New Concept of Antigen Presentation by Gingival Epithelial Cells in Periodontal Disease.

本研究的目的是阐明牙周疾病中牙龈上皮细胞提呈抗原的新概念。主要组织相容性复合体(MHC)II类分子在牙周病患者牙周组织中主要由上皮细胞表达，而在正常牙周组织中不表达。共聚焦显微镜分析显示，牙周病组织中的牙龈上皮细胞(GEC)同时表达人类白细胞抗原DR和B7-1(CD80)共刺激分子。建立大鼠肾小管上皮细胞系，探讨其对MHC-II和B7-1表达的可能作用。用干扰素-γ刺激大鼠肾小管上皮细胞系可诱导MHC-II类分子的表达，而逆转录-聚合酶链式反应和流式细胞术检测到B7-1共刺激分子的表达。伴放线放线杆菌Omp29特异性CD4Th1克隆细胞在固定化放线菌伴生放线杆菌和干扰素-γ预刺激下增殖。然而，单用细菌或单用干扰素-γ处理GEC后，Th1细胞不产生反应。抗MHCⅡ类抗体或CTLA4免疫球蛋白(CTLA4-Ig)可抑制GEC诱导的Th1克隆细胞的活化。虽然淋巴T细胞和Th1克隆细胞对葡萄球菌肠毒素A的超抗原活性敏感，但淋巴T细胞对伴生放线杆菌没有表现出超抗原活性，而在干扰素-γ处理的GEC中培养的T细胞对超抗原活性敏感。这些结果表明，GEC可以结合细菌抗原，进而通过MHC-II结合B7共刺激作用将细菌抗原处理并呈递给CD4^+T细胞。GEC似乎通过刺激抗原特异性的CD4^+T细胞在获得性免疫反应中发挥作用。

The purpose of the present research project was to clarify the new concept of antigen presentation by gingival epithelial cells in periodontal disease. HLA-DR (major histocompatibility complex [MHC] class II) is often expressed by epithelial cells in gingival tissues with periodontal disease but not by cells in healthy gingival tissues. Confocal microscopic analyses revealed that gingival epithelial cells(GEC) from tissue with periodontal disease express both HLA-DR and B7-1(CD80) costimulatory molecules. Rat GEC lines were established to elucidate the possible role of MHC class II and B7-1 expression by GEC. Stimulation of a rat GEC line with gamma interferon (IFN-γ) induced the expression of MHC class II, whereas the cell line constitutively expressed B7-1 costimulatory molecules as determined by reverse transcription-PCR and flow cytometry. Actinobacillus actinomycetemcomitans Omp29-specific CD4^+ Th1 clone cells proliferated in response to pretreatment of GEC with fixed A.actinomycetemcomitans and IFN-γ. However, the Th1 cells did not respond to pretreatment of GEC with the bacteria alone or IFN-γalone. The activation of Th1 clone cells induced by the GEC was inhibited by antibody to MHC class II or by CTLA4 immunoglobulin(CTLA4-Ig). Lymph node T cells did not demonstrate superantigen activity to A.actinomycetemcomitans, although both lymph node T cells and Th1 clone cells were sensitive to superantigen activity of staphylococcal enterotoxin A as cultured in the presence of IFN-γ-treated GEC. These results suggested that GEC can take up bacterial antigen and consequently process and present the bacterial antigen to CD4^+ T cells by MHC class II in conjunction with B7 costimulation. GEC appeared to play a role in the adaptive immune response by stimulating antigen-specific CD4^+ T cells.