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The activated immune system monopolizes the pool of amino acids in blood, diverting them from the brain and thus restricting the synthesis of serotonin and dopamine. Fagarasan and colleagues (p 1342; News and Views by Boussiotis p 1281) show that chronic activation of T cells leads to behavioral abnormalities in mice deficient in the inhibitory receptor PD-1. The original image by Matteo Guerrini shows tryptophan hydroxylase–positive neurons (yellow) devoid of serotonin (magenta) in the raphe nuclei (cyan) of PD-1-deficient mice. Art work by Erin Dewalt.
High-throughput sequencing of B and T cell receptors is routinely being applied in studies of adaptive immunity. The Adaptive Immune Receptor Repertoire (AIRR) Community was formed in 2015 to address issues in AIRR sequencing studies, including the development of reporting standards for the sharing of data sets.
Abolishing signals mediated by the inhibitory receptor PD-1 results in a systemic decrease in tryptophan and tyrosine, which leads to a striking deficiency in the neurotransmitters serotonin and dopamine in the brain and anxiety-like behavior and exacerbated fear.
Mucosal-associated invariant T cells (MAIT cells) normally preserve gut-barrier integrity but can switch their phenotype to have a pathogenic role in type 1 diabetes.
Adenosine produced by apoptotic regulatory T cells (Treg cells) has a more important immunosuppressive role in the tumor microenvironment than that of live Treg cells. This discovery raises the possibility of novel strategies for cancer immunotherapy.
NLR proteins contribute to antiviral immune responses. Lemon and colleagues show that NLRX1 promotes antiviral responses in hepatocytes by competing with the kinase PKR for viral double-stranded RNA, which allows accumulation of the transcription factor IRF1 for early control of viral replication.
Gillet and colleagues find that infection with a gammaherpesvirus confers strong and lasting protection against airway allergy through the replacement of lung-resident alveolar macrophages with recruited regulatory monocytes of bone marrow origin.
Type 1 diabetes has a multifactorial etiology. Lehuen and colleagues demonstrate that MAIT cells serve both positive roles and negative roles in type 1 diabetes by maintaining gut integrity and limiting pancreatic inflammation but also directly destroying β-cells.
The tumor microenvironment represents a stressful cellular environment. Zou and colleagues show that Treg cells in tumors have heightened sensitivity to apoptosis, but unexpectedly this increases their suppressive potency.
Fagarasan and colleagues show that excessive activation of T cells in mice deficient in the inhibitory receptor PD-1 causes a systemic decrease in tryptophan and tyrosine, which leads to deficiency in serotonin and dopamine in the brain and behavioral changes.
The polarization of leukocytes toward chemoattractants is essential for their directed migration. Chen and colleagues show that the phosphoinositide-transfer protein TIPE2 functions as a coordinator of leukocyte polarity.