| Objective HLA-B27 belongs to major histocompatibility complex(MHC) I type molecular. It may play an important role in the pathogenesis of ankylosing spondylitis(AS). But it was little known to the roles of the intensity of HLA-B27 and its subtypes in AS. To investigate whether the expression intensity of HLA-B27 and its subtypes associated with incidence of AS, the expression of HLA-B27 and its subtypes along with other laboratory parameters were detected in patients with AS. Another aim of this study was to investigate the possible significance of HLA-B27 expression and its subtypes in the early diagnosis and treatment to patients with AS.Methods 120 cases patients suspected with AS and 50 healthy subjects were enrolled in the study. Main demographic and clinical characteristics of the subjects were collected, including age, sex, family history and disease activity index in AS. While ESR and other relative laboratory parameters were acquired as protocols. The expression of HLA-B27 protein were detected by immunomagnetic separation and enzyme-linked immunosorbent assay(IMS-ELSIA) in all subjects. Meanwhile total RNA was isolated from peripheral blood and RT-PCR was used to measure the quantitative expression of HLA-B27 gene. Based on the RT-PCR, sequence-based typing(SBT) method was used to confirm the HLA-B27 subtype. And the groups were divided by the subtype by different base sequence. All experimental data were analyzed by SPSS 17.0 software and P values<0.05 were considered to be significant.Results Firstly, there were 55 subjects were finally diagnosed as AS patients among the 120 patients suspected with AS. Two kinds of ways were used to detected the expression of HLA-B27, which were IMS-ELISA and PCR-SBT, respectively. The positive rates of HLA-B27 detected by IMS-ELISA and PCR-SBT were 37.50%(45/120),45.83%(55/120), respectively. The sensibility and specificity of IMS-ELISA method were 69.09%,89.23%, respectively. While the sensibility and specificity of PCR-SBT were 96.36%,96.92%, respectively. Area under the curve of two methods were 0.792,0.966, separately. So PCR-SBT was better than the other one in detecting HLA-B27(P=0.032). Secondly, there were 53 subjects with HLA-B27 positive(96.36%) in 55 patients with AS. Five subtypes were found and which were HLA-B27:04 subtype (29/53,54.72%), HLA-B27:05 subtype(20/53, 37.74%), HLA-B27:02 subtype(2/53,3.77%), HLA-B27:03 subtype(1/53,1.89%) and HLA-B27:07 subtype(1/53,1.89%). Among the 50 healthy subjects, there were only one kind of subtype of HLA-B27(2/50,4%). They were all men and the subtype is HLA-B27:04. Thirdly, There were no statistical difference in the age (t=0.711, P=0.480), sex (x2=0.880, P=0.348), family history (x2=0.011, P=0.916) and treatment (χ2=0.113,P=:0.736)between the HLA-B27:04 and HLA-B27:05 subtypes. Similarly, there were also no difference in clinical characteristics and general laboratory parameters between the two groups (P>0.05). Furthermore, there were no difference in the expression of HLA-B27 antigen (t=1,675, P=0.101) and gene (t=1.137,P=0.261) between HLA-B27:04 and HLA-B27:05 subtypes. Fourthly, the correlation was analyzed between the clinical general parameters and the expression intensity of HLA-B27 among the 53 AS subjects which HLA-B27 was positive. A positive correlation existed between Bath Ankylosing Spondylitis disease activity(BASDAI) and ESR, IgA, IgG (r=0.3354, P=0.009; r=0.275, P=0.046; r=0.299, P=0.029). However, there was no correlation between BASDAI and CRP, IgM (r=0.177, P=0.205; r=0.208, P=0.134). Further analysis showed that there was a positive between BASDAI and the expression intensity of HLA-B27 protein and gene(r=0.562, P=0.000; r=0.845, P=0.000). Besides, a positive correlation existed between the expression of HLA-B27 protein and gene(r=0.413, P=0.002).Conclusion HLA-B27:04 and HLA-B27:05 were primary subtypes in patients of AS. There was a correlation between the expression intensity of HLA-B27 and the AS disease activity index. The expression of HLA-B27 intensity could provide important information for estimating the condition of AS patients. The expression intensity of HLA-B27 and its subtype analysis could offer basis for early screening of AS disease and estimating the disease status. The study may apply a new viewpoint in exploring the pathogenesis of AS. |
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