The genetics of primary Sjögren's syndrome

Association between systemic lupus erythematosus and myasthenia gravis: A population-based National Study

BACKGROUND

Systemic lupus erythematosus (SLE) and myasthenia gravis (MG) are autoimmune diseases. Previous case reports and case series suggest an association may exist between these diseases, as well as an increased risk of SLE after thymectomy for MG. We undertook this study to determine whether SLE and MG were associated in large cohorts.

METHODS

We searched the IBM Watson Health Explorys platform and the Department of Veterans Affairs Million Veteran Program (MVP) database for diagnoses of SLE and MG. In addition, we examined subjects enrolled in the Lupus Family Registry and Repository (LFRR) as well as controls for a diagnosis of MG.

RESULTS

Among 59,780,210 individuals captured in Explorys, there were 25,750 with MG and 65,370 with SLE. 370 subjects had both. Those with MG were >10 times more likely to have SLE than those without MG. Those with both diseases were more likely to be women, African American, and at a younger age than MG subjects without SLE. In addition, the MG patients who underwent thymectomy had an increased risk of SLE compared to MG patients who had not undergone thymectomy (OR 3.11, 95% CI: 2.12 to 4.55). Autoimmune diseases such as pernicious anemia and miscellaneous comorbidities such as chronic kidney disease were significantly more common in MG patients who developed SLE. In the MVP, SLE and MG were also significantly associated. Association of SLE and MG in a large SLE cohort with rigorous SLE classification confirmed the association of SLE with MG at a similar level.

CONCLUSION

While the number of patients with both MG and SLE is small, SLE and MG are strongly associated together in very large databases and a large SLE cohort.

Tear ATG5 as a Potential Novel Biomarker in the Diagnosis of Sjögren Syndrome

Autophagy has been suggested to have an important role in the pathogenesis of Sjögren syndrome (SS). We previously identified that autophagy related 5 (ATG5) was elevated in the tear and conjunctival epithelial cells of SS dry eyes (DE) compared to non-SS DE. The purpose of this study was to investigate the role of tear ATG5 as a potential biomarker in the diagnosis of SS. To confirm this hypothesis, we evaluated the tear ATG5 concentration, and other ocular tests (Schirmer I, tear breakup time (TBUT), ocular surface staining (OSS) score, ocular surface disease index (OSDI)) in SS and non-DE, and compared their diagnostic performance to discriminate SS from non-SS DE. Tear ATG5 showed the greatest area under the curve (AUC = 0.984; 95% CI, 0.930 to 0.999) among the tests, and a 94.6% sensitivity and 93.6% specificity at a cutoff value of >4.0 ng/mL/μg. Our data demonstrated that tear ATG5 may be helpful as an ocular biomarker to diagnose and assess SS. In the future, the diagnostic power of tear ATG for SS should be validated.

Functional characterization of the MECP2/IRAK1 lupus risk haplotype in human T cells and a human MECP2 transgenic mouse

Genetic polymorphism in MECP2/IRAK1 on chromosome Xq28 is a confirmed and replicated susceptibility locus for lupus. High linkage disequilibrium in this locus suggests that both MECP2 and IRAK1 are candidate genes for the disease. DNA methylation changes in lupus T cells play a central role in the pathogenesis of lupus, and MeCp-2 (encoded by MECP2) is a master regulator of gene expression and is also known to recruit DNA methyltransferase 1 (DNMT1) during DNA synthesis. Using human T cells from normal individuals with either the lupus risk or the lupus protective haplotype in MECP2/IRAK1, we demonstrate that polymorphism in this locus increases MECP2 isoform 2 mRNA expression in stimulated but not unstimulated T cells. By assessing DNA methylation levels across over 485,000 methylation sites across the entire genome, we further demonstrate that the lupus risk variant in this locus is associated with significant DNA methylation changes, including in the HLA-DR and HLA-DQ loci, as well as interferon-related genes such as IFI6, IRF6, and BST2. Further, using a human MECP2 transgenic mouse, we show that overexpression of MECP2 alters gene expression in stimulated T cells. This includes overexpression of Eif2c2 that regulates the expression of multiple microRNAs (such as miR-21), and the histone demethylase Jhdm1d. In addition, we show that MECP2 transgenic mice develop antinuclear antibodies. Our data suggest that the lupus-associated variant in the MECP2/IRAK1 locus has the potential to affect all 3 epigenetic mechanisms: DNA methylation, microRNA expression, and histone modification. Importantly, these data support the notion that variants within the MECP2 gene can alter DNA methylation in other genetic loci including the HLA and interferon-regulated genes, thereby providing evidence for genetic-epigenetic interaction in lupus.

