Natural Killer Cells Offer Differential Protection From Leukemia in Chinese Southern Han

Interactions of human natural killer (NK) cell inhibitory receptors with polymorphic HLA-A, -B and -C molecules educate NK cells for immune surveillance against tumor cells. The KIR A haplotype encodes a distinctive set of HLA-specific NK cell inhibiting receptors having strong influence on immunity. We observed higher frequency of KIR A homozygosity among 745 healthy Chinese Southern Han than 836 adult patients representing three types of leukemia: ALL (OR = 0.68, 95% CI = 0.52-0.89, p = 0.004), AML (OR = 0.76, 95% CI = 0.59-0.98, p = 0.034), and CML (OR = 0.72 95% CI = 0.51-1.0, ns). We observed the same trend for NHL (OR = 0.47 95% CI = 0.26-0.88 p = 0.017). For ALL, the protective effect of the KIR AA genotype was greater in the presence of KIR ligands C1 (Pc = 0.01) and Bw4 (Pc = 0.001), which are tightly linked in East Asians. By contrast, the C2 ligand strengthened protection from CML (Pc = 0.004). NK cells isolated from KIR AA individuals were significantly more cytotoxic toward leukemic cells than those from other KIR genotypes (p < 0.0001). These data suggest KIR allotypes encoded by East Asian KIR A haplotypes are strongly inhibitory, arming NK cells to respond to leukemogenic cells having altered HLA expression. Thus, the study of populations with distinct KIR and HLA distributions enlightens understanding of immune mechanisms that significantly impact leukemia pathogenesis.

Assessment of HCV genotypes in Yunnan Province of Southwest China

Recently, we reported that the frequency of hepatitis C virus (HCV) genotypes and subtypes has rapidly changed among intravenous drug users (IDUs) in Yunnan Province over the last 5 years; this is especially true for subtype 6a which has increased in frequency from 5 to 15%. Here, we assessed 120 HCV-positive plasma samples from the general population (GP). HCV NS5B fragments were amplified and sequenced by PCR. We identified four HCV genotypes (1, 2, 3 and 6) and seven HCV subtypes (1b, 2a, 3a, 3b, 6a, 6n, and 6k) in this population. Genotype 3 was predominant, with a distribution frequency of 0.484, followed by genotype 1 (0.283), genotype 6 (0.133) and genotype 2 (0.100). HCV subtypes 3b (frequency 0.292) and 1b (frequency 0.283) were the most common subtypes. A comparison of the current data with previous results reported for IDUs showed that the distribution frequencies of genotypes 1, 2 and 6 were significantly different between patients in the GP and IDUs (P < 0.05). Among the HCV subtypes, the distribution frequencies of 1b, 2a, 6a, and 6n were significantly different between patients in the GP and IDU groups (P < 0.05). Moreover, Phylogenetic analyses showed that HCV subtype 6a strains isolated from IDUs and the GP were intermixed and not separately clustered. HCV subtype 6a was predominant not only among IDUs but also among those in the GP in the Guangdong Province and Vietnam. However, HCV subtype 6a was predominant only among IDUs and not among those in the GP in the Yunnan and Guangxi Provinces. Our results indicate that the HCV subtype 6a could rapidly spread across China.

Distribution of HLA-A, -B, and -C alleles and HLA/KIR combinations in Han population in China

We investigated polymorphisms of the human leukocyte antigen (HLA) class I (A, B, and C) loci of a Han population (n, 239) from the Yunnan province, Southwest China, using high-resolution polymerase chain reaction-Luminex (PCR-Luminex) typing. We combined the HLA data from this study with the KIR genotypes from a previous study of this Han population to analyze the combination of KIR/HLA ligands. A total of 27 HLA-A, 54 HLA-B, and 31 HLA-C alleles were found in this population. The frequencies of A*11:01, A*24:02, B*40:01, B*46:01, C*01:02, C*03:04, and C*07:02 were all > 10%. The following haplotypes were common, with frequencies > 5%: 1 A-B (A*02:07-B*46:01), 2 A-C (A*02:07-C*01:02, and A*11:01-C*07:02), 4 C-B (B*13:01-C*03:04, B*40:01-C*07:02, B*46:01-C*01:02 and B*58:01-C*03:02), and 1 A-C-B (A*02:07-C*01:02-B*46:01). Analysis of KIR3D and their ligands HLA-A3/A11 and HLA-Bw4 showed that the frequencies of 3DL2⁺-A3/A11⁺ and 3DL2⁺-A3/A11⁻ were 0.527 and 0.473, and the frequencies of 3DL1⁺-Bw4⁺, 3DL1⁺-Bw4⁻, 3DL1⁻-Bw4⁺, and 3DL1⁻-Bw4⁻ were 0.552, 0.397, 0.038, and 0.013, respectively. The results of KIR/HLA-C combination analysis showed that all individuals had at least one inhibitory or activating KIR/HLA-C pair, and one KIR/HLA-C pair was the most frequent (157/239), followed by two pairs (46/239), three pairs (33/239), and no pairs (3/239). Comparison of KIR gene and HLA gene and their pair frequency between Yunnan Han and the isolated Han (FYDH) who also lived in Yunnan province showed no significant difference (P > 0.05) in KIR frequencies, but significant differences (P < 0.05) for some HLA allele frequencies. In addition, there was no significant difference (P > 0.05) between the two populations for KIR/HLA pairs.

Killer cell immunoglobulin-like receptor (KIR) genes in 4 distinct populations and 51 families in mainland China

In this study, we investigated the killer cell immunoglobulin-like receptor (KIR) genes and HLA-C1/C2 dimorphism in 819 healthy, unrelated individuals composed of two southern Chinese Han populations (Hunan Han and Guangdong Han) and two northern Chinese populations (Inner Mongolia Han and Inner Mongolia Mongol), using polymerase chain reaction-sequence-specific priming (PCR-SSP) method. Fifty-one Chinese families were used to determine KIR haplotypic configuration. Our data showed that KIR2DL4, KIR3DL2, KIR3DL3, and KIR3DP1 genes were present in all of the 819 individuals. However, KIR2DL4 and KIR3DP1 genes were not detected in two members of a northern Chinese family. None of the KIR genes showed significant difference between the four populations. Thirty-five different KIR gene profiles were identified, one of which has not been previously reported in the Allele Frequencies KIR database. Eleven distinct KIR haplotypic configurations were determined through family analysis. Individuals with KIR2DLl and KIR2DL3 genes but lacking KIR2DSl and KIR2DS2 genes, coupled with HLA-C1 (Asn(80)) homozygosity, predominated in each population. At least one known inhibitory KIR-HLA pair was detected in each individual. The findings shown here are valuable for future studies of the potential role of KIR genes as well as KIR-HLA interaction in disease susceptibility in related ethnic groups.