Clinical features of sarcoidosis in relation to HLA distribution and HLA-DRB3 genotyping by PCR-RFLP

The prevalence of HPA-1a alloimmunization and the potential risk of FNAIT depend on both the DRB3*01:01 allele and associated DR-DQ haplotypes

Alloimmunization against human platelet antigen (HPA)-1a during pregnancy can cause foetal/neonatal alloimmune thrombocytopenia (FNAIT) and severe bleeding in the foetus or newborn and likely depends on several factors. HPA-1a alloimmunization is associated with DRB3*01:01, which is associated with several DR-DQ haplotypes. However, it is not known to what extent these haplotypes contribute to the prevalence of HPA-1a alloimmunization. HPA-1a-alloimmunized women, identified in a prospective study, and random donors were typed for selected DRB3, DRB4, DRB1, DQA1 and DQB1 alleles to determine allele and DR-DQ haplotype frequencies. DRB3*01:01 was carried by 94% HPA-1a-immunized women compared to 27% in the general population. In the first population, the DR3-DQ2 haplotype was overrepresented (P < .003). The prevalence of HPA-1a alloimmunization was estimated to be about twice as frequent with DR3-DQ2 compared to DR13-DQ6, together accounting for about 90% of DRB3*01:01-positive individuals. Further, we examined DQB1*02 and DRB4*01:01 alleles for their reported association with HPA-1a alloimmunization, in the context of DR-DQ haplotypes. Since ~ 80% of DQB1*02 alleles are linked to the DR3-DQ2 haplotype, the association might be coincidental. However, the DQB1*02:02-associated DR7-DQ2 haplotype was also overrepresented in alloimmunized women, suggesting a role for this allele or haplotype in HPA-1a alloimmunization. As DRB4*01:01 is predominantly associated with the DR7-DQ2 haplotype in HPA-1a-alloimmunized individuals, the reported association with FNAIT may be coincidental. Typing for DR-DQ haplotypes revealed important genetic associations with HPA-1a alloimmunization not evident from typing individual alleles, and the presence of different DRB3-associated DR-DQ haplotypes showed different prevalence of HPA-1a alloimmunization.

The prevalence of antibodies against the HLA-DRB3 protein in kidney transplantation and the correlation with HLA expression

Human leukocyte antigen (HLA)-DRB3 is a functional HLA class II gene, which has a limited allele diversity in the human population. Furthermore, the HLA-DRB3 gene is only present in a subset of individuals. Therefore, in organ transplantation, this HLA molecule is frequently mismatched between patient and graft donor and thus antibodies against this mismatched HLA molecule can develop. In this study, we aimed to evaluate the prevalence and reactivity of these antibodies and aimed to identify factors that underlie antibody formation against HLA-DRB3. We showed in our patient cohort that HLA-DRB3 antibodies are identified in about 7% of all patients that were screened with solid phase assays. In these assays, we observed multiple antibody reactivity patterns indicating that HLA-DRB3 harbours multiple epitopes. In those cases, where we succeeded at tracing back the induction of these antibodies to the molecular HLA typing of the immunogenic event, we noticed a different frequency of HLA-DRB1 allele groups in the donors as compared to a control group. To a certain extent this distribution (e.g. HLA-DRB1*11 individuals) could be linked to an altered expression level. However, it also appears that different HLA-DRB3 alleles (e.g. HLA-DRB3*01 group) vary in their immunogenicity without having an expression difference. In conclusion, our study provides information on the immunogenicity and reactivity patterns of antibodies against HLA-DRB3 in kidney transplantation, and it points towards the possibility of HLA expression as a factor underlying antibody formation.

Retrospective study on the effects of immunosuppressive therapy in uveitis associated with rheumatic diseases in Korea

This retrospective study of 432 patients was conducted between 2000 and 2009 to compare immunosuppressive therapy responses in uveitis accompanied or unaccompanied by rheumatic diseases. We divided patients into two groups: uveitis related or unrelated to rheumatic diseases. The clinical improvement after treatment was measured at the end of the observation period. Of the 432 patients with uveitis, 33 (7.6%) patients suffered from associated rheumatic diseases and 399 (92.4%) patients did not. The groups showed similar clinical features, but the mean age at onset of uveitis was lower in the rheumatic disease group (44.06 ± 2.13 years vs. 48.23 ± 0.81 years). The rheumatic diseases included spondyloarthropathy (31%), Behcet's disease (27%), rheumatoid arthritis (18%), systemic lupus erythematosus (15%), Sjogren's syndrome (6%), and mixed connective tissue disease (3%). Erythrocyte sedimentation rate and C-reactive protein level were increased in uveitis associated with rheumatic diseases, whereas ocular complications were not. The response to immunosuppressive therapy was significantly increased in cases of uveitis associated with rheumatic diseases (P < 0.05). Therefore, during early treatment, uveitis accompanied by rheumatic diseases showed better response to immunosuppressive therapy and less frequent complications.

