Background/Purpose:

System Lupus Erythematosus (SLE) is an autoimmune disease that is over-represented in the American Indian (AI) population and often manifests as a more severe disease. Although the clinical manifestations can be diverse, nearly all patients share the presence of autoantibodies, including anti-dsDNA and anti-Sm which have high specificity for the disease. American Indian SLE patients often lack reactivity to autoantigens commonly found in SLE patients of other ethnicities. We have observed that sera from 41% of AI SLE patients contain unidentified autoantigenic reactivity by precipitin testing compared to 24% for AA, 17% for EA, and 23% for HA. Therefore the goal of this study is to identify non-traditional autoantibody specificities associated with disease in AI SLE patients.

Methods:

The sera from 100 AI SLE patients, 37 AI unaffected controls, 16 AI unaffected family members, and 17 AI patients with other systemic autoimmune diseases were screened using a 128 autoantigen protein array. Antigen reactivity based on a mean fluorescence intensity three standard deviations above the average of the unaffected negative controls for that antigen were considered positive. Hierarchical clustering of these data was used to identify shared autoantibody reactivities.

Results:

Twenty-two percent (n=22) of all of the positive SLE patients, 19% (n=3) of all positive unaffected family members, and 24% (n=4) of all positive other autoimmune disease samples had reactivity to the M2 mitochondrial antigen typically associated with primary biliary cirrhosis (PBC), an autoimmune liver disease. Furthermore, 91% (n=20) of the M2 positive SLE samples also contained 1 or more autoantibodies specific for or associated with myositis, whereas only 33% (n=1) of M2 positive unaffected family member samples, and 50% (n=2) of the M2 positive samples from individuals with other autoimmune disease contained myositis specific or associated autoantibodies.

Conclusion:

This study suggests that M2 and myositis autoantibodies are associated with disease in American Indian SLE patients. Although SLE patients are often diagnosed with more than one autoimmune disease, the coexistence of SLE and PBC or myositis is rare. The study was funded in part by Native American Research Centers for Health.

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/characterization-of-unexpected-autoantibody-specificities-in-american-indian-sle-patients/