Enrichment of Scleroderma Vascular Disease–Associated Autoantigens in Endothelial Lineage Cells

Objective: Scleroderma patients with autoantibodies to CENPs and/or interferon-inducible protein 16 (IFI-16) are at increased risk of severe vascular complications. This study was undertaken to determine whether these autoantigens are enriched in cells of the vasculature. Methods: Successive stages of embryoid bodies (EBs) as well as vascular progenitors were used to evaluate the expression of scleroderma autoantigens IFI-16 and CENP by immunoblotting. CD31 was included to mark early blood vessels. IFI-16 and CD31 expression were defined in paraffin-embedded skin sections from scleroderma patients and from healthy controls. IFI-16 expression was determined by flow cytometric analysis in circulating endothelial cells (CECs) and circulating hematopoietic progenitor cells. Results: Expression of CENP-A, IFI-16, and CD31 was enriched in EBs on days 10 and 12 of differentiation, and particularly in cultures enriched in vascular progenitors (IFI-16, CD31, and CENPs A and B). This pattern was distinct from that of comparator autoantigens. Immunohistochemical staining of paraffin-embedded skin sections showed enrichment of IFI-16 in CD31-positive vascular endothelial cells in biopsy specimens from scleroderma patients and normal controls. Flow cytometric analysis revealed IFI-16 expression in circulating hematopoietic progenitor cells but minimal expression in CECs. Conclusion: Our findings indicate that expression of the scleroderma autoantigens IFI-16 and CENPs, which are associated with severe vascular disease, is increased in vascular progenitors and mature endothelial cells. High level, lineage-enriched expression of autoantigens may explain the striking association between clinical phenotypes and the immune targeting of specific autoantigens.