Study Of Killer Cell Immunoglobulin-Like Receptors Gene In Systemic Lupus Erythematosus

Background: systemic lupus erythematosus (SLE) is a typical non-organ-specific autoimmune diseases ,whose abnormal autoimmune phenotype almost covers the whole immune system and has been regarded as the prototype of autoimmune diseases. Outstanding character for the patients is varied serum autoantibodies,resulting in several systems and organs damaged. SLE is usually diagnosed in women in their childbearing years .Compared with the male peers, the ratio is 9:1. The prevalence of SLE varies about 10-100/10~6 between ethnic groups, 70/10 million in China and 1:1000 in Chinese women.The etiology and pathogenesis of SLE is not very clear. An extremely complicated and multifactorial interaction among various genetic,sex hormone and environmental factors is probably involved. On one hand,these factors change the structure of DNA ;on the other hand,they activate the immune system, causing a serious immunological dysfunction. SLE is characterised by a myriad of immune system aberrations that involve NK cells, T cells, resulting in the activation of the polyclonal B cell, production of autoantibody, and formation of immune complex, leading to the chronic inflammation of multiple organ. Immunological disturbance plays a vital role in the process of SLE. Many studies have confirmed pathogenesis of SLE is closely related with lymphocyte subsets imbalance. In SLE ,B cells produce autoantibodies was dependent on T cells,so T cell play an important role in the pathogenesis of SLE. In SLE, recognition of self-antigen T cells and reaction is determined by the MHC class I and II molecules. In patients of SLE T-cell is exciting and prone to immune response. T-cell in Lupus mouse can be proliferated by stimulation of low doses antigen and IL-2 is significantly increased. Studies suggest that the T cell in lupus the biological character of T cell has changed: the threshold value decreases. Stimulated by self-antigen,T cell is easily activated rather than "incompetent".Killer cell immunoglobulin-like receptors (KIR) are a highly diverse family of receptors expressed by natural killer cells and subsets of T lymphocytes. KIR are glycoproteins of Ig superfamily that modulate cells function upon recognition of MHC class I molecules. In humans, The KIR locus, containing a family of polymorphic and highly homologous genes, maps to chromosome 19q13.42 within the leukocyte receptor complex (LRC).Up to date, 14 expressed KIR genes and 2 pesudogenes were identified. Besides allelic polymorphism, haplotype diversity is a significant component of human KIR gene diversity as well. It is the characteristic feature same as the HLA-DR that KIR haplotype diversity is variability in the quantity and quality of the genes they contain. Based on gene content, the haplotypes have been divided into two primary sets, termed A and B, the most functionally relevant distinction between haplotypes A and B is the number of stimulatory receptors present. According to the cytoplasmic domain of the length and the existence of ITIM (immunorecept or tyrosine-based inlibitory motify) or not, KIR receptor divide into inhibition (KIR-L) and activation (KIR-S). The inhibitory receptors have a longer cytoplasmic tail containing immunoreceptor-tyrosine-based inhibitory motifs (ITIM). Activating forms have a relatively short cytoplasmic tail and contain a positively charged residue in the transmembrane region that interacts with immune tyrosine-based activation sequence (ITAM). In humans, inhibitory receptors that recognize classical MHC class I molecules.KIR2D bind to HLA-Cw molecules. In the KIR structures, the tandem immunoglobulin-like domains (D1 and D2) recognize respectively the α 1 and α 2 domain of HLA-Cw ligand. Dimorphisms in the HLA-Cw al domain that are characterized by Ser77/Asn80 and Asn77/Lys80 define serologically distinct allotypes of HLA-Cw (Cw group 1 and group 2, respectively). KIR2DL2/3 receptors recognize HLA-C*01, *03, *07, and *08, all of which share a serine at position 77 and an asparagine at position 80 (S77, N80). In contrast, KIR2DL1 receptors are specific for HLA-C alleles that have asparagine at residue 77 and lysine at position 80 (N77, K80).Amino acid residues at position 80 is important places, it distinguishes different HLA molecules, and the amino acid residues at position 77 were decided on KIR combination. KIR binding specificity for MHC - I molecules transmit activate or inhibit signal, play a vital regulatory role in the congenital and acquired anti-tumor immunity , anti-viral immune response, immune homeostasis and tolerance. In recent years, the role of KIR in autoimmune diseases has received increasing attention. The frequency of activing KIR gene is associated with rheumatoid arthritis vasculitis. seronegative spondyloarthropathies disease, scleroderma, psoriasis, type 1 diabetes and so on.Objective : To investigate Killer-cell immunoglobulin-like receptors (KIR) gene diversity in SLE .To discussion the association of KIR-HLA receptor ligand with systemic lupus erythematosus, and to analysis correlation of KIR gene and KIR-HLA receptor ligand with SLE clinical phenotype.Method : 1 93 SLE patients and 123 sex matched healthy controls were enrolled to detect the KIR genotype using PCR/SSP. We augmented 15 KIR genes: KIR2DL1-5, 3DL1-3, 2DS1-5, 3DS1 and pseudogene KIR2DP1 .Two different primer sets were designed for each gene except KIR2DS5. The KIR gene frequencies and genotype frequencies in SLE patients and control subjects were analyzed. 