Chodosh J, Nordquist R E, Kennedy R C
Department of Ophthalmology, Dean A. McGee Eye Institute, Oklahoma City, USA.
Adv Exp Med Biol. 1998;438:557-65. doi: 10.1007/978-1-4615-5359-5_79.
Ocular surface immune mechanisms are subservient to the fine function of the eye. A clear cornea with a smooth, well-lubricated facade is prerequisite to lucid vision. Hence, corneal inflammation and post-inflammatory scarring are intolerable, and the cornea contains a minimum of lymphoid elements. Although conjunctival dysfunction and consequent tear film deficiency can malign the corneal surface, conjunctival inflammation is tolerated to a considerable degree. In contrast to the human cornea, human conjunctiva contains an abundance of lymphoid tissue. Certain aspects of human conjunctival immunology elicit little debate. Langerhans cells are abundant in conjunctival epithelium. Isolated CD8+ suppressor/cytotoxic T cells predominate in conjunctival epithelium, while T cells in the substantia propria distribute equally between CD4+ T helper cells and CD8+ cells. Yet the presence of plasma cells in human conjunctiva, the expression of secretory component by human conjunctival epithelium, and the function of human conjunctival lymphoid follicles are in dispute. Confusion may derive in part from the use of inappropriate animal models; rodent conjunctiva does not appear to be a worthy facsimile for human conjunctiva. Discrepancies between different human studies likely result from variance in subject age, biopsy site and extent, histologic or histochemical technique, and perhaps the degree of inflammation present at the time of biopsy. Careful immunohistochemical and in situ molecular assays on well-defined loci within the conjunctiva of comparable human subjects may resolve such questions in the future. Organized mucosa-associated lymphoid tissue is rigorously defined as mucosal lymphoid follicles with an ultrastructurally distinct overlying lymphoepithelium. Based on available evidence, the epithelium overlying mammalian conjunctival lymphoid follicles does not contain distinct M cells. Whether zonal differences in morphology reflect real differences in the capacity to sample tear film antigens for presentation to the mucosal immune system remains to be established.
眼表免疫机制服从于眼睛的精细功能。具有光滑、润滑良好外观的透明角膜是清晰视力的先决条件。因此，角膜炎症和炎症后瘢痕形成是无法容忍的，且角膜含有最少的淋巴样成分。尽管结膜功能障碍及随之而来的泪膜缺乏会损害角膜表面，但结膜炎症在很大程度上是可以耐受的。与人类角膜不同，人类结膜含有丰富的淋巴组织。人类结膜免疫学的某些方面几乎没有争议。朗格汉斯细胞在结膜上皮中大量存在。孤立的CD8 +抑制/细胞毒性T细胞在结膜上皮中占主导地位，而固有层中的T细胞在CD4 +辅助性T细胞和CD8 +细胞之间平均分布。然而，人类结膜中浆细胞的存在、人类结膜上皮分泌成分的表达以及人类结膜淋巴滤泡的功能仍存在争议。部分混淆可能源于使用了不恰当的动物模型；啮齿动物结膜似乎并非人类结膜的合适模拟物。不同人类研究之间的差异可能源于受试者年龄、活检部位和范围、组织学或组织化学技术的差异，或许还源于活检时存在的炎症程度。未来，对可比人类受试者结膜内明确位点进行仔细的免疫组织化学和原位分子检测可能会解决此类问题。有组织的黏膜相关淋巴组织被严格定义为具有超微结构上独特的覆盖淋巴上皮的黏膜淋巴滤泡。根据现有证据，覆盖哺乳动物结膜淋巴滤泡的上皮不包含明显的M细胞。形态学上的区域差异是否反映了在摄取泪膜抗原以呈递给黏膜免疫系统的能力方面的实际差异仍有待确定。
