Autoantibodies to mitochondria in systemic sclerosis. frequency and characterization using recombinant cloned autoantigen

David R. Fregeau, Patrick S.C. Leung, Ross L. Coppel, L. Jane Mcneilage, Thomas A. Medsger, M. Eric Gershwin

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Mitochondrial autoantibodies, a hallmark of primary biliary cirrhosis (PBC), have been widely described for many years in patients with systemic sclerosis, and there have been several reports of the concurrence of systemic sclerosis and PBC. However, there is very little information with respect to the significance of these autoantibodies or any definitive evidence that the antigens involved represent the mitochondrial autoantigens (M2 complex) described in PBC. We have cloned and sequenced a rat complementary DNA which encodes for all the epitopes recognized by autoantibodies to the major, or 70‐kd, mitochondrial autoantigen in patients with PBC. Using this recombinant fused autoantigen, as well as by immunoblotting with human placental mitochondria, we tested for antimitochondrial antibody specificity in sera from 250 patients with systemic sclerosis. Nineteen sera (7.6%), including those from patients with CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias) and diffuse scleroderma, had reactivity with human placental mitochondria proteins by immunoblot testing. All 19 sera reacted with the M2 complex. All sera that reacted with the 70‐kd protein likewise reacted with the recombinant cloned autoantigen. The predominant autoantibody isotype to the 70‐kd protein was IgG3. Interestingly, the 70‐kd protein is 11% proline, an amino acid which is frequently preceded by hydrophobic amino acids.

Original languageEnglish
Pages (from-to)386-392
Number of pages7
JournalArthritis & Rheumatism
Issue number3
Publication statusPublished - 1 Jan 1988
Externally publishedYes

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