[Sarcoidosis and genetics]

Familial features of sarcoidosis and observations in monozygotic twins affected by the condition suggest the presence of a genetic predisposition. Various genetic associations have been described with genes coding for proteins involved in immune regulation in particular at the level of interaction between T-lymphocyte and antigen presenting cell. We review the various genetic targets described with techniques ranging from classic human lymphocyte antigen genotype to genome wide linkage scans. The 6p21 region has been highlighted, which includes relevant genes such as MHC class II, BTNL2 and TNFα. These studies show that the genetics of sarcoidosis are complex, that patient sub-groups exist, which may explain some of the heterogeneity in the results of genetic studies and that the interactions between genetic and environmental factors remains to be elucidated.

Immunogenetics of drug-induced skin blistering disorders. Part II: Synthesis

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon examining the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events including Stevens–Johnson syndrome and Toxic epidermal necrolysis). New results from an exemplar study on shared precipitating and perpetuating inner causes with other related disease phenotypes including aphtous stomatitis, Behçets, erythema multiforme, Hashimoto’s thyroiditis, pemphigus, periodic fevers, Sweet’s syndrome and drug-induced multisystem hypersensitivity are presented. A call for a collaborative, wider demographic profiling and deeper immunotyping in suggested future work is made.

The structure of HLA-DR52c: comparison to other HLA-DRB3 alleles

Class II major histocompatibility complex (MHCII) molecules present antigens to CD4(+) T cells. In addition to the most commonly studied human MHCII isotype, HLA-DR, whose beta chain is encoded by the HLA-DRB1 locus, several other isotypes that use the same alpha chain but have beta chains encoded by other genes. These other DR molecules also are expressed in antigen-presenting cells and are known to participate in peptide presentation to T cells and to be recognized as alloantigens by other T cells. Like some of the HLA-DRB1 alleles, several of these alternate DR molecules have been associated with specific autoimmune diseases and T cell hypersensitivity. Here we present the structure of an HLA-DR molecule (DR52c) containing one of these alternate beta chains (HLA-DRB3*0301) bound to a self-peptide derived from the Tu elongation factor. The molecule shares structurally conserved elements with other MHC class II molecules but has some unique features in the peptide-binding groove. Comparison of the three major HLA-DBR3 alleles (DR52a, b, and c) suggests that they were derived from one another by recombination events that scrambled the four major peptide-binding pockets at peptide positions 1, 4, 6, and 9 but left virtually no polymorphisms elsewhere in the molecules.

Intraocular inflammation in autoimmune diseases

BACKGROUND

The uveal tract represents the vascular organ of the eye. In addition to providing most of the blood supply to the intraocular structures, it acts as a conduit for immune cells, particularly lymphocytes, to enter the eye. Consequently, the uveal tract is represented in many intraocular inflammatory processes. Uveitis is probably a misnomer unless antigens within the uvea are the direct targets of the inflammatory process. A better term of the condition is "intraocular inflammation" (IOI).

OBJECTIVES

To review the presence of IOI in autoimmune diseases, the immunopathogenic mechanisms leading to disease, and treatment.

METHODS

We reviewed the English medical literature by using MEDLINE (1984-2003) employing the terms "uveitis," "intraocular inflammation," and "autoimmune diseases."

RESULTS

An underlying autoimmune disease was identified in up to 40% of patients with IOI, and included spondyloarthropathies, Behcets disease, sarcoidosis, juvenile chronic arthritis, Vogt-Koyanagi-Harada syndrome (an inflammatory syndrome including uveitis with dermatologic and neurologic manifestations), immune recovery syndrome, and uveitis with tubulointerstitial disease. The immunopathogenesis of IOI involves enhanced T-cell response. Recently, guidelines for the use of immunosuppressive drugs for inflammatory eye disease were established and include: corticosteroids, azathioprine, methotrexate, mycophenolate mofetil, cyclosporine, tacrolimus, cyclophosphamide, and chlorambucil. New therapies with limited experience include the tumor necrosis factor alpha inhibitors, interferon alfa, monoclonal antibodies against lymphocyte surface antigens, intravenous immunoglobulin (IVIG), and the intraocular delivery of immunosuppressive agents.