Epigallocatechin-3-gallate modulates antioxidant and DNA repair-related proteins in exocrine glands of a primary Sjogren's syndrome mouse model prior to disease onset

The autoimmune disorder primary Sjogren's syndrome (SS) is associated with xerostomia and xerophthalmia. SS pathogenesis involves both genetic/epigenetic and environmental factors. A major potential contributor is oxidative stress associated with damage to cellular components, including DNA. We reported previously that the green tea polyphenol epigallocatechin-3-gallate (EGCG) normalizes the elevated levels of proliferating cell nuclear antigen (PCNA), a key component of DNA repair, in the NOD mouse model for SS and type 1 diabetes. The current study examined levels of the antioxidant enzymes peroxiredoxin 6 (PRDX6), catalase and superoxide dismutase (SOD), as well as PCNA, in NOD.B10.Sn-H2 mice, a model for primary SS, and determined the effect of EGCG on their expression. PCNA elevation was detected in the submandibular gland and pancreas by 8 weeks of age in water-fed mice, and increased through 14 weeks of age, prior to overt onset of symptoms. This early PCNA elevation was followed by a decline of peroxiredoxin 6 protein. In contrast, EGCG-fed mice exhibited normal levels of PCNA and peroxiredoxin 6, comparable to healthy untreated BALB/c mice. Similar patterns were observed in the pancreas, even though these mice do not develop diabetes. Thus, elevated PCNA is an early biomarker for exocrine glandular dysfunction associated with SS-like autoimmune disease, accompanied subsequently by decreased PRDX6 antioxidant enzyme levels that could further contribute to oxidative stress, and these changes precede inflammatory cell infiltration. Importantly, EGCG consumption normalizes the expression of these biomarkers in this model. These observations could lead to early diagnosis and intervention of autoimmune disorders.

Effects of oral consumption of the green tea polyphenol EGCG in a murine model for human Sjogren's syndrome, an autoimmune disease

SIGNIFICANCE

Protection of glandular cells from autoimmune-induced damage would be of significant clinical benefit to Sjogren's syndrome (SS) patients. Epigallocatechin-3-gallate (EGCG) possesses anti-apoptotic, anti-inflammatory, and autoantigen-inhibitory properties.

AIMS

To investigate if EGCG protects against certain autoimmune-induced pathological changes in the salivary glands of the non-obese diabetic (NOD) mouse model for SS.

MAIN METHODS

Animals were provided with either water or water containing 0.2% EGCG. At the age of 8, 16 and 22 weeks, submandibular salivary gland tissue and serum samples were collected for pathological and serological analysis.

KEY FINDINGS

Significant lymphocyte infiltration was observed in the salivary glands of the water-fed group at the age of 16 weeks, while the EGCG group showed reduced lymphocyte infiltration. By 22 weeks of age, water-fed animals demonstrated elevated levels of apoptotic activity within the lymphocytic infiltrates, and high levels of serum total anti-nuclear antibody, compared to EGCG-fed animals. Remarkably, proliferating cell nuclear antigen (PCNA) and Ki-67 levels in the salivary glands of water-fed NOD mice were significantly elevated in comparison to BALB/c control mice; in contrast, PCNA and Ki-67 levels in EGCG-fed NOD animals were similar to BALB/c mice. These results indicate that EGCG protects the NOD mouse submandibular glands from autoimmune-induced inflammation, and reduces serum autoantibody levels. Abnormal proliferation, rather than apoptosis, appears to be a characteristic of the NOD mouse gland that is normalized by EGCG. The evidence suggests that EGCG could be useful in delaying or managing SS-like autoimmune disorders.

Polymorphism in the 5' regulatory region of the B-lymphocyte activating factor gene is associated with the Ro/La autoantibody response and serum BAFF levels in primary Sjogren's syndrome

OBJECTIVE

To investigate the association between haplotypes in the 5' regulatory region of the B-lymphocyte activating factor (BAFF) gene, disease susceptibility and serum BAFF (s-BAFF) levels in Caucasian primary SS (pSS) patients.

