Complexed soluble IL-7 receptor α and IL-7 increase IL-7-mediated proliferation and viability of CD8⁺ T-cells in vitro.

Many soluble cytokine receptors inhibit cytokine bioactivity, while others prolong ligand activity. The biological role of an endogenous soluble form of IL-7Rα, or its therapeutic effects on CD8(+) T-cells are unknown. We demonstrate that recombinant IL-7Rα-Fc, when pre-incubated with IL-7, enhances IL-7-induced CD8(+) T-cell proliferation and viability of human or murine CD8(+) T-cells. Receptor blocking experiments confirmed IL-7-specific activity. These data demonstrate that exogenous soluble IL-7Rα significantly enhances CD8(+) T-cell responses to IL-7 in vitro and paves the way for future research to determine its therapeutic potential to restore impaired CD8(+) T-cell function in disease.

The hypermorphic PLCγ2 S707Y variant dysregulates microglial cell function - Insight into PLCγ2 activation in brain health and disease, and opportunities for therapeutic modulation.

Phospholipase C-gamma 2 (PLCγ2) is highly expressed in hematopoietic and immune cells, where it is a key signalling node enabling diverse cellular functions. Within the periphery, gain-of-function (GOF) PLCγ2 variants, such as the strongly hypermorphic S707Y, cause severe immune dysregulation. The milder hypermorphic mutation PLCγ2 P522R increases longevity and confers protection in central nervous system (CNS) neurodegenerative disorders, implicating PLCγ2 as a novel therapeutic target for treating these CNS indications. Currently, nothing is known about what consequences strong PLCγ2 GOF has on CNS functionality, and more precisely on the specific biological functions of microglia. Using the PLCγ2 S707Y variant as a model of chronic activation we investigated the functional consequences of strong PLCγ2 GOF on human microglia. PLCγ2 S707Y expressing human inducible pluripotent stem cells (hiPSC)-derived microglia exhibited hypermorphic enzymatic activity under both basal and stimulated conditions, compared to PLCγ2 wild type. Despite the increase in PLCγ2 enzymatic activity, the PLCγ2 S707Y hiPSC-derived microglia display diminished functionality for key microglial processes including phagocytosis and cytokine secretion upon inflammatory challenge. RNA sequencing revealed a downregulation of genes related to innate immunity and response, providing molecular support for the phenotype observed. Our data suggests that chronic activation of PLCγ2 elicits a detrimental phenotype that is contributing to unfavourable CNS functions, and informs on the therapeutic window for targeting PLCγ2 in the CNS. Drug candidates targeting PLCγ2 will need to precisely mimic the effects of the PLCγ2 P522R variant on microglial function, but not those of the PLCγ2 S707Y variant.

Immune disease risk variants regulate gene expression dynamics during CD4+ T cell activation.

During activation, T cells undergo extensive gene expression changes that shape the properties of cells to exert their effector function. Understanding the regulation of this process could help explain how genetic variants predispose to immune diseases. Here, we mapped genetic effects on gene expression (expression quantitative trait loci (eQTLs)) using single-cell transcriptomics. We profiled 655,349 CD4+ T cells, capturing transcriptional states of unstimulated cells and three time points of cell activation in 119 healthy individuals. This identified 38 cell clusters, including transient clusters that were only present at individual time points of activation. We found 6,407 genes whose expression was correlated with genetic variation, of which 2,265 (35%) were dynamically regulated during activation. Furthermore, 127 genes were regulated by variants associated with immune-mediated diseases, with significant enrichment for dynamic effects. Our results emphasize the importance of studying context-specific gene expression regulation and provide insights into the mechanisms underlying genetic susceptibility to immune-mediated diseases.

Generation of a Crigler-Najjar Syndrome Type I patient-derived induced pluripotent stem cell line CNS705 (HHUUKDi005-A).

Human fibroblasts cells from a Crigler-Najjar Syndrome (CNS) patient were used to generate integration-free induced pluripotent stem cells (iPSCs) by over-expressing episomal-based plasmids expressing OCT4, SOX2, NANOG, KLF4, c-MYC and LIN28. The derived CNS705-iPSC line is homozygous for the UGT1A1 c.877_890delTACATTAATGCTTCinsA mutation. Pluripotency was confirmed by the expression of associated markers and embryoid body-based differentiation into cell types from all three germ layers. Comparative transcriptome analysis of the iPSC and the human embryonic stem cell line H9 revealed a Pearson's correlation of 0.9468.

Somatic mosaicism and common genetic variation contribute to the risk of very-early-onset inflammatory bowel disease.

Very-early-onset inflammatory bowel disease (VEO-IBD) is a heterogeneous phenotype associated with a spectrum of rare Mendelian disorders. Here, we perform whole-exome-sequencing and genome-wide genotyping in 145 patients (median age-at-diagnosis of 3.5 years), in whom no Mendelian disorders were clinically suspected. In five patients we detect a primary immunodeficiency or enteropathy, with clinical consequences (XIAP, CYBA, SH2D1A, PCSK1). We also present a case study of a VEO-IBD patient with a mosaic de novo, pathogenic allele in CYBB. The mutation is present in ~70% of phagocytes and sufficient to result in defective bacterial handling but not life-threatening infections. Finally, we show that VEO-IBD patients have, on average, higher IBD polygenic risk scores than population controls (99 patients and 18,780 controls; P < 4 × 10-10), and replicate this finding in an independent cohort of VEO-IBD cases and controls (117 patients and 2,603 controls; P < 5 × 10-10). This discovery indicates that a polygenic component operates in VEO-IBD pathogenesis.