IL-1β has emerged as a key mediator of the cytokine storm linked to high morbidity and mortality from COVID-19 and blockade of the IL-1 receptor (IL-1R) with Anakinra has entered clinical trials in COVID-19 subjects. Yet, knowledge of the specific immune cell subsets targeted by IL-1β and IL-1β-induced signaling pathways in humans is limited. Utilizing mass cytometry (CyTOF) of human peripheral blood mononuclear cells, we identified effector memory CD4 T cells and CD4-CD8low/-CD161+ T cells as

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... he circulating immune subtypes with the greatest expression of p-NF-κB in response to IL-1β stimulation. Notably, CCR6 distinctly identified T cells most responsive to IL-1β. Other subsets including CD11c myeloid dendritic cells (mDCs), classical monocytes (CM), two subsets of natural killer cells (CD16-CD56brightCD161- and CD16-CD56dimCD161+) and a population of lineage- (Lin-) cells expressing CD161 and CD25 also showed IL-1β-induced expression of p-NF-κB. The IL-1R antagonist, Anakinra significantly inhibited IL-1β-induced p-NF-κB in the CCR6+ T cells and CD11c mDCs with a trending inhibition in CD14 monocytes and Lin-CD161+CD25+ cells. IL-1β also induced a rapid but much less robust increase in p-p38 expression as compared to p-NF-κB in the majority of these same immune cell subsets. Prolonged IL-1β stimulation greatly increased p-STAT3 and to a much lesser extent p-STAT1 and p-STAT5 in T cell subsets, monocytes, DCs and the Lin-CD161+CD25+ cells suggesting IL-1β-induced production of downstream STAT-activating cytokines, consistent with its role in cytokine storm. Interindividual heterogeneity and inhibition of this activation by Anakinra raises the intriguing possibility that assays to measure IL-1β-induced p-NF-κB in CCR6+ T cell subtypes could identify those at higher risk of cytokine storm and those most likely to benefit from Anakinra therapy.