Molecular Analyses of the Genetic Control of Immune Response in Humans

HLA类多基因家族由DR、DQ和DP基因组成。由于HLA-DR在T细胞-抗原提呈细胞相互作用中对外来抗原的应答存在遗传限制，并且抗HLA-DR单克隆抗体完全消除免疫应答，因此，人们普遍认为HLA-DR是免疫应答（Ir-）基因。在人群中，无论是自然致敏还是计划免疫，对血吸虫抗原、链球菌抗原、破伤风类毒素、乙型肝炎疫苗等天然抗原都有低（无）应答。家族分析显示，对这些抗原的低（非）反应性存在于hla相关的显性遗传性状中，因此低（非）反应不能用一组lr基因来解释。此外，在体外低应答者（非应答者）中，通过剔除CD8+ T细胞或添加抗HLA-DQ单克隆抗体可以恢复强免疫应答，这表明HLA-DQ可能通过诱导CD8+抑制性T细胞来控制抗原特异性低免疫应答。通过序列特异性寡核苷酸探针与聚合酶链反应扩增的HLA基因杂交，确定了对链球菌抗原低应答和高应答的HLA- dq等位基因。观察到特定HLA-DQ等位基因与低或高应答者之间的强关联，高应答者和低应答者单倍型的杂合子表现出低应答性，证实HAL-DQ连锁基因控制对链球菌抗原的低应答性是一个显性遗传性状。在对链球菌抗原反应低（无）的外周血淋巴细胞中，分别观察到受HLA-DR和DQ限制的CD4+ T细胞，以及受到抗原攻击的一小部分CD8+ T细胞。另一方面，在高应答者中，仅检测到受HLA-DR限制的CD4+ T细胞。低应答者受HLA-DQ限制的CD4+T细胞利用T细胞受体Vbeta5.3基因识别链球菌M蛋白，增殖活化CD8+T细胞，而受DR限制的CD4+T细胞则不能。CD8+ T细胞表达T细胞受体V α 2和Vbeta5.2基因，抑制CD4+ T细胞的抗原特异性增殖反应。因此，我们得出结论，HLA-DQ等位基因控制人类低（非）反应性作为免疫抑制（Is）基因。采用上述的DNA分型方法检测胰岛素依赖型糖尿病（IDDM）患者的HLA-DQ等位基因，结果显示胰岛素依赖型糖尿病的易感性和耐受性之间存在较强的相关性。这种与HLA-DQ相关的IDDM易感性或抗性可能是通过HLA-DQ作为is基因对免疫反应的遗传控制来解释的。为了在体内建立模型小鼠，分析HLAⅱ类分子的生物学功能，将HLA- dqw6 a和B基因导入C57BL/6 （B6）小鼠受精卵，建立了HLA- dqw6转基因B6小鼠（DQw6-B6）稳定系。DQw6-B6获得了对SCW的免疫应答，而对大肠杆菌抗原失去了免疫应答。因此，我们通过引入人MHC II类基因成功地改变了小鼠的免疫反应。少

HLA class multigene family consists of DR, DQ and DP genes. It is well accepted that HLA-DR acts as immune response (Ir-) gene, because there is a genetic restriction by HLA-DR in T cell-antigen presenting cell interation to respond to foreign antigens, and because anti HLA-DR monoclonal antibody completely abolish the immune response. In human population, there are low (non) responders to natural antigens such as schistosomal antigen, streptococcal antigen, tetanus toxoid, hepatitis B vaccine, etc. after either natural sensitization or planned immunization. Family analysis revealed that the low (non) responsiveness to those antigens in an HLA-linked dominant genetic trait, and therefore the low (non) response can not be explained by a lock of lr-genes. Furthermore strong immune response can be restored in low (non) responders in vitro by either delection of CD8+ T cells or addition of anti HLA-DQ monoclonal antibody suggesting that HLA-DQ may control the antigen specific low immune re … More sponsiveness through an induction of CD8+ suppressor T cells.HLA-DQ alleles of the low and high responders to streptoccocal antigen were determined by investigating a hybridization between sequence specific oligonucleotide probes and HLA genes amplified by polymerase chain reaction. The strong associations between particular HLA-DQ alleles and low or high responders were observed and heterozygotes of high and low responder haplotypes exhibited low reponsiveness confirming that the HAL-DQ linked gene controlled low responsiveness to streptococcal antigen as a dominant genetic trait. In the peripheral blood lymphocytes from low (non) responders to streptococcal antigen, CD4+ T cells restricted by HLA-DR and DQ, respectively, were observed as well as a small fraction of CD8+ T cells if challenged with the antigen. In high responders, on the other hand, only CD4+ T cells restricted by HLA-DR were detected. CD4+ T cells restriced by HLA-DQ in low responders recognized streptococcal M protein by utilizing T cell receptor Vbeta5.3 gene and propagated the proliferation and activation of CD8+T cells whereas CD4+T cells restricted by DR could not do so. The CD8+ T cells expressed T cell receptor V alpha2 and Vbeta5.2 genes and suppresed the antigen specific proliferative response of CD4+ T cells. Thus we conclude that HLA-DQ alleles controls low (non) responsiveness in humans as immune suppresssion (Is) genes. HLA-DQ alleles of the patients with Insulin dependent diabetes mellitus (IDDM) were determined by DNA typing methods desribed above to show strong association between susceptibility or resistance to IDDM. This HLA-DQ associated susceptibility or resisitance to IDDM may be explained by the genetic control of immune response via HLA-DQ as the Is-gene.In an attempt to establish a model mouse for the analysis of biological function of HLA class II molecules in vivo, both the HLA-DQw6 A and B genes were introduced into fertilized eggs of C57BL/6 (B6) mice and a stable line of HLA-DQw6 transgenic B6 mouse (DQw6-B6) was established. The DQw6-B6 acquired an immune responsiveness to SCW and lost an immune responsiveness to E. Coli antigen. Therefore, we succeeded in the alteration of mouse immune response by introducing human MHC class II genes. Less