Autoantigen microarrays reveal myelin basic protein autoantibodies in morphea.

BACKGROUND: Morphea is an autoimmune, sclerosing skin disorder. Despite the recent emphasis on immune dysregulation in morphea, the role of autoantibodies in morphea pathogenesis or utility as biomarkers are poorly defined. METHODS: Autoantigen microarray was used to profile autoantibodies from the serum of participants from the Morphea in Adults and Children (MAC) cohort. Clinical and demographic features of morphea patients with myelin basic protein (MBP) autoantibodies were compared to those without. MBP immunohistochemistry staining was subsequently performed in morphea skin to assess for perineural inflammation in areas of staining. Immunofluorescence staining on mouse brain tissue was also performed using patient sera and mouse anti-myelin basic protein antibody to confirm the presence of MBP antibodies in patient sera. RESULTS: Myelin basic protein autoantibodies were found in greater frequency in morphea (n = 50, 71.4%) compared to systemic sclerosis (n = 2, 6.7%) and healthy controls (n = 7, 20%). Patients with MBP antibodies reported pain at higher frequencies. Morphea skin biopsies, highlighted by immunohistochemistry, demonstrated increased perineural inflammation in areas of MBP expression. Immunofluorescence staining revealed an increased fluorescence signal in myelinated areas of mouse brain tissue (i.e. axons) when incubated with sera from MBP antibody-positive morphea patients compared to sera from MBP antibody-negative morphea patients. Epitope mapping revealed target epitopes for MBP autoantibodies in morphea are distinct from those reported in MS, and included fragments 11-30, 41-60, 51-70, and 91-110. CONCLUSIONS: A molecular classification of morphea based on distinct autoantibody biosignatures may be used to differentially classify morphea. We have identified anti-MBP as a potential antibody associated with morphea due to its increased expression in morphea compared to healthy controls and systemic sclerosis patients.

Transcriptional and Cytokine Profiles Identify CXCL9 as a Biomarker of Disease Activity in Morphea.

IFN-related pathways have not been studied in morphea, and biomarkers are needed. We sought to characterize morphea serum cytokine imbalance and IFN-related gene expression in blood and skin to address this gap by performing a case-control study of 87 participants with morphea and 26 healthy control subjects. We used multiplexed immunoassays to determine serum cytokine concentrations, performed transcriptional profiling of whole blood and lesional morphea skin, and used double-staining immunohistochemistry to determine the cutaneous cellular source of CXCL9. We found that CXCL9 was present at increased concentrations in morphea serum (P < 0.0001), as were other T helper type 1 cytokines. CXCL9 serum concentration correlated with the modified Localized Scleroderma Skin Severity Index (r = 0.44, P = 0.0001), a validated measure of disease activity. CXCL9 gene expression was also increased in inflammatory lesional morphea skin (fold change = 30.6, P = 0.006), and preliminary transcriptional profiling showed little evidence for IFN signature in whole blood. Double-staining immunohistochemistry showed CXCL9 co-localized with CD68+ dermal macrophages. In summary, inflammatory morphea is characterized by T helper type 1 cytokine imbalance in serum, particularly CXCL9, which is associated with disease activity. CXCL9 expression in lesional macrophages implicates the skin as the source of circulating cytokines. CXCL9 is a promising biomarker of disease activity in morphea.