RESUMO
The cornea is a transparent outer layer of the anterior eye segment, innervated by a high density of neural tissue. In the process of corneal innervation, trigeminal ganglion originated corneal nerves traverse different types of corneal cell in the epithelial and stromal layers. Corneal stromal cells, epithelial cells, immune cells, and other cells interact closely to maintain corneal microenvironmental homeostasis. In addition, corneal nerves is associated with the occurrence and development of many ocular surface diseases. Corneal nerves release various active peptides that regulate corneal sensation, maintain epithelial integrity and proliferation, improve wound healing, and manage local inflammation and immune response. This article reviews the advances in the corneal nerve regulation of the ocular surface microenvironment, providing some new ideas for the further study and treatment of corneal nerve-associated diseases.
RESUMO
BACKGROUND: Cell therapy, recombinant proteins and biomacromolecule preparations have been widely used in clinical practice; however, transplant rejections caused by xenogeneic proteins limit the safe and reusable use of such macromolecules. OBJECTIVE: To review the immunocamouflage mechanism of polyethylene glycol and the current application in the modification of macromolecules or biological vectors. METHODS: The authors retrieved articles about the immune camouflage of polyethylene glycol in WanFang, VIP and PubMed databases by the keywords as follows: "polyethylene glycol; immunocamouflage or immune camouflage; transplantation, and rejection" in Chinese and English, respectively. RESULTS AND CONCLUSION: Polyethylene glycol produces an immune camouflage by forming a stereoscopic charge barrier. The pegylation on the cell surface inhibits the adhesion, recognition and immune pathway involved in the heterogeneous recognition, which can interfere with many aspects of the immune response. The pegylated erythrocytes, islet cells, and lymphocytes show a decrease in the immunogenicity and a prolonged survival after allogeneic or xenotransplantation. Some factors including concentration, molecular weight, modification time, pH value can affect the immune camouflage of polyethylene glycol. The anti-PEG antibody and its effects need to be further elucidated.