Innate Immunity Laboratory, Institute of Experimental Medicine (IMEX), National Academy of Medicine/CONICET, Buenos Aires, Argentina.
Department of Ophthalmology, Ocular Surface Center, Cullen Eye Institute, Baylor College of Medicine, Houston, TX, USA.
Immunology. 2021 Sep;164(1):43-56. doi: 10.1111/imm.13338. Epub 2021 May 2.
The ocular surface is the part of the visual system directly exposed to the environment, and it comprises the cornea, the first refractive tissue layer and its surrounding structures. The ocular surface has evolved to keep the cornea smooth and wet, a prerequisite for proper sight, and also protected. To this aim, the ocular surface is a bona fide mucosal niche with an immune system capable of fighting against dangerous pathogens. However, due to the potential harmful effects of uncontrolled inflammation, the ocular surface has several mechanisms to keep the immune response in check. Specifically, the ocular surface is maintained inflammation-free and functional by a particular form of peripheral tolerance known as mucosal tolerance, markedly different from the immune privilege of intraocular structures. Remarkably, conjunctival tolerance is akin to the oral and respiratory tolerance mechanisms found in the gut and airways, respectively. And also similarly, this form of immunoregulation in the eye is affected by ageing just as it is in the digestive and respiratory tracts. With ageing comes an increased prevalence of immune-based ocular surface disorders, which could be related to an age-related impairment of conjunctival tolerance. The purpose of this review was to summarize the present knowledge of ocular mucosal tolerance and how it is affected by the ageing process in the light of the current literature on mucosal immunoregulation of the gut and airways.
眼球表面是视觉系统中直接暴露于环境的部分，它包括角膜、第一折射组织层及其周围结构。眼球表面已经进化到保持角膜光滑和湿润的程度，这是正常视力的前提，也是受保护的。为此，眼球表面是一个真正的黏膜龛，拥有能够对抗危险病原体的免疫系统。然而，由于不受控制的炎症可能产生潜在的有害影响，眼球表面有几种机制来控制免疫反应。具体来说，通过一种称为黏膜耐受性的特殊形式的外周耐受，眼球表面保持无炎症和功能性，这与眼内结构的免疫特权明显不同。值得注意的是，结膜耐受性类似于在肠道和气道中发现的口腔和呼吸道耐受性机制。同样，这种在眼睛中的免疫调节形式也像在消化道和呼吸道中一样受到衰老的影响。随着年龄的增长，以免疫为基础的眼球表面疾病的患病率增加，这可能与结膜耐受性的年龄相关损害有关。本综述的目的是根据目前关于肠道和气道黏膜免疫调节的文献，总结眼球黏膜耐受性的现有知识及其如何受到衰老过程的影响。
