Enhanced type I interferon gene signature in primary antiphospholipid syndrome: Association with earlier disease onset and preeclampsia.

OBJECTIVE: Recently, two studies demonstrated that a relevant percentage of primary antiphospholipid syndrome (PAPS) patients had an upregulation of interferon (IFN) genes. However, 20%-28% of these patients had anti-dsDNA, a highly specific systemic lupus erythematosus (SLE) autoantibody. This study aimed to determine the prevalence of the type I IFN signature in the peripheral blood mononuclear cells of PAPS patients without specific SLE autoantibodies and search for its clinical associations.

METHODS: Fifty-three PAPS patients (Sydney's criteria) were consecutively selected and age-matched with 50 healthy controls. A third group of nonimmune-mediated thrombophilia patients was also included. The expression of 41 IFN-induced genes was analyzed using real time quantitative PCR. A principal component analysis determined which genes composed the IFN signature, and the z-score was calculated. An ROC curve defined the signature cut-off.

RESULTS: Six genes remained in the IFN signature DNAJA1, IFIT5, IFI27, MX1, IFI6, and TYK2. The ROC cutoff was 3.9-fold (AUC = 0.706, S = 0.49, E = 0.86, PPV = 0.79, NPV = 0.61). The type I IFN signature was present in 49% of the patients with PAPS compared with 14.0% of the healthy controls and 17% of the nonimmune-mediated thrombophilia patients (p < .0001). The IFN signature was associated with a younger age at the first antiphospholipid syndrome event (p = .023) and with preeclampsia (p = .032).

CONCLUSION: Our results indicate that PAPS patients without lupus-specific antibodies have an enhanced type I IFN gene signature that is not observed in nonimmune-mediated thrombophilia. Also, this overexpression of type I IFN-regulated genes associated with an earlier onset of antiphospholipid syndrome event and preeclampsia.