Project description:Calcium signals are initiated in immune cells by the process of store-operated calcium entry (SOCE), where receptor activation triggers transient calcium release from the endoplasmic reticulum, followed by opening of plasma membrane calcium-release activated calcium (CRAC) channels. ORAI1, ORAI2 and ORAI3 are known to comprise the CRAC channel, however the contributions of individual isoforms to neutrophil function is not well understood. Here we show that loss of ORAI1 partially decreases calcium influx while loss of both ORAI1 and ORAI2 completely abolishes store-operated calcium entry. In other immune cell types, loss of ORAI2 enhances SOCE. In contrast, we find that ORAI2-deficient neutrophils display decreased calcium influx, which is correlated with measurable differences in regulation of neutrophil membrane potential via KCa3.1. Decreased SOCE in ORAI1-, ORAI2- and ORAI1/2-deficient neutrophils impairs multiple neutrophil functions including phagocytosis, degranulation, leukotriene and ROS production, rendering ORAI1/2-deficient mice highly susceptible to staphylococcal infection. This study demonstrates that ORAI1 and ORAI2 are the primary components of the neutrophil CRAC channel and identifies novel subpopulations of neutrophils where cell membrane potential functions as a rheostat to modulate the SOCE response. These findings have implications for new mechanisms that modulate neutrophil function during infection, acute and chronic inflammatory conditions, and cancer.
Project description:Neutrophils provide immune protection against pathogens but also may promote tissue injury in inflammatory diseases. Although neutrophils are generally considered as a relatively homogeneous population, evidence for heterogeneity is emerging. Under steady-state conditions, neutrophil heterogeneity may arise from ageing and the replenishment by newly released neutrophils from the bone marrow. We used microarray to globally analyze gene expression in aged neutrophils and characterize the inflammatory programs that are activated during the aging process in the circulation. Control, aged and activated neutrophils were sorted directly from mouse blood for RNA extraction and hybridization on Affymetrix microarrays. We transfused whole blood and harvested donor neutrophils marked by the CD45.1 allele 6h later to derive neutrophils that had truly aged in vivo. Sorted neutrophils were compared to control donor neutrophils that had been transferred for only 10 min. Additionally, we harvested circulating neutrophils from TNF-? treated mice for comparison with neutrophils activated by systemic inflammation.
Project description:Myeloid-derived suppressor cells (MDSCs) have the capacity to suppress T cell-mediated immune responses, and impact clinical outcome of cancer, infections and transplantation settings. Although MDSCs were initially described as bone-marrow-derived immature myeloid cells (either monocytic [m-MDSC] or granulocytic [g-MDSC]), also mature neutrophils have been shown to exert MDSC activity towards T cells, in ways that so far remained unclear. In this study, we demonstrate that human neutrophils – both from healthy donors and cancer patients – do not exert MDSC activity unless they are activated. Using neutrophils with genetically well-defined defects, we found that reactive oxygen species (ROS) and granule-derived constituents are required for MDSC activity after direct CD11b-dependent neutrophil-T cell interactions. Besides these cellular interactions, neutrophils were engaged in the uptake of pieces of T cell membrane, a process called trogocytosis. Together, these interactions led to changes in T cell morphology, mitochondrial dysfunction and ATP depletion, as indicated by electron microscopy, mass spectrometry and metabolic parameters. Our studies characterize the different steps by which activated mature neutrophils induce functional T cell non-responsiveness and irreparable cell damage.
Project description:Neutrophils provide immune protection against pathogens but also may promote tissue injury in inflammatory diseases. Although neutrophils are generally considered as a relatively homogeneous population, evidence for heterogeneity is emerging. Under steady-state conditions, neutrophil heterogeneity may arise from ageing and the replenishment by newly released neutrophils from the bone marrow. We used microarray to globally analyze gene expression in aged neutrophils and characterize the inflammatory programs that are activated during the aging process in the circulation.