3123

HLA-DRB1

DRB1|DRw10|HLA-DR1B|HLA-DRB|SS1;major histocompatibility complex, class II, DR beta 1;HLA-DRB1;major histocompatibility complex, class II, DR beta 1

DW2.2/DR2.2|HLA class II histocompatibility antigen, DR-1 beta chain|MHC class II HLA-DR beta 1 chain|MHC class II HLA-DR-beta cell surface glycoprotein|MHC class II HLA-DRw10-beta|MHC class II antigen|human leucocyte antigen DRB1|lymphocyte antigen DRB1

6p21.3

protein-coding

Count: HLA-DRB1; 3123

The aetiology of chronic thromboembolic pulmonary hypertension (CTEPH) is largely unknown and may be heterogeneous, because there are several ethnic differences in the clinical characteristics of CTEPH. Female predominance and a higher ratio of chronic to acute pulmonary thromboembolism have been reported in Japan as compared with the USA. Because such ethnic differences may be controlled by genetic factors, the current study investigated HLA polymorphisms in Japanese patients with CTEPH. HLA typing by serological and/or DNA typing methods was performed (for HLA-A, B, DPB1, DRB1) in 80 patients and 678 controls, and the association of clinical characteristics with HLA alleles was studied. The frequencies of HLA-B*5201 (40 versus 24%) and DPB1*0202 (19 versus 6%) were significantly higher in the patients. HLA-B*5201 positive patients showed a significant female predominance. Total pulmonary vascular resistance and mixed venous oxygen tension were better in the HLA-B*5201 positive patients. In contrast, cardiac index and gas exchange parameters were worse in the HLA-DPB1*0202 positive patients. In the patients carrying HLA-B*5201 and/or -DPB1*0202, the frequency of deep vein thrombosis was significantly lower than the other patients. These observations suggested that both the susceptibility and clinical characteristics of chronic thromboembolic pulmonary hypertension were controlled in part by the HLA-B and -DPB1 loci.

The aim of this study was to compare the frequency of the HLA-DRB1 and HLA-DQB1 alleles in Korean patients with idiopathic pulmonary arterial hypertension (IPAH) and in normal controls and to determine any association that may exist between clinical characteristics of IPAH and specific HLA alleles. IPAH patients seen between October 1998 and September 2001 were retrospectively assessed, and 19 patients and 193 controls were HLA typed at the HLA-DRB1 and DQB1 loci. Clinical characteristics and hemodynamic parameters were reviewed. The patients with IPAH had a significantly higher frequency of the HLA-DRB1*0406 allele (18% vs. 6%, p = 0.004) and the HLA-DQB1*0302 allele (24% vs. 12%, p = 0.034), as well as a significantly higher frequency of haplotype DRB1*0406-DQB1*0302 (p = 0.0006). All 6 patients with haplotype DRB1*0406-DQB1*0302 (H+ group) were women, compared with 8 of the 13 patients lacking the DRB1*0406-DQB1*0302 haplotype (H- group), but without statistical significance. Three of 19 patients showed a positive short-term hemodynamic response to NO inhalation, all 3 of whom had the DRB1*0406-DQB1*0302 haplotype. There were no other significant differences in clinical characteristics and hemodynamic parameters between the H+ and H- groups. We conclude from this study that the HLA-DRB1*0406-DQB1*0302 haplotype is associated with IPAH in Korean patients. These results suggest that certain clinical characteristics of IPAH may be controlled in part by patients' HLA alleles.

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by pulmonary hypertension caused by thromboembolism of the pulmonary artery. Etiology of CTEPH may be heterogeneous and is largely unknown, but genetic factors are considered to be involved in the etiology. It has been reported that deep vein thrombosis (DVT) and/or coagulation factor variants are predisposing factors to CTEPH. However, more than half of the CTEPH patients, especially the Japanese, do not have prior DVT or coagulation abnormality, suggesting that there should be other risk factors for CTEPH. Moreover, there are several reports on the association between CTEPH and human leukocyte antigen (HLA). To further clarify the HLA-linked gene(s) controlling the susceptibility to CTEPH, 160 patients (99 without DVT and 61 with DVT) and 380 healthy controls were analyzed for polymorphisms in 15 microsatellite markers and 5 genes in the HLA region. We found a strong association of HLA markers with the DVT-negative CTEPH, DPB1(*)0202 (odds ratio (OR)=5.07, 95% confidence interval (CI)=2.52-10.19, P=0.00000075, corrected P-value (Pc)=0.00014), IKBL-p(*)03 (OR=2.33, 95% CI=1.49-3.66, P=0.00017, Pc=0.033) and B(*)5201 (OR=2.47, 95% CI=1.56-3.90, P=0.000086, Pc=0.016), whereas no significant association was observed for the DVT-positive CTEPH. The comparison of clinical characteristics of patients stratified by the presence of susceptibility genes implied that the DPB1 gene controlled the severity of the vascular lesion, whereas the IKBL gene (NFKBIL1) was associated with a relatively mild phenotype.