STUDY ON MACHINERY HLA CLASS I DOWNREGULATION ON MELANOMA CELLS.

(1) HLA I类抗原在黑色素瘤病变中的下调频率本研究旨在探讨HLA I类抗原在手术切除的黑色素瘤病变中的表达。为此，用单克隆抗体（mAb）对单态、位点特异性和多态抗原决定因子进行免疫过氧化物酶反应，对32例原发病变和11例转移病变进行染色。将黑色素瘤细胞的染色强度与肿瘤巢周围的角质形成细胞的染色强度进行比较。采用常规淋巴细胞毒性测定法测定患者HLA表型。约20%的原发病变和约50%的转移性病变未被单克隆抗体染色，或被单克隆抗体对单型和位点特异性抗原决定因子的染色强度降低。此外，约40%的原发病变和约60%的转移病变未被单抗到HLA I类同种特异性染色或低强度染色。这些结果表明HLA I类异常的频率在黑色素瘤病变中更高的表达。这些异常可能对基于T细胞的免疫治疗产生负面影响，因为它们为黑色素瘤细胞提供了一种逃避细胞毒性T细胞破坏的机制。(2)黑色素瘤细胞HLA I类下调机制。通过免疫过氧化物酶染色检测黑色素瘤病变中蛋白酶体亚基LMP2和LMP7、mhc编码转运体亚基TAP1和TAP2以及HLA类抗原的表达，因为这些分子在黑色素瘤相关抗原衍生肽向细胞毒性T细胞的递呈中起重要作用。在原发性和转移性病变中，LMP2的表达频率低于LMP7。TAP1、TAP2和HLA I类抗原的表达在转移性黑色素瘤中比在原发性黑色素瘤中更常下调。在大约60%的原发性和转移性黑色素瘤病变中观察到TAP1、TAP2和HLA I类抗原表达的同步下调。此外，原发性病变中的这些下调与病变的厚度、疾病的分期、疾病进展时间的缩短和生存期的缩短显著相关。这些结果表明TAP在黑色素瘤细胞HLA I类下调和疾病的临床过程中发挥重要作用，可能是通过在疾病进展过程中为黑色素瘤细胞提供逃避CTL识别的机制。少

(1) Frequency of HLA Class I downregulation in melanoma lesionsThe aim of this study was to investigate the expression of HLA Class I antigens in surgically removed melanoma lesions. To this end 32 primary and 11 metastatic lesions were stained in the immunoperoxidase reaction with monoclonal antibodies(mAb) to monomorphic, locus specific and polymorphic antigenic determinants. The intensity of staining of melanoma cells was compared to that of keratinocytes surrounding the tumor nest. The patients' HLA phenotype was determined utilizing the conventional lymphocytotoxicity assay. About 20% of primary and about 50% of metastatic lesions were not stained or were stained with reduced intensity by mAb to monomorphic and locus specific antigenic determinants. Moreover about 40% of primary and about 60% of metastatic lesions were not stained or were stained with low intensity, by mAb to HLA Class I allospecificities. These results indicate that the frequency of abnormalities in HLA Class I a … More ntigen expression is high in melanoma lesions. These abnormalities are likely to have a negative impact on T cell based immunotherapy, since they provide melanoma cells with a mechanism to escape from destruction by cytotoxic T cells.(2) Machinery of HLA Class I downregulation in melanoma cells.The expression of the proteasome subunits LMP2 and LMP7, the MHC-encoded transporter subunits TAP1 and TAP2 and HLA Class antigens was tested by immunoperoxidase staining in melanoma lesions, since these molecules play an important role in the presentation of melanoma associated antigen derived peptides to cytotoxic T cells. LMP2 was less frequentlt expressed than LMP7 in primary and metastatic lesions. TAP1, TAP2 and HLA Class I antigen expression was more frquently downregulated in metastatic than in primary melanoma lesions. A synchronous downregulation of TAP1, TAP2 and HLA Class I antigen expression was observed in about 60% of primary and metastatic melanoma lesions. Moreover, these downregulation in primary lesions was significantly associated with their thickness, with the stage of the disease, with a reduced time to disease progression and with a reduced survival. These results suggest that TAP plays an important role in HLA Class I downregulation in melanoma cells and in the clinical course of the disease, probably by providing melanoma cells with a mechanism to escape from CTL recognition during disease progression. Less