P2Y6 Signaling Controls an Innate Alveolar Macrophage-NK Cell Axis That Dampens Type 2 Lung Immunopathology

Abstract

Type 6 purinergic (P2Y6) receptors are high affinity G protein-coupled receptors (GPCRs) for uridine diphosphate (UDP). We found that P2Y6 receptor expression during the sensitization phase plays a critical role in preventing sensitization to the allergen. In this study, we sought to identify key steps and cell types response for the protective effect of P2Y6 receptors. p2ry6(flox/flox);rosa26creER/+ and p2ry6(flox/flox);+/+ controls were treated with tamoxifen starting either 10 days before the initial sensitization. The mice were sensitized with an extract from Dermatophagoides farinae (Df) intranasally on days 0 and 1. We examined BAL fluid from P2ry6flox/flox/Cre/+ mice and +/+ controls for Th1 cytokines by alveolar macrophages, as well as the NK cell activation, during the sensitization phase. BAL fluid levels of IL-12p40, expression of IFNγ, and M1-cytokine/chemokine transcripts by BAL fluid cells increased sharply in response to 2 sensitizing doses of Df in +/+ but not in P2ry6flox/flox/Cre/+ mice. Alveolar macrophages were the dominant source of P2Y6 receptor-dependent IL-12p40 expression, driving IFNγ production by NK cells. The IL-12-restored P2ry6flox/flox/Cre/+ mice showed significantly increased expression of IFNγ at day2 and decreased BAL fluid eosinophils at day 16, compared to the Df-treated +/+ controls. Antibody depletion of NK cells before sensitization abolished the protective effect of P2Y6 receptors. Alveolar macrophages use UDP-P2Y6 signalling to drive an innate IL-12/NK cell axis that strongly influences the outcome of respiratory allergen exposure.