Tumours progress despite being infiltrated by tumour-specific effector T cells1. Tumours contain areas of cellular necrosis, which is associated with poor survival in a variety of cancers2. Here, we show that necrosis releases an intracellular ion, potassium, into the extracellular fluid of mouse and human tumours causing profound suppression of T cell effector function. We find that elevations in the extracellular potassium concentration [K + ]e act to impair T cell receptor (TCR)-driven Akt-mTOR phosphorylation and effector programmes, this potassium-mediated suppression of Akt-mTOR signalling and T cell function is dependent upon the activity of the serine/threonine phosphatase PP2A3,4. While the suppressive effect mediated by elevated [K + ]e is independent of changes in plasma membrane potential (V m ), it does require an increase in intracellular potassium ([K + ]i). Concordantly, ionic reprogramming of tumour-specific T cells through overexpression of the potassium channel K v 1.3 lowers [K + ]i and improves effector Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use

Streptococcus pneumoniae is a major cause of pneumonia and a leading cause of death world-wide. Antibody-mediated immune responses can confer protection against repeated exposure to S. pneumoniae, yet vaccines offer only partial protection. Patients with Activated PI3Kδ Syndrome (APDS) are highly susceptible to S. pneumoniae. We generated a conditional knock-in mouse model of this disease and identify a CD19+B220− B cell subset that is induced by PI3Kδ signaling, resides in the lungs, and is correlated with increased susceptibility to S. pneumoniae during early phases of infection via an antibody-independent mechanism. We show that an inhaled PI3Kδ inhibitor improves survival rates following S. pneumoniae infection in wild-type mice and in mice with activated PI3Kδ. These results suggest that a subset of B cells in the lung can promote the severity of S. pneumoniae infection, representing a potential therapeutic target.

How the age‐associated decline of immune function leads to increased cancer incidence is poorly understood. Here, we have characterised the cellular composition of the γδ T‐cell pool in peripheral lymph nodes ( pLN s) upon ageing. We find that ageing has minimal cell‐intrinsic effects on function and global gene expression of γδ T cells, and γδ TCR diversity remains stable. However, ageing alters TCR δ chain usage and clonal structure of γδ T‐cell subsets. Importantly, IL ‐17‐producing γδ17 T cells dominate the γδ T‐cell pool of aged mice—mainly due to the selective expansion of Vγ6 + γδ17 T cells and augmented γδ17 polarisation of Vγ4 + T cells. Expansion of the γδ17 T‐cell compartment is mediated by increased IL ‐7 expression in the T‐cell zone of old mice. In a Lewis lung cancer model, pro‐tumourigenic Vγ6 + γδ17 T cells are exclusively activated in the tumour‐draining LN and their infiltration into the tumour correlates with increased tumour size in aged mice. Thus, upon ageing, substantial compositional changes in γδ T‐cell pool in the pLN lead to an unbalanced γδ T‐cell response in the tumour that is associated with accelerated tumour growth.

PI3Ks regulate diverse immune cell functions by transmitting intracellular signals from Ag, costimulatory receptors, and cytokine receptors to control cell division, differentiation, survival, and migration. In this study, we report the effect of inhibiting the p110δ subunit of PI3Kδ on CD8+ T cell responses to infection with the intracellular bacteria Listeria monocytogenes. A strong dependency on PI3Kδ for IFN-γ production by CD8+ T cells in vitro was not recapitulated after Listeria infection in vivo. Inactivation of PI3Kδ resulted in enhanced bacterial elimination by the innate immune system. However, the magnitudes of the primary and secondary CD8+ T cell responses were reduced. Moreover, PI3Kδ activity was required for CD8+ T cells to provide help to other responding CD8+ cells. These findings identify PI3Kδ as a key regulator of CD8+ T cell responses that integrates extrinsic cues, including those from other responding cells, to determine the collective behavior of CD8+ T cell populations responding to infection.