2. HLA-C 01-08 genotype frequencies in 88 patient with SLE and 86 health control from method 1 were determinated by pcr-ssp .We analyzed association of HLA-C/KIR combinations with SLE.3 We analyzed associations of the clinical and laboratory features with KIR genes and KIR2DS1+2DL2-HLA-Cw(-)of patients with SLE.Results : 1: The comparison of the distribution of KIR gene frequencies between the patients with SLE and the control group: Compared with the control group, KIR2DS1 and KIR2DL2 (p <0.001) gene frequencies was significantly increased in patient with SLE. Significant differences for other loci were not observed.2 The comparison of KIR gene frequency between the patients with different ages at onset of SLE: according to age at onset of the disease ,patients were divided into three subgroups,age at onset(AAO) ≤20(n=28),AAO 21-39(n=43),AAO≥40(n=17),but in this case KIR gene frequency was not correlated with age at disease onset.3 Distribution of activing KIR gene: individuals with two or more activating KIR genes were more frequently patients than control subjects (80.7 vs. 66.7%, respectively, P=0.025).4 Distribution of genotypes frequency in the patients with SLE and the control group: :57 different KIR genotypes were found in the tested patients and controls. Thirty genotypes were present in the patient group, and forty in controls. 30 of 57 genotypes have already been described by others. However, 27 genotypes were found for the first time.5 The comparison of the genotype between SLE and control group: the genotype most frequent (16.13%) in the SLE group, 3DL3~+, 2DS2~-, 2DL2~+, 2DL3~+, KIRZ~+, 2DL1~+, 2DL4~+ 3DL1~+ 3DS1~-, 2DL5~-, 2DS3~-, 2DS5~-, 2DS1~+, 2DS4~+, 3DL2~+ was significantly less frequent in the controls (0.81%, p< 0.001). On the other hand,The genotype the most frequent in controls, 3DL3~+, 2DS2~-, 2DL2~-, 2DL3~+, KIRZ~+, 2DL1~+, 2DL4~+, 3DL1~+, 3DS1-, 2DL5~-, 2DS3~-, 2DS5~-, 2DS1~-, 2DS4~+, 3DL2~+ (present in 19.51% of individuals), was much less frequent in SLE (5.38%; p=0.004). These two KIR genotypes differ only by the presence or absence of the KIR2DS1 and KIR2DL2 locus.6 KIR-2D/HLA-Cw combinations analysis: We analyzed combinations of activating/inhibitory KIR-2D and their HLA-Cw ligands for possible association with SLE. The results showed that analyses for KIR/HLA-Cw combinations did not reveal statistically significant association.7 Comparison activating KIR2D while absence of ligands for corresponding inhibitory KIRs between SLE and control group: : We analyzed the frenquency of activating KIR2D with combination KIR2DL/HLA-C absenting. The frenquency of KIR2DS1 was increased when KIR2DL1/HLA-Cw was absent in SLE, and the difference was significant.8 The relation between the clinical features of KIR gene and patients with SLE and the laboratory examination : KIR2DS5 positive individuals, alopecia patients were significantly higher than those in patients without several alopecia. The difference was statistically significant (p = 0.005). Patients with neurological disorder were significantly higher than KIR3DS1 negative individuals. The difference was significant (P = 0.013). Laboratory examination of immunoglobulin, complement, erythrocyte sedimentation rate and autoantibodies were not correlation with KIR gene.9 KIR2DS1 (+) 2DL1-HLA-Cw (-) gene was not correlated with clinical manifestations and laboratory examination of SLE.Conclusion : 1 The increased frequences of KIR2DS1 while absence of corresponding KIR2DL1/HLA-Cw pairs may be one of the susceptibility genes of SLE. When a single expression of KIR2DS1.Absence of ligands for inhibitory KIRs could potentially lower the threshold for NK (and/or T) cell activation mediated through activating receptors, thereby contributing to attack self cells and becoming the basis of autoimmune disease .2 In SLE patients KIR2DS5 is very likely that the impact of alopecia factor (P = 0.005). KIR3DS1 may be one of the reasons for occurrence of neuropsychiatric lupus. Different KIR gene may be contribute to different clinical features.3 The disorder of KIR gene may break the balance between receptors of NK cells and T-cell, making the immune cell dysfunction. This may be one of immune genetic factors of a diverse array of clinical manifestations and the pathogenesis of SLE.