Ishikawa Y, Tokunaga K, Tanaka H, Nishimura M, Muraoka M, Fujii Y, Akaza T, Tadokoro K, Juji T
Department of Research, Japanese Red Cross Central Blood Center, Tokyo.
Immunogenetics. 1996;43(1-2):1-5. doi: 10.1007/BF00186597.
A healthy adult having no serologically detectable HLA class I A locus antigens was identified. The parents of the individual are consanguineous. Results of a family study indicated that the individual is homozygous for the B46-Cw1-DR8.1 haplotype, which was shown to be positively associated with A0207 in our previous study. The HLA-A null individual is healthy and exhibits no apparent immunological abnormality. Total RNAs extracted from peripheral blood were converted to cDNAs. The reverse transcriptase-polymerase chain reaction (PCR) product, which is of the same size as the normally expressed gene, was easily obtained from the cDNAs with HLA-A locus-specific primers. The nucleotide sequence of this null allele (A0215N) was the same as that of A0207 except for a single nucleotide substitution which resulted in a stop codon in exon 4. From its nucleotide sequence, a truncated molecule was expected to be produced; however, the immunoprecipitation study failed to detect the predicted product. Genomic DNAs from 29 unrelated individuals who expressed only one HLA-A antigen with HLA-B46, were analyzed by a PCR-sequence-specific oligonucleotide method. None of the samples possessed this stop codon. Therefore, A0215N is likely to be a rare allele generated by a single point mutation from A*0207.
发现一名健康成年个体在血清学上检测不到HLA I类A位点抗原。该个体的父母是近亲。一项家系研究结果表明，该个体为B46-Cw1-DR8.1单倍型纯合子，在我们之前的研究中显示该单倍型与A0207呈正相关。该HLA-A缺失个体健康，未表现出明显的免疫异常。从外周血中提取的总RNA被转化为cDNA。使用HLA-A位点特异性引物，很容易从cDNA中获得与正常表达基因大小相同的逆转录酶-聚合酶链反应（PCR）产物。该无效等位基因（A0215N）的核苷酸序列与A0207的序列相同，只是有一个单核苷酸替换，导致第4外显子出现终止密码子。根据其核苷酸序列，预计会产生一个截短的分子；然而，免疫沉淀研究未能检测到预测产物。通过PCR-序列特异性寡核苷酸方法分析了29名仅表达一种与HLA-B46相关的HLA-A抗原的无关个体的基因组DNA。所有样本均未出现这种终止密码子。因此，A0215N可能是由A*0207的单点突变产生的罕见等位基因。