CONCLUSION

An underlying autoimmune disease was identified in up to 40% of patients with IOI. Immunosuppressive drugs, biologic agents, and IVIG are employed for the treatment of IOI in autoimmune diseases.

Visual loss in sarcoid-related uveitis

PURPOSE

To assess the visual acuity outcome after treatment, in patients with differing types of uveitis associated with sarcoidosis, and to determine the types of sight-threatening complications.

METHODS

This was an retrospective, non-comparative, interventional study of patients who had uveitis with a confirmed diagnosis of sarcoidosis and a minimum follow-up duration of 6 months from presentation. The worst affected eye at presentation was selected for the study. Complications causing impaired vision were documented, changes in visual acuity after completion of treatment were measured, and the risk of 'poor outcome' (visual acuity 6/12 and less) was compared in the various types of uveitis, using 'exact' multiple logistic regression to control confounding by other prognostic factors.

RESULTS

Seventy-five patients were studied. The spectrum of ocular inflammation in sarcoidosis is wide. Presentation may be acute and non-granulomatous or chronic and granulomatous with posterior segment involvement being varied. Poor visual outcome was significantly more frequent in multifocal choroiditis (5/7, 71.4%), and in panuveitis without multifocal choroiditis (13/28, 46.4%), compared to only 3/24 (12.5%) patients with anterior uveitis. The excess risks remained significant after adjustment for confounding effects of other prognostic factors including age, sex and manifest systemic sarcoidosis. Causes of visual loss were cataract, glaucoma, macular oedema, vitreous haemorrhage and retinal detachment.

CONCLUSION

Multifocal choroiditis is a less common manifestation of uveitis associated with sarcoidosis but appears to be associated with a worse visual prognosis despite immunosuppressive therapy.

The influence of T cell receptor and cytokine genes on sarcoidosis susceptibility in African Americans

The pathogenesis of sarcoidosis, a multisystem granulomatous disorder, is mediated through immunoregulatory pathways. While sarcoidosis clusters in families, inherited risk factors remain undefined. In search of possible sarcoidosis susceptibility genes, we examined anonymous polymorphic genetic markers tightly linked to six different candidate gene regions on chromosomes 2q13, 5q31, 6p23-25, 7p14-15, 14q11 and 22q11. These candidate regions contain T cell receptor, interleukin (IL) and interferon regulatory factor (IRF) genes. Our study population consisted of 105 African-American sarcoidosis cases and 95 unrelated healthy controls. The allelic frequency distribution of two out of the six markers, IL-1 alpha marker (p = 0.010) on 2q13 and the F13A marker (p = 0.0006) on 6p23-25, was statistically significantly different in cases compared with controls. The two alleles most strongly associated with sarcoidosis were IL-1 alpha*137 (Odds Ratio (OR) = 2.60; 95% confidence interval (CI) = 1.36-4.98) and F13A*188 (OR = 2.42; 95% CI = 1.37-4.30). Individuals that had both of these alleles were at a six-fold increased risk for sarcoidosis (OR = 6.19; 95% CI = 2.54-15.10). Restricting the analysis to cases with at least one first or second-degree relative affected with sarcoidosis increased the OR to 15.38. IL-1 levels are elevated in sarcoidosis and the F13A marker is tightly linked to a gene that codes for a newly identified interferon regulatory factor protein (IRF-4), which is thought to play a role in T cell effector functions. Our results suggest genetic susceptibility to sarcoidosis may be conferred by more than one immune-related gene that act synergistically on disease risk.

Genetic influences on sarcoidosis

To investigate the genetic influences underlying the development of sarcoidosis, HLA class II genotyping was performed in Japanese patients with sarcoidosis and healthy controls using the PCR-RFLP method. The frequencies of both DR52 group antigen-associated alleles (HLA-DRB1*11, -DRB1*12 and -DRB1*14) and DRB1*08 alleles were higher in the patient group, suggesting that the common, specific amino acid residue on the DRB1 molecule of these alleles may determine susceptibility to sarcoidosis. Alternatively, it is possible that another susceptibility gene, linked to these DRB1 alleles, exists within the MHC region. We screened the TNFA, TNFB, HSP70-1 and Hum70t genes around the class III region, as well as the HLA-DMA and -DMB genes in the class II region, for genetic polymorphism in sarcoidosis. None of these genes suggested a susceptibility to sarcoidosis. These studies support the thesis that one of the major genetic factors controlling the development of sarcoidosis is located within the DRB1 locus in the HLA class II region.