FRI0257 The stat4 sle risk allele rs7574865[t] is associated with increased il-12-induced ifn-gamma production in t cells from sle patients

Background Genetic variants in the transcription factor STAT4 are associated with increased susceptibility to systemic lupus erythematosus (SLE) and a more severe disease phenotype. Objectives This study aimed to clarify how the SLE-associated intronic STAT4 risk variant rs7574865[T] affects the function of immune cells in SLE. Methods Peripheral blood mononuclear cells (PBMCs) were isolated from 52 SLE patients in remission (SLEDAI-2K≤4). STAT4 and STAT1 protein levels and phosphorylation status in response to interferon (IFN)-α, IFN-γ, or interleukin (IL)−12 were determined, before and after pre-activation of cells with phytohaemagglutinin (PHA) and IL-2, in CD56 dim NK cells, CD56 bright NK cells, B cells, CD4 + T cells, CD8 + T cells and monocytes by flow cytometry. The frequency of IFN-γ + cells upon IL-12 or PMA (phorbol 12-myristate-13-acetate) stimulation and the frequency of T-bet + cells was determined in PHA/IL-2 pre-activated cells. Cellular responses and phenotypes were correlated with STAT4 risk allele carriership (rs7574865[T], 21 homozygous protective, 22 heterozygous and 9 homozygous risk) using an additive linear regression model. Janus kinase inhibitors (JAKi) selective for TYK2 (TYK2i, Compound 35) or JAK2 (JAK2i, BMS-911543) were evaluated for inhibition of IL-12 or IFN-γ-induced activation of SLE PBMCs. Results In resting PBMCs, the STAT4 risk allele was neither associated with protein levels of STAT4 or STAT1, nor cytokine-induced phosphorylation of STAT4 (pSTAT4) or STAT1 (pSTAT1). However, following PHA/IL-2-activation, CD8 + T cells from STAT4 risk allele carriers displayed increased levels of STAT4 (p=0.04), resulting in increased pSTAT4 in response to IL-12 (p=0.003) and IFN-α (p=0.04). Analysis of T cell subsets revealed that the effect was seen in CD45RA + CD57 – naive and CD45RA – CD57 – memory CD8 + T cells, but not in CD45RA – CD57 + memory or CD45RA + CD57 + effector CD8 + T cells. A slight increase in STAT4 protein levels and IL-12-induced pSTAT4 was also observed in CD4 + T cells from STAT4 risk allele carriers (p=0.08 and p=0.09, respectively). STAT4 risk allele carriers displayed an augmented IL-12-induced IFN-γ production in CD8 + and CD4 + T cells (p=0.03 for both), whereas PMA-induced IL-12 production was normal (p=0.31 and p=0.10, respectively). T-bet expression was not correlated to the STAT4 genotype. The TYK2i and the JAK2i efficiently blocked IL-12 and IFN-γ-induced activation of PBMCs from STAT4 risk patients, respectively. Conclusions T cells from SLE patients carrying the STAT4 risk allele rs7574865[T] display an augmented response to IL-12 and IFN-α. This subset of patients may benefit from JAKi treatment. Disclosure of Interest N. Hagberg: None declared, M. Joelsson: None declared, D. Leonard: None declared, S. Reid: None declared, M.-L. Eloranta: None declared, J. Mo Employee of: AstraZeneca, M. Nilsson Employee of: AstraZeneca, A.-C. Syvanen: None declared, Y. Bryceson: None declared, L. Ronnblom: None declared