Immunological Study Of Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is a chronic autoimmune disease in childhood with high incidence of disability. The etiology is still unknown. Mannose-binding lectin (MBL) is an important constituent of the innate immune system, and MBL bound to microbial surfaces decorated with a range of sugars is able to activate the complement system. MBL deficiency is believed to play an important role in infectious and autoimmune disease. Recently, two schools of thought were pointed out based on studies of MBL polymorphism and susceptibility with RA patients in different population. However, this possible link between MBL polymorphism and JIA has not been reported. Leukotriene B₄ (LTB₄) is a well-known mediator in early process of inflammation. G-protein coupled receptors BLT₁ and BLT₂ are the currently known LTB₄ receptors. These findings establish the LTB4-BLT pathway. LTB₄-BLT interaction plays an importmant role in defense mechanism and inflammation. Therefore, we investigate the association between MBL polymorphisms and LTB₄-BLT pathway with JIA disease.Part I Association of mannose-binding lectin gene polymorphisms with juvenile idiopathic arthritisObjective: To investigate the relationship between mannose-binding lectin (MBL) gene polymorphisms and susceptibility with juvenile idiopathic arthritis (JIA).Methods: Polymerase chain reaction-restrictive fragment length polymorphism (PCR-RFLP) and sequence specific priming-polymerase chain reaction (SSP-PCR) were used to investigate polymorphisms of codon 54 and 57 of exon 1 and 2 single nucleotide polymorphisms (SNP) at positions -550 and -221 in the promoter of the MBL gene in 93 patients of JIA and 48 healthy children.Results: (1) There did not show codon 57 polymorphism in both groups. Genotypic frequencies of codon 54 in group of JIA patients showed wild type 71.0%, heterozygous type 25.8% and homozygous type 3.2%; Genotypic frequencies of the codon 54 in healthy control group showed wild type 75.0%, heterozygous type 25.0% and homozygous type 0.0%. There did not show significant difference between JIA patients and control groups(P>0.05). (3) Three haplotypes, HY, LY, and LX, were present in both groups, and no HX haplotype was found. And no statistically significant differences were observed when the haplotype distributions between JIA patients and healthy controls were compared (P>0.05).Conclusion: Our results provide no evidence for genetic association conferred by the polymorphisms of MBL gene with respect to susceptibility of JIA. The mutation of the MBL gene may be not associated with juvenile idiopathic arthritis. Part II Study on the role of leukotriene B₄-leukotriene B₄ receptor 2 pathway in juvenile idiopathic arthritisObjective: To investigate whether leutriene B4-leutriene B₄ receptor 2 (LTB₄-BLT₂) pathway and tumor necrosis factor alpha (TNF-a) are involved in the immunity inflammation process of juvenile idiopathic arthritis (JIA) so as to understand the immunity mechanism of JIA.Methods: We cultivated monocyte/macrophage with serum of healthy children, serum of acute JIA patients and its convalescent respectively, and collected both themonocyte/macrophage and the conditioned media (MCM). Then we cultivated the endothelial cell with MCM, and collected the cells and supernatant. The expressions of BLT₂ on monocyte/macrophage and endothelial cell were detected by fluorescence activated cell sorter; The gene expression of TACE in monocyte/macrophage was determined by RT-PCR; The concentrations of LTB₄ and TNF-a in monocyte/macrophage or endothelial cell were measured by enzyme-linked immunosorbent assay (ELISA).Results: The serum from children of acute JIA disease intensely induced the production of LTB₄ and the expression of BLT₂ in monocyte/macrophage; The serum from children of acute JIA disease induced the expression of TACE and the production of TNF-a in monocyte/macrophage; The conditioned media from the culture system of monocyte/ macrophage raised with the acute serum of JIA patients, stimulated the expression of BLT₂ on endothelial cell.Conclusion: LTB4-BLT₂ pathway in monocyte/macrophage and endothelial cell activated one after another, participates in the immunity inflammation process of JIA; In the inflammatary process of JIA, the increased expression of TNF-a converting enzyme in monocyte/macrophage is the main reason of the elevated production of TNF-a.TACE inhibition may represent an additional therapeutic target for the treatment of JIA.