【作者】 申龙树；

【导师】 黄培林；

【作者基本信息】 东南大学 ， 病理及病理生理， 2004， 硕士

【摘要】 机体的抗肿瘤免疫反应分为两个时相,第一时相:肿瘤的特异性抗原被抗原递呈细胞加工处理,递呈给CD4+T细胞,通过细胞因子激活静止的CD8+的T细胞成为细胞毒性T淋巴细胞(cytotoxic T lymphocyte,CTL);第二时相:激活的CTL细胞通过T细胞受体(T cell receptor,TCR)与肿瘤细胞HLA-I类分子和抗原肽复合物结合,发挥杀伤肿瘤细胞的作用。机体抗肿瘤免疫和/或肿瘤细胞逃避免疫监视的异常可能导致恶性肿瘤的发生和发展。肿瘤细胞逃避免疫反应的机制很复杂,目前研究认为其主要机制有二方面:一方面是肿瘤细胞的免疫原性低,并具有抗原调变能力,或肿瘤细胞HLA分子表达异常,使T细胞对肿瘤抗原不能识别;另外,由于宿主局部的抗原递呈细胞的数量减少和/或功能缺陷,使其无法有效递呈肿瘤抗原,激活T细胞识别和杀伤肿瘤细胞。我们从肿瘤细胞的HLA分子的表达和宿主的抗原递呈能力两个方面研究肿瘤细胞逃避机体免疫监视的机制,以期为进一步认识肿瘤免疫机理和肿瘤的免疫治疗提供理论基础。大肠癌在我国是一种常见的恶性肿瘤,随着人们生活水平的提高,该病发病率有逐年增高的趋势,严重危害人们的生存与健康。我们收集2000-2001年度东南大学附属中大医院65例大肠癌根治标本,采用免疫组化的方法(ABC法)检测大肠癌手术标本的癌组织,癌旁黏膜及切端黏膜中HLA-I、II类分子及相关抗原的表达情况,并计算大肠癌组织中免疫相关的淋巴细胞亚群和树突状细胞(Dendric cell,DC)密度,结合临床病理资料,综合分析大肠癌组织中HLA-I、II类分子的表达情况及大肠癌的局部免疫相关细胞密度,初步探讨大肠癌细胞逃避机体免疫监视的可能机制。本研究结果表明:大肠癌中的HLA-I类分子各位点重链(HLA-A、HLA-B/C)和轻链抗原(β2-microglobulin,β2m)表达显著低于其切端黏膜(P=0.001),在肠癌Dukes B,C,D期,肠癌组织中这些抗原存在异质性表达现象;肠癌组织中参与HLA-I类分子的抗原加工的低分子量蛋白2(low molecular weight protein,LMP2)、伴侣分子钙粘蛋白(Calnexin)等相关抗原较其切端黏膜及癌旁组织表达下调(P<0.05);肠癌中HLA-A、HLA-B/C、β2m各位点的表达情况<WP=5>随着大肠癌Dukes分期的递进而逐步下调,其中HLA-B/C位点表达在A期显著高于D期(P<0.05),肠癌HLA-I类分子各位点重链和β2m表达与病理分级无相关性;LMP2与肠癌分级无相关性,但随着肠癌的Dukes分期递进,LMP2表达下降;Calnexin的表达水平与肠癌分级、分期无显著相关性。65例检测的大肠癌标本中,29.23%大肠黏膜(19/65)及16.92%癌组织(11/65)表达HLA-II类分子,两者之间无显著差异,但大肠黏膜中HLA-II类分子表达强度高于大肠癌组织(P=0.001)。大肠癌组织中HLA-II类分子表达与病理的分级,分期无显著相关性,但与周围浸润的淋巴细胞密度相关(P=0.0562)。大肠癌组织与切端黏膜组织中淋巴细胞,CD8+的淋巴细胞密度分布无显著差异;随着肠癌Dukes分期递进,肠癌组织中CD8+的淋巴细胞密度逐步降低;随着肠癌分化程度降低,肠癌组织中淋巴细胞密度逐步降低。大肠癌组织中的树突状细胞的密度显著低于切端黏膜(P=0.002),与肠癌分期无关,随着肠癌的分化程度降低而逐步降低。结果提示:大肠癌细胞表面的HLA-I类分子较正常黏膜表达下调是大肠癌逃避肿瘤免疫的重要机制之一;肠癌组织中参与HLA-I类分子的抗原加工的LMP2,伴侣分子Calnexin,β2m等相关抗原表达下调是影响肠癌细胞HLA-I类分子表达的重要因素之一。DC是一种高效抗原递呈细胞,大肠癌细胞表达HLA-II类分子成为兼职抗原递呈细胞,其作用是摄取、加工、处理外源性抗原,并递呈给CD4+的T细胞,CD4+T细胞通过细胞因子激活CTL,该细胞能够特异性杀伤肿瘤细胞而发挥抗肿瘤的作用。大肠癌组织中的树突状细胞的数量显著低于切端黏膜,肠癌细胞HLA-II类分子的表达强度显著低于切端黏膜组织,提示大肠癌组织中的抗原递呈功能下调是大肠癌组织逃避免疫监视的又一途径。随着大肠癌Dukes分期递进,肠癌组织中CTL细胞的密度逐步降低,肠癌细胞表面HLA-I类分子逐步下调,说明随着肠癌的演进,机体抗肿瘤免疫功能逐步减弱,肠癌逃避机体免疫监视的能力逐步增强;随着大肠癌分化程度降低,肠癌组织中淋巴细胞,树突状细胞的密度逐步降低,肠癌组织局部免疫功能逐步减弱。更多还原

