Natural killer cells and type II interferon in Ro/SSA and La/SSB autoantibody-exposed newborns at risk of congenital heart block.

OBJECTIVE: Congenital heart block (CHB) with immune cell infiltration develops in the fetus after exposure to maternal Ro/La autoantibodies. CHB-related serology has been extensively studied, but reports on immune-cell profiles of anti-Ro/La-exposed neonates are lacking. In the current study, we characterised circulating immune-cell populations in anti-Ro/La+mothers and newborns, and explored potential downstream effects of skewed neonatal cell populations. METHODS: In total, blood from mothers (n=43) and neonates (n=66) was sampled at birth from anti-Ro/La+ (n=36) and control (n=30) pregnancies with or without rheumatic disease and CHB. Flow cytometry, microarrays and ELISA were used for characterising cells and plasma. RESULTS: Similar to non-pregnant systemic lupus erythematosus and Sjögren-patients, anti-Ro/La+mothers had altered B-cell subset frequencies, relative T-cell lymphopenia and lower natural killer (NK)-cell frequencies. Surprisingly, their anti-Ro/La exposed neonates presented higher frequencies of CD56dimCD16hi NK cells (p<0.01), but no other cell frequency differences compared with controls. Type I and II interferon (IFN) gene-signatures were revealed in neonates of anti-Ro/La+ pregnancy, and exposure of fetal cardiomyocytes to type I IFN induced upregulation of several NK-cell chemoattractants and activating ligands. Intracellular flow cytometry revealed IFNγ production by NK cells, CD8+ and CD4+ T cells in anti-Ro/La exposed neonates. IFNγ was also detectable in their plasma. CONCLUSION: Our study demonstrates an increased frequency of NK cells in anti-Ro/La exposed neonates, footprints of type I and II IFN and an upregulation of ligands activating NK cells in fetal cardiac cells after type I IFN exposure. These novel observations demonstrate innate immune activation in neonates of anti-Ro/La+pregnancy, which could contribute to the risk of CHB.

Type I IFN system activation in newborns exposed to Ro/SSA and La/SSB autoantibodies in utero.

OBJECTIVE: In utero exposure of the fetus to Ro/La autoantibodies may lead to congenital heart block (CHB). In the mother, these autoantibodies are associated with activation of the type I interferon (IFN)-system. As maternal autoantibodies are transferred to the fetus during pregnancy, we investigated whether the type I IFN-system is activated also in newborns of anti-Ro/La positive mothers, and whether fetal IFN activation is affected by maternal immunomodulatory treatment. METHODS: Blood drawn at birth from anti-Ro/La positive mothers, their newborns and healthy control pairs was separated into plasma and peripheral blood mononuclear cells (PBMC). PBMC were analysed directly or cultured. mRNA expression was analysed by microarrays, cell surface markers by flow cytometry, and IFNα levels by immunoassays. RESULTS: We observed increased expression of IFN-regulated genes and elevated plasma IFNα levels not only in anti-Ro/La positive women, but also in their newborns. CD14+ monocytes of both anti-Ro/La positive mothers and their neonates showed increased expression of Sialic acid-binding Ig-like lectin-1, indicating cellular activation. Notably, the IFN score of neonates born to mothers receiving immunomodulatory treatment was similar to that of controls, despite persistent IFN activation in the mothers. In both maternal and neonatal PBMC, IFNα production was induced when cells were cultured with anti-Ro/La positive plasma. CONCLUSIONS: Ro/La autoantibody-exposed neonates at risk of CHB have signs of an activated immune system with an IFN signature. This study further demonstrates that neonatal cells can produce IFNα when exposed to autoantibody-containing plasma, and that maternal immunomodulatory treatment may diminish the expression of IFN-regulated genes in the fetus.

Viral antigens elicit augmented immune responses in primary Sjögren's syndrome.

OBJECTIVES: Infections have been suggested in the pathogenesis of primary SS (pSS). Systematic studies of immune responses to microbial antigens in vivo may be performed during vaccination. In the present study, we therefore longitudinally followed patients with pSS and controls during split-virion influenza vaccination to identify pSS-specific cellular, transcriptomic and serological responses. METHODS: Patients without treatment (pSSUntr, n = 17), on hydroxychloroquine-treatment (pSSHCQ, n = 8), and healthy controls (n = 16) were included. Antibody titres were determined by ELISA. Plasma proteins were measured by proximity extension assay. Monocyte gene expression was assessed by Nanostring. Routine laboratory tests were performed and clinical disease symptoms were registered by questionnaires. RESULTS: pSSUntr developed higher vaccine-specific IgG titres compared with controls. Notably, anti-Ro52 autoantibody titres increased in pSSUntr but remained unchanged in pSSHCQ. No changes in disease symptoms including EULAR Sjögren's Syndrome Patient Reported Index score were registered. Twenty-four hours after vaccination, the leucocyte count in pSSUntr decreased, with a concomitant increase of CCL7 in plasma. Transcriptomic analysis in monocytes revealed differential vaccination-related expression of the NEMO/IKBKG gene, and its higher induced expression in pSSUntr associated with higher serological vaccine responses. Moreover, titres of vaccine-specific antibodies were associated with higher vaccination-induced NF-κB signalling and higher steady-state IFN signatures in monocytes, and with the levels of several plasma proteins with soluble PD-1 displaying the strongest association. CONCLUSION: We observed augmented innate and adaptive immune responses in pSS following viral antigen exposure suggesting an underlying hyper-responsiveness to immune challenges, supporting a role for infections driving the immunopathology and acting as environmental risk factor for pSS.