METHODS

Case-control study in an established pSS cohort with PCR-RFLP genotyping for four SNPs (-2841 T-->C, -2704 T-->C, -2701 T-->A, -871 C-->T), which tag a haplotype block in the 5' regulatory region of the BAFF gene and s-BAFF determination by ELISA.

RESULTS

s-BAFF levels were elevated in Ro/La-positive pSS patients (n = 85, 1770 pg/ml) compared with both Ro/La-negative pSS patients (n = 27, 1193 pg/ml) and controls (n = 59, 1171 pg/ml), P < 0.001. s-BAFF increased with diversification of the anti-Ro/La antibody response, but was not correlated with age, RF or immunoglobulin G levels. There were four common BAFF haplotypes. While the CTAT haplotype was associated with Ro/La-positive pSS [odds ratio (OR) 2.6; 95% CI 1.7, 4.1; P = 0.00004], the TTTT haplotype was associated with elevated s-BAFF in autoantibody-positive pSS (n = 85; 88% females; P = 0.008). The shared -871 T allele had no independent contribution to disease susceptibility or s-BAFF.

CONCLUSIONS

Disease susceptibility for Ro/La-positive pSS is increased with the CTAT haplotype, but not associated with high s-BAFF levels. Elevated s-BAFF levels in pSS are associated with the TTTT haplotype and may be a secondary phenomenon in Ro/La-positive pSS. While both haplotypes carry the -871 T allele, this allele is not independently associated with disease susceptibility.

Self-reported dry eyes and diabetic history

PURPOSE

Dry eyes and diabetes have been linked in previous studies. However, the connection between a family history of diabetes and self-reported dry eyes needs to be explored. Patients with self-reported dry eyes were screened for self-reported diabetes or a family history of diabetes.

METHODS

A total of 392 patients were given a simple questionnaire about diabetic history and asked to categorize their level of discomfort owing to ocular dryness as none, trace, mild, moderate, or severe (scored as 0 to 4).

RESULTS

A total of 34.4% (135 of 392) of the sample had some self-reported symptom of dryness, 29.8% (117 of 392) could be considered clinically relevant (mild, moderate or severe), 7.4% (29 of 392) reported that they had diabetes, and 35.7% (140 of 392) reported a positive family history for diabetes. A total of 52.9% of those with either diabetes or borderline diabetes had self-reported clinically relevant dry eyes. A total of 35.7% of those patients with a family history of diabetes and 25.6% with no family history had self-reported clinically relevant dry eyes. The patients-with-diabetes group had a median dryness score of 2 (mild) and nondiabetics had a score of 0 (none). For both those with a diabetic family history and for those with no history of diabetes, the median dryness score was 0 (none). However, the dryness score distributions for those patients with a family history of diabetes and those patients with no family history of diabetes were significantly different (P = 0.031); those with a family history tended to have higher dryness scores. The distributions of dryness scores of the diabetic and nondiabetic groups were also significantly different (P = 0.0076).

CONCLUSIONS

Patients in this study who self-reported diabetes were found to have higher levels of dryness than those without diabetes. Patients with a family history of diabetes also had a greater tendency to report dry eyes in this cohort. These results are consistent with earlier reports of a link between diabetes and dry eye disease and identify diabetes as another aspect of family history that may be relevant to risk for dry eyes.

Pathophysiology of Sjögren's syndrome

The term Sjögren's syndrome refers to keratoconjunctivitis sicca and xerostomia due to lymphocytic infiltrates of lachrymal and salivary glands. The current used criteria for diagnosis of primary Sjögren's syndrome is the American-European consensus. Primary Sjögren's syndrome is an autoimmune disorder characterized by lymphocytic infiltrates and destruction of the salivary and lachrymal glands and systemic production of autoantibodies to the ribonucleoprotein particles SS-A/Ro and SS-B/La. The infiltrating cells (T- and B-cells, dendritic cells) interfere with glandular function at several points: destruction of glandular elements by cell-mediated mechanisms; secretion of cytokines that activate pathways bearing the signature of type 1 and 2 interferons; production of autoantibodies that interfere with muscarinic receptors; and secretion of metalloproteinases (MMPs) that interfere with the interaction of the glandular cell with its extracellular matrix, which is necessary for efficient glandular function. As the process progresses, the mucosal surfaces become sites of chronic inflammation and the start of a vicious circle. Despite extensive study of the underlying cause of Sjögren's syndrome, the pathogenesis remains obscure. In broad terms, pathogenesis is multifactorial; environmental factors are thought to trigger inflammation in individuals with a genetic predisposition to the disorder.