【Abstract】 OBJECTIVE: To study the relationship between the expression of HLA molecules and clinicopathological significance in colorectal cancinoma.METHODS: Expressions of HLA class I and associated antigens were studied by immunohistochemistry in colorectal cancinoma, histologically normal mucosa adjacent to cancinima(<3cm),and histologically normal mucosa distant from cancinoma. The density of variety leukocytes in the tissue of cancinoma was studied also. Several monoclonal antibodies(mAbs) were used in this study. HC10 and HCA2 reacted with the nonmorphic determinant of heavy chain of HLA class I antigen; L368 reacted with ?2 microglobulin; SY1 reacted with LMP2 antigen;TO-5 reacted with calnexin;CD8 and S-100 reacted with T cells and DC.RESULTS: In colorectal cancinoma tissues, the expression of HLA –A, B/C, ?2M, LMP2 and calnexin were reduced compared to that of both in histologically normal mucosa adjacent to cancinoma and histologically normal mucosa distant from cancinoma(P=0.001).The expression of calnexin in cancinoma were reduced compared to that of both in histologically normal mucosa adjacent to cancinoma and histologically normal mucosa distant from cancinoma also(P=0.004). With the cancinoma Dukes phaging, the expression of HLA-B/C downregulated, which in Dukes A is higher than that in Dukes D(P=0.0262). 16.9% colorectal cancinoma expressed the HLA-II antigen, and the expression of the HLA class II molecules in the colorectal cancinoma was reduced compared to the normal tissue (P=0.001). With the Dukes staging of the colorectal cancinoma, the HLA-I antigen and the density of leukocytes and CTL reduced. With degree of colorectal differentiation, the density of DC dereased.CONCLUSION: The expression of HLA class I and associated protein were downregulated in the colorectal cancinoma tissue. It may be one important mechanism by which colorectal cancinoma cell escape from immune recognition. The calnexin,a kind of the chaperone molecules,and the LMP2,one of the antigen process molecules, expression downregulated in colorectal cancer,these antigens may effect the HLA class I molecules expression in the colorectal cancinoma. The results of density of dendritic cells declined and HLA class II expression downregulation suggested that potential of antigen process and present in the cancinoma was reduced compared to the normal tissue. The abnormality may provide tumor cells with a mechanism to escape from immune surveillance; With the Dukes staging of the colorectal cancinoma, the potential <WP=7>of host immunity declined and the potential of the colorectal cancinoma escape from immunity surveillance inreased. we follow up these patients, and the results showed that these patients with HLA downregulation have bad prognosis.更多还原