Innate immunodeficiency following genetic ablation of Mcl1 in natural killer cells

The cytokine IL-15 is required for natural killer (NK) cell homeostasis; however, the intrinsic mechanism governing this requirement remains unexplored. Here we identify the absolute requirement for myeloid cell leukaemia sequence-1 (Mcl1) in the sustained survival of NK cells in vivo. Mcl1 is highly expressed in NK cells and regulated by IL-15 in a dose-dependent manner via STAT5 phosphorylation and subsequent binding to the 3'-UTR of Mcl1. Specific deletion of Mcl1 in NK cells results in the absolute loss of NK cells from all tissues owing to a failure to antagonize pro-apoptotic proteins in the outer mitochondrial membrane. This NK lymphopenia results in mice succumbing to multiorgan melanoma metastases, being permissive to allogeneic transplantation and being resistant to toxic shock following polymicrobial sepsis challenge. These results clearly demonstrate a non-redundant pathway linking IL-15 to Mcl1 in the maintenance of NK cells and innate immune responses in vivo

Genomic epidemiology of SARS-CoV-2 in a UK university identifies dynamics of transmission

AbstractUnderstanding SARS-CoV-2 transmission in higher education settings is important to limit spread between students, and into at-risk populations. In this study, we sequenced 482 SARS-CoV-2 isolates from the University of Cambridge from 5 October to 6 December 2020. We perform a detailed phylogenetic comparison with 972 isolates from the surrounding community, complemented with epidemiological and contact tracing data, to determine transmission dynamics. We observe limited viral introductions into the university; the majority of student cases were linked to a single genetic cluster, likely following social gatherings at a venue outside the university. We identify considerable onward transmission associated with student accommodation and courses; this was effectively contained using local infection control measures and following a national lockdown. Transmission clusters were largely segregated within the university or the community. Our study highlights key determinants of SARS-CoV-2 transmission and effective interventions in a higher education setting that will inform public health policy during pandemics.</jats:p

Innate lymphoid cells type 3

Retinoic acid receptor-related (RAR) orphan receptor γ (Rorγt) innate lymphoid cells or group 3 innate lymphoid cells (ILC3s) play key roles in the development of lymphoid tissues, maintenance of epithelial tissue homeostasis, and repair and defense against pathogens encountered at the body's barriers. These cells produce interleukin (IL)-22, IL-17A, and lymphotoxin (LT)αβ which are critical cytokines necessary for induction of the protective pathways at epithelial and mucosal surfaces. The ILC3 are a heterogeneous group of cells. Significant efforts have been made to decipher the transcriptional program that regulates their development and to understand the functions and mechanisms of actions of the individual subsets in providing immune protection

Nfil3 is required for the development of all innate lymphoid cell subsets

Innate lymphoid cell (ILC) populations protect against infection and are essential for lymphoid tissue formation and tissue remodeling after damage. Nfil3 is implicated in the function of adaptive immune lineages and NK cell development, but it is not yet known if Nfil3 regulates other innate lymphoid lineages. Here, we identify that Nfil3 is essential for the development of Peyer's patches and ILC2 and ILC3 subsets. Loss of Nfil3 selectively reduced Peyer's patch formation and was accompanied by impaired recruitment and distribution of lymphocytes within the patches. ILC subsets exhibited high Nfil3 expression and genetic deletion of Nfil3 severely compromised the development of all subsets. Subsequently, Nfil3 mice were highly susceptible to disease when challenged with inflammatory or infectious agents. Thus, we demonstrate that Nfil3 is a key regulator of the development of ILC subsets essential for immune protection in the lung and gut

Transforming growth factor-beta and Notch ligands act as opposing environmental cues in regulating the plasticity of type 3 innate lymphoid cells

International audienceGroup 3 innate lymphoid cells (ILC3s) are composed of subsets that are either positive or negative for the natural cytotoxicity receptor (NCR) NKp46 (encoded by Ncr1). ILC3s are located at mucosal sites, such as in the intestine and lung, where they are exposed to billions of commensal microbes and potentially harmful pathogens. Together with T cells, the various ILC3 subsets maintain the balance between homeostasis and immune activation. Through genetic mapping, we identified a previously uncharacterized subset of NCR- ILC3s in mice that transiently express Ncr1, demonstrating previously undescribed heterogeneity within the ILC3 population. In addition, we showed that sustained Notch signaling was required for the maintenance of the NCR+ phenotype and that the cytokine transforming growth factor-beta (TGF-beta) impaired the development of NCR+ ILC3s. Thus, the plasticity of ILC3s is regulated by the balance between the opposing effects of Notch and TGF-beta signaling, maintaining homeostasis in the face of continual challenges

The Helix-Loop-Helix Protein ID2 Governs NK Cell Fate by Tuning Their Sensitivity to Interleukin-15

International audienceThe inhibitor of DNA binding 2 (Id2) is essential for natural killer (NK) cell development with its canonical role being to antagonize E-protein function and alternate lineage fate. Here we have identified a key role for Id2 in regulating interleukin-15 (IL-15) receptor signaling and homeostasis of NK cells by repressing multiple E-protein target genes including Socs3. Id2 deletion in mature NK cells was incompatible with their homeostasis due to impaired IL-15 receptor signaling and metabolic function and this could be rescued by strong IL-15 receptor stimulation or genetic ablation of Socs3. During NK cell maturation, we observed an inverse correlation between E-protein target genes and Id2. These results shift the current paradigm on the role of ID2, indicating that it is required not only to antagonize E-proteins during NK cell commitment, but constantly required to titrate E-protein activity to regulate NK cell fitness and responsiveness to IL-15

Complementarity and redundancy of IL-22-producing innate lymphoid cells

Intestinal T cells and group 3 innate lymphoid cells (ILC3 cells) control the composition of the microbiota and gut immune responses. Within the gut, ILC3 subsets coexist that either express or lack the natural cytoxicity receptor (NCR) NKp46. We identified here the transcriptional signature associated with the transcription factor T-bet-dependent differentiation of NCR- ILC3 cells into NCR+ ILC3 cells. Contrary to the prevailing view, we found by conditional deletion of the key ILC3 genes Stat3, 1122, Tbx21 and Mcl1 that NCR+ ILC3 cells were redundant for the control of mouse colonic infection with Citrobacter rodentium in the presence of T cells. However, NCR+ ILC3 cells were essential for cecal homeostasis. Our data show that interplay between intestinal ILC3 cells and adaptive lymphocytes results in robust complementary failsafe mechanisms that ensure gut homeostasis