴管。角膜中新的淋巴管生成（淋巴管生成）和血管生成（血管生成）与角膜免疫赦免状态的消除密切相关。本综述总结了我们目前对与角膜移植免疫排斥机制相关的血管生成和淋巴管生成平行发展的理解。