Sjögren's syndrome in dermatology

Sjogren's Syndrome (SS) is a systemic autoimmune disease characterized by dry eyes (keratoconjunctivis sicca) and dry mouth (xerostomia). To fulfill diagnostic criteria, patients must have objective signs of dryness on examination and laboratory confirmation of an autoimmune process as evidenced by a positive autoantibody to SS-A antigen or a characteristic lip biopsy. SS may exist as a primary condition or in association with other systemic autoimmune disorders (termed secondary SS) such as rheumatoid arthritis, systemic lupus erythematous (SLE), progressive systemic sclerosis (scleroderma), or dermatomyositis. Exclusions to the diagnosis include pre-existing lymphoma, hepatitis C or HIV infection. Pathogenesis involves both genetic (especially HLA-DR) and environmental factors. Both T-cells and B-cells are involved in the generation of cytokines and chemokines within the glands. The epithelial cells of the glands also play a role in pathogenesis. The dermatologic manifestations range from drynessness (sicca) and its complications to vasculitis. There is a significant overlap in the clinical manifestations, as well as treatment, of SS and SLE. However, SS patients require special attention to the complications of ocular dryness (keratocojunctivitis sicca and blepharitis) and oral dryness (rapid tooth loss and oral candidiasis) SS patients have a markedly increased risk of lymphoma and enlarged lymph nodes or persistently enlarged parotid/submandibular glands that require further evaluation.

Clinical, serologic, and genetic profiles of patients with associated Sjögren's syndrome and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS) can coexist in patients. The aim of this study was to investigate the clinical, laboratory, and serologic features of the association of the two diseases. Data from 56 patients having both SS and SLE were analyzed, with special emphasis on their clinical, laboratory, and serologic features. Data from 50 patients with SLE and 50 patients with SS served as control subjects. The mean age in SS-SLE group was lower than in patients with SS but higher than patients with SLE. When SLE and SS were associated, presence of rheumatoid factor was less frequent, whereas anti-Ro/SS-A, anti-La/SS-B, antinuclear, anti-DNA, and antiphospholipid autoantibodies appeared more often. Antiphospholipid syndrome, anemia, leucopenia, and lymphopenia were more frequent in the associated disease than in patients with SS alone. In SS-SLE patients, pulmonary, renal, skin, central nervous system involvement, and serositis occurred more often than in patients with SS alone. Thyroiditis, autoantibodies to Ro/SS-A, La/SS-B and ds-DNA was more frequent in the SS-SLE group than in patients with SLE. Genetic background of the patients did not differ significantly. In conclusion, characteristic clinical, laboratory and serologic features distinguish between the association of SS and SLE and the primary forms of these two diseases.

A New Approach to Managing Oral Manifestations of Sjogren's Syndrome and Skin Manifestations of Lupus

Sjogren's syndrome (SS) is an autoimmune disorder that affects the salivary glands, leading to xerostomia, and the lacrimal glands, resulting in xerophthalmia. Secondary SS is associated with other autoimmune disorders such as systemic rheumatic diseases and systemic lupus erythematosis (SLE), which can affect multiple organs, including the epidermis. Recent studies have demonstrated that green tea polyphenols (GTPs) possess both anti-inflammatory and anti-apoptotic properties in normal human cells. Epidemiological evidence has indicated that, in comparison to the United States, the incidence of SS, clinical xerostomia and lupus is considerably lower in China and Japan, the two leading green tea-consuming countries.Thus, GTPs might be responsible, in part, for geographical differences in the incidence of xerostomia by reducing the initiation or severity of SS and lupus. Consistent with this, molecular, cellular and animal studies indicate that GTPs could provide protective effects against autoimmune reactions in salivary glands and skin. Therefore, salivary tissues and epidermal keratinocytes could be primary targets for novel therapies using GTPs. This review article evaluates the currently available research data on GTPs, focusing on their potential application in the treatment of the oral manifestations of SS and skin manifestations of SLE.

