分泌片（SC）是多聚免疫球蛋白受体（pIgR）从细胞膜上脱落下来的片段。它既是S-IgA的重要组成部分，能够增强其稳定性，也可通过pIgR自身的水解被单独分泌到外分泌液中（被称为游离SC）。多年以来，相关研究致力于探索SC怎样保护S-IgA不被酶降解，以及SC在呼吸道和胃肠道中的免疫作用，却忽略了SC/pIgR在口腔内的自身免疫防御功能。唾液中的游离SC很可能是口腔防御系统中的重要因子，发挥着非特异性的免疫防御作用。本研究前期工作已探讨唾液S-IgA与主要致龋菌变异链球菌的相互作用，今后将重点研究SC/pIgR独特的口腔免疫功能，探索人唾液腺上皮细胞pIgR的跨细胞转运途径，寻找促进SC分泌的促效剂并在细胞水平上明确其上调表达机制，从而在SC基因敲除大鼠模型上探讨SC对口腔细菌的自身免疫防御作用。

Secretory component(SC) is a fragment divided from the cell membrane of poly-secretory immunoglobulin receptor(pIgR). It is an important part of the S-IgA, enhance the stability of S-IgA, and also can secret into the outer secretion through the hydrolysis of pIgR, which is called free SC. Over decades, relative studies devoted themselves into the functions and mechanisms of how SC protect the S-IgA from degrading by enzymes, and immune function of SC in the respiratory and gastrointestinal system, while ignoring the own immune defenses functions in the oral system of the SC/pIgR. Free SC in saliva is likely to be an important factoring oral defense system, plays an important role in non-specific immune defense. The previous research result shows the evidence of interations between S-IgA in saliva and streptococcus mutans, which is the causative agent of dental caries. This study focuses on the unique oral immune function of SC/pIgR, explore the transcellular transport pathway of PIgR from human salivary gland epithelial cells, and seek for an effect agonist to promote the secretion of SC. After clarify the mechanism of SC up-regulation by the agonist, further studies to explore the role of SC in hosts’ own immune defense against oral bacteria should be done in the SC knock-out rats model.