Role of HLA-DR antigens in Japanese patients with sarcoidosis

Association of serum TNF-α, IL-8 and free light chain with HLA-DR B alleles expression in pulmonary and extra-pulmonary sarcoidosis

Background

Sarcoidosis is a systemic disease of unknown etiology characterized histologically by the observation of non-caseating granulomas and several immunological abnormalities. Sarcoidosis is a multi-organ disorder which involves formation of granulomas in many tissues including the lungs (pulmonary) and others such as skin, bone, heart (extra pulmonary). Associations between human leukocyte antigens (HLA), the encoded cell surface receptor (HLA-DR) and sarcoidosis have been reported in several studies. Several HLA-DR alleles have been described as potential risk factors for sarcoidosis in distinct ethnic groups however evidence for a relationship between HLA-DR alleles and pulmonary and extra-pulmonary sarcoidosis (EPS) is still scarce. Although the etiology of the disease remains unclear, infectious and environmental factors have been postulated. Inflammatory cytokines and chemokines may play important roles in the pathogenesis of sarcoidosis and serum free light chain (FLC) numbers have been implicated in several immunologic disorders.

Purpose of the study

The aim of the present study was to investigate HLA associations with serum cytokines and FLC in Iranian patients with pulmonary (n = 86) and EPS (n = 46).

Results

We found that among the 16 HLA DRB alleles only *7 and *12 were different in sarcoidosis patients. The levels of TNF-α and IL-8 in pulmonary sarcoidosis patients were higher than in EPS (P < 0.05) whereas the levels of FLC subunits in EPS were higher than in pulmonary sarcoidosis.

Conclusion

This data may suggests a link between HLA-DRB *12 and sarcoidosis in Iranian population.

HLA-DRB1*1101: a significant risk factor for sarcoidosis in blacks and whites

Sarcoidosis is a granulomatous disorder of unknown etiology, associated with an accumulation of CD4+ T cells and a TH1 immune response. Since previous studies of HLA associations with sarcoidosis were limited by serologic or low-resolution molecular identification, we performed high-resolution typing for the HLA-DPB1, HLA-DQB1, HLA-DRB1, and HLA-DRB3 loci and the presence of the DRB4 or DRB5 locus, to define HLA class II associations with sarcoidosis. A Case Control Etiologic Study of Sarcoidosis (ACCESS) enrolled biopsy-confirmed cases (736 total) from 10 centers in the United States. Seven hundred six (706) controls were case matched for age, race, sex, and geographic area. We studied the first 474 ACCESS patients and case-matched controls. The HLA-DRB1 alleles were differentially distributed between cases and controls (P<.0001). The HLA-DRB1*1101 allele was associated (P<.01) with sarcoidosis in blacks and whites and had a population attributable risk of 16% in blacks and 9% in whites. HLA-DRB1-F(47) was the amino acid residue most associated with sarcoidosis and independently associated with sarcoidosis in whites. The HLA-DPB1 locus also contributed to susceptibility for sarcoidosis and, in contrast to chronic beryllium disease, a non-E(69)-containing allele, HLA-DPB1*0101, conveyed most of the risk. Although significant differences were observed in the distribution of HLA class II alleles between blacks and whites, only HLA-DRB1*1501 was differentially associated with sarcoidosis (P<.003). In addition to being susceptibility markers, HLA class II alleles may be markers for different phenotypes of sarcoidosis (DRB1*0401 for eye in blacks and whites, DRB3 for bone marrow in blacks, and DPB1*0101 for hypercalcemia in whites). These studies confirm a genetic predisposition for sarcoidosis and present evidence for the allelic variation at the HLA-DRB1 locus as a major contributor.

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

BACKGROUND

Susceptibility to the development of sarcoidosis has been demonstrated to be associated with HLA-DR5, -DR6, and -DR8 encoded by the DRB1 gene. However, involvement of the DRB3 (HLA-DR52) gene in the development of sarcoidosis remains unclear.

METHODS

HLA-DRB3 genotyping was performed using the PCR-RFLP method and the clinical features of the patients with and without the DR3, 5, 6, 8 group antigens were compared.

RESULTS

HLA-DRB3 genotyping indicated an association between DRB3*0101 and sarcoidosis. The DR8 haplotype lacking the DRB3 gene has been found to be increased significantly in sarcoidosis, suggesting that the HLA-DRB3 gene is not a primary determinant of predisposition to sarcoidosis. The association of DRB3*0101 with sarcoidosis is attributable to linkage disequilibrium with DR5- and DR6-associated alleles. There were significant decreases in the DR3, 5, 6, 8 group (DR5, DR6, or DR8) antigen frequencies in patients with retinal perivasculitis, high intraocular pressure (or secondary glaucoma), and optic nerve and/or macular lesion. Correlations were observed among the DR3, 5, 6, 8 group antigens, early onset sarcoidosis and disease with fewer intraocular lesions.

CONCLUSION

This established a molecular basis for some of the clinical heterogeneity observed in sarcoidosis.

Analysis of restriction fragment length polymorphism for the HLA-DR gene in Japanese patients with sarcoidosis

BACKGROUND

It is commonly assumed that some immunological disorder may play a part in the pathogenesis of sarcoidosis. Previous studies by several groups have shown a significant association with HLA-DR antigens in patients with sarcoidosis. In this study, restriction fragment length polymorphism (RFLP) analysis of the HLA-DR gene was designed to confirm the association at the gene level and to look for a gene rearrangement which may influence susceptibility to sarcoidosis.

METHODS

Thirty two unrelated Japanese patients with sarcoidosis were tested for HLA antigens and subjected to RFLP analysis after digestion with Eco RI, Pst I, Bam HI, Pvu II, and Hind III by using an HLA-DR beta cDNA probe. A group of 47 unrelated healthy Japanese subjects served as controls. Frequencies of each restriction fragment were compared between the patients and the control subjects. Correlation between fragment frequencies and clinical features were also analysed.

RESULTS

No restriction fragments of HLA-DR beta gene were found specific to the patients with sarcoidosis. The RFLP analysis could detect polymorphism of HLA-DR beta genes that was not distinguishable by conventional serological methods. Several restriction fragments of the DR beta gene were seen only in DRw52 positive individuals, and showed higher frequencies in the patients than in control subjects. The patients with these DNA fragments were likely to have limited stage disease with no ophthalmic involvement.

CONCLUSIONS

An association between HLA and sarcoidosis was noted at the DNA level, although no restriction fragments were specific for this disease. RFLP analysis of the HLA gene is a more useful method than the usual HLA typing, and should be the first step in identifying the gene sequence which is connected with susceptibility to sarcoidosis.