Mechanisms dependent on tryptophan catabolism regulate immune responses in primary Sjögren's syndrome

To investigate the possible role of tryptophan metabolism in immune regulation of primary Sjögren's syndrome (pSS) the serum concentrations of tryptophan and its metabolite kynurenine were measured by reverse-phase high-performance liquid chromatography (HPLC) in 103 patients with pSS, 56 patients with sicca symptoms and 309 healthy blood donors. The kynurenine per tryptophan ratio (kyn/trp), which reflects the activity of the indoleamine-pyrrole 2,3-dioxygenase (IDO) enzyme involved in tryptophan catabolism, was calculated. Both female and male patients with pSS had significantly higher serum kynurenine concentrations and kyn/trp than subjects with sicca symptoms or healthy blood donors. The median (quartile range) concentration of kynurenine in female patients with pSS was 2.41 micromol/l (1.86-3.26) compared with 1.85 micromol/l (1.58-2.38, P < 0.0001) in subjects with sicca symptoms and 1.96 micromol/l (1.65-2.27, P < 0.0001) in healthy blood donors. Their kyn/trp x 1000 was 34.0 (25.1-44.3) compared with 25.3 (21.1-31.5, P < 0.0001) in subjects with sicca symptoms and 24.3 (21.0-28.9, P < 0.0001) in healthy blood donors. Female pSS patients with high IDO activity (kyn/trp x 1000 > or = 34.0) had significantly higher ESR, serum C-reactive protein, serum IgA and serum beta-2 microglobulin concentrations as well as higher serum creatinine levels, and they had positive antinuclear antibodies more frequently and presented with more American-European consensus group criteria than those with low IDO activity (kyn/trp x 1000 < 34.0). These data suggest that mechanisms dependent on tryptophan catabolism regulate immune responses in pSS. Tryptophan degradation is enhanced in patients with pSS, and high IDO activity is associated with severity of pSS.

A comparability study of the emerging protein array platforms with established ELISA procedures

Recent developments in microarray technology have made it possible to perform immunoassays in a multiplexed format. This ability is highly desirable given the potential for greater throughput analysis. In spite of the obvious advantages, a number of issues arise as a result of multiplexing the reactions. In this study, we have assessed the performance characteristics that are associated with the transfer of technology from a uniplexed to a multiplexed format. Two solution phase array platforms were chosen for this study: the commercially available Luminex(100) xMap system (Austin, Texas, USA) and the UltraPlex technology devised by SmartBead Technologies Ltd. (Cambridge, UK). For this comparative study, a test for the presence of six autoantibodies in a selection of human patient serum samples was chosen as a model system. The multiplexed Luminex xMap and SmartBead UltraPlex assays were generally comparable. However, both systems generated some results that were at variance with those obtained by ELISA. The different methods used for the assignment of the cut-off levels for each of the assays within any given platform was identified as the major source of these non-concordant results. The present study demonstrates that array platforms have the potential to be used in immunodiagnostics providing that suitable cut-off levels are established.

Th2 cytokine genotypes are associated with a milder form of primary Sjogren's syndrome

BACKGROUND

Immunohistological studies on salivary and lacrimal glands have yielded conflicting results on the Th1/Th2 balance in primary Sjögren's syndrome (pSS).

OBJECTIVE

To establish whether pSS is a Th1 or Th2 directed autoimmune disease by analysing the polymorphism of the genes encoding for cytokines involved in the regulation of Th1/Th2 differentiation.

METHODS

The polymorphisms of the genes encoding for interleukin 4 (IL4) -590 C/T, interleukin 13 (IL13) +2044 G/A, and interferon gamma (IFNG) +874 T/A were analysed in 63 white Finnish patients with pSS (61 female, two male) and in 63 healthy controls. The clinical and immunological data on the pSS patients were analysed in relation to these cytokine gene polymorphisms.

RESULTS

There were no significant differences in the genotype or allele frequencies of IL4 -590, IL13 +2044, or IFNG +874 between pSS patients and controls. The erythrocyte sedimentation rate and concentrations of serum IgA and serum beta2 microglobulin were lower in pSS patients carrying the IL4 -590 T allele or the IL13 +2044 A allele than in those not carrying the respective alleles. The IL4 -509 T allele and IL13 +2044 A allele carriers less often had purpura than the corresponding non-carriers.

CONCLUSIONS

The frequencies of the cytokine genotypes regulating Th1/Th2 differentiation did not differ between pSS patients and controls. However, the presence of cytokine genotypes with increased susceptibility to atopic and other Th2 diseases was associated with signs of a milder form of pSS. This finding would favour a hypothesis envisaging pSS as primarily a Th1 mediated autoimmune disease.

