SummaryMigration of activated regulatory T (Treg) cells to inflamed tissue is crucial for their immune-modulatory function. While metabolic reprogramming during Treg cell differentiation has been extensively studied, the bioenergetics of Treg cell trafficking remains undefined. We have investigated the metabolic demands of migrating Treg cells in vitro and in vivo. We show that glycolysis was instrumental for their migration and was initiated by pro-migratory stimuli via a PI3K-mTORC2-mediated pathway culminating in induction of the enzyme glucokinase (GCK). Subsequently, GCK promoted cytoskeletal rearrangements by associating with actin. Treg cells lacking this pathway were functionally suppressive but failed to migrate to skin allografts and inhibit rejection. Similarly, human carriers of a loss-of-function GCK regulatory protein gene—leading to increased GCK activity—had reduced numbers of circulating Treg cells. These cells displayed enhanced migratory activity but similar suppressive function, while conventional T cells were unaffected. Thus, GCK-dependent glycolysis regulates Treg cell migration.

Although neutrophils are known to be fundamental in controlling innate immune responses, their role in regulating adaptive immunity is just starting to be appreciated. We report that human neutrophils exposed to pregnancy hormones progesterone and estriol promote the establishment of maternal tolerance through the induction of a population of CD4+ T cells displaying a GARP+CD127loFOXP3+ phenotype following antigen activation. Neutrophil-induced T (niT) cells produce IL-10, IL-17, and VEGF and promote vessel growth in vitro. Neutrophil depletion during murine pregnancy leads to abnormal development of the fetal-maternal unit and reduced empbryo development, with placental architecture displaying poor trophoblast invasion and spiral artery development in the maternal decidua, accompanied by significantly attenuated niT cell numbers in draining lymph nodes. Using CD45 congenic cells, we show that induction of niT cells and their regulatory function occurs via transfer of apoptotic neutrophil-derived proteins, including forkhead box protein 1 (FOXO1), to T cells. Unlike in women with healthy pregnancies, neutrophils from blood and placental samples of preeclamptic women fail to induce niT cells as a direct consequence of their inability to transfer FOXO1 to T cells. Finally, neutrophil-selective FOXO1 knockdown leads to defective placentation and compromised embryo development, similar to that resulting from neutrophil depletion. These data define a nonredundant function of neutrophil–T cell interactions in the regulation of vascularization at the maternal–fetal interface.

SummaryEffector-T-cell-mediated immunity depends on the efficient localization of antigen-primed lymphocytes to antigen-rich non-lymphoid tissue, which is facilitated by the expression of a unique set of “homing” receptors acquired by memory T cells. We report that engagement of the hepatocyte growth factor (HGF) receptor c-Met by heart-produced HGF during priming in the lymph nodes instructs T cell cardiotropism, which was associated with a specialized homing “signature” (c-Met+CCR4+CXCR3+). c-Met signals facilitated T cell recruitment to the heart via the chemokine receptor CCR5 by inducing autocrine CCR5 ligand release. c-Met triggering was sufficient to support cardiotropic T cell recirculation, while CCR4 and CXCR3 sustained recruitment during heart inflammation. Transient pharmacological blockade of c-Met during T cell priming led to enhanced survival of heart, but not skin, allografts associated with impaired localization of alloreactive T cells to heart grafts. These findings suggest c-Met as a target for development of organ-selective immunosuppressive therapies.