中文摘要：

目的：探讨胃癌细胞系MKN中HLA—Ⅰ类抗原表达水平异常的分子机制。方法：以胃癌细胞系BGC823、MGC803和SGC7901为对照，利用流式细胞仪检测细胞表面HLA—Ⅰ类复合物的表达情况，Western blot检测HLA—Ⅰ类分子重链及轻链表达情况，半定量RT—PCR检测HLA—Ⅰ类分子重链、轻链和抗原加工分子mRNA水平的表达情况，并利用HLA基因区域的微卫星序列检测MKN细胞HLA基因在DNA水平的完整性。结果：胃癌细胞系MKN表面HLA—Ⅰ类复合物表达降低，重链A及B／C位点蛋白无表达而轻链表达无异常。在mRNA水平，胃癌细胞系MKN存在重链A、B、C各位点和抗原加工分子TAP1、LMP2、Tapasin、PA28β的表达缺失。微卫星DNA扩增结果初步显示，MKN细胞无HLA基因区域DNA的大片段丢失。结论：胃癌细胞系MKN HLA—Ⅰ类分子复合物表达降低可能是由HLA-Ⅰ类分子重链及其加工分子在转录水平改变而引起的。

英文摘要：

Objective To investigate the mechanism of HLA class Ⅰ downregulation in a gastric cell line MKN Methods The expression of HLA class Ⅰ complex was determined by flow cytometry. Then the expression of HLA class Ⅰ heavy chain and light chain were detected by Western blot assay using a panel of antibodies. To characterize the downregulation of HLA class Ⅰ complex, the analysis was extended to RNA level by RT-PCR using specific primers. Results It was found that the expression of HLA class Ⅰcomplex in MKN cell was reduced in comparison with other gastric cell lines BGC823, MGC803 and SGC7901. HLA class Ⅰ heavy chain expression （A and B/C locus） was lost in MKN while the expression of the light chain was normal. RT-PCR showed that the expression of HLA class I heavy chain, TAP1, LMP2, Tapasin and PA28β mRNA were lost in MKN cells, while DNA of those genes might be intact by detecting microsatellite marker in HLA region. Conclusion cell line MKN might be due to low efficiency of HLA gene