Inhibition of autoantigen expression by (-)-epigallocatechin-3-gallate (the major constituent of green tea) in normal human cells

Autoimmune disorders, characterized by inflammation and apoptosis of target cells leading to tissue destruction, are mediated in part by autoantibodies against normal cellular components (autoantigens) that may be overexpressed. For example, antibodies against the autoantigens SS-A/Ro and SS-B/La are primary markers for systemic lupus erythematosus and Sjögren's syndrome. Recently, studies in animals demonstrated that green tea consumption may reduce the severity of some autoimmune disorders, but the mechanism is unclear. Herein, we sought to determine whether the most abundant green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), affects autoantigen expression in human cells. Cultures of pooled normal human primary epidermal keratinocytes and of an immortalized human salivary acinar cell line were incubated with 100 microM EGCG (a physiologically achievable level for topical application or oral administration) for various time periods and then analyzed by cDNA microarray analysis, reverse transcription-polymerase chain reaction, and Western blotting for expression of several major autoantigen candidates. EGCG inhibited the transcription and translation of major autoantigens, including SS-B/La, SS-A/Ro, coilin, DNA topoisomerase I, and alpha-fodrin. These findings, taken together with green tea's anti-inflammatory and antiapoptotic effects, suggest that green tea polyphenols could serve as an important component in novel approaches to combat autoimmune disorders in humans.

Sjögren's syndrome

Sjögren's syndrome is a chronic autoimmune disorder of the exocrine glands with associated lymphocytic infiltrates of the affected glands. Dryness of the mouth and eyes results from involvement of the salivary and lacrimal glands. The accessibility of these glands to biopsy enables study of the molecular biology of a tissue-specific autoimmune process. The exocrinopathy can be encountered alone (primary Sjögren's syndrome) or in the presence of another autoimmune disorder such as rheumatoid arthritis, systemic lupus erythematosus, or progressive systemic sclerosis. A new international consensus for diagnosis requires objective signs and symptoms of dryness including a characteristic appearance of a biopsy sample from a minor salivary gland or autoantibody such as anti-SS-A. Exclusions to the diagnosis include infections with HIV, human T-lymphotropic virus type I, or hepatitis C virus. Therapy includes topical agents to improve moisture and decrease inflammation. Systemic therapy includes steroidal and non-steroidal anti-inflammatory agents, disease-modifying agents, and cytotoxic agents to address the extraglandular manifestations involving skin, lung, heart, kidneys, and nervous system (peripheral and central) and haematological and lymphoproliferative disorders. The most difficult challenge in diagnosis and therapy is patients with symptoms of fibromyalgia (arthralgia, myalgia, fatigue) and oral and ocular dryness in the presence of circulating antinuclear antibodies.

Homozygosity for the 168His variantof the minor histocompatibility antigen HA-1is associated with reduced riskof primary Sjögren's syndrome

The genes for the human ATP-binding cassette (ABC) transporter ABCA7 and the minor histocompatibility antigen HA-1 are juxtaposed in close proximity on chromosome 19p13.3. The multispan transmembrane protein ABCA7 contains an extracellular domain that is recognized by antisera from patients with Sjögren's syndrome ("Sjögren-epitope"). Recent work from our laboratory demonstrating the involvement of ABCA7 in cellular ceramide and phosphatidylserine export suggests a role for this transporter in programmed cell death. In HA-1, a protein of unknown function, a His/Arg polymorphism (His168Arg), which constitutes the immunologic target for HA-1-specific cytotoxic T cells, has been causatively linked to graft-versus-host disease after allogeneic stem cell transplantation. Because these findings suggest a potential implication of ABCA7 and HA-1 in immune processes, we tested the hypothesis that allelic variants in both genes are associated with autoimmune disorders. We identified a total of 31 exonic single-nucleotide polymorphisms (SNP) in the ABCA7/HA-1 gene complex, nine of which represent non-synonymous nucleotide alterations. Genotypes of ABCA7 and HA-1 SNP were determined in three distinct Caucasian populations of patients with primary Sjögren's syndrome and ethnically matched controls. Comparison of allele frequencies between these groups revealed that the incidence of the HA-1 168His allele is significantly lower in Sjögren's syndrome patients than in controls (p<0.003). In contrast, the frequencies of all ABCA7 allelic variants and additional HA-1 polymorphisms were similar in patients and controls. In cohorts of patients with systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis, no significant differences in the frequencies of ABCA7 and HA-1 allelic variants were observed relative to controls. Our results suggest that the HA-1 168His variant is associated with reduced susceptibility to primary Sjögren's syndrome.