Summary The signals guiding differentiation of innate lymphoid cells (ILCs) within tissues are not well understood. Salivary gland (SG) ILCs as well as liver and intestinal intraepithelial ILC1 have markers that denote tissue residency and transforming growth factor–β (TGF-β) imprinting. We deleted Tgfbr2 in cells expressing the ILC and NK marker NKp46 and found that SG ILCs were reduced in number. They lost distinct tissue markers, such as CD49a, and the effector molecules TRAIL and CD73. Expression of the transcription factor Eomes, which promotes NK cell differentiation, was elevated. Conversely, Eomes deletion in NKp46+ cells enhanced TGF-β-imprinting of SG ILCs. Thus, TGF-β induces SG ILC differentiation by suppressing Eomes. TGF-β acted through a JNK-dependent, Smad4-independent pathway. Transcriptome analysis demonstrated that SG ILCs had characteristic of both NK cells and ILC1. Finally, TGF-β imprinting of SG ILCs was synchronized with SG development, highlighting the impact of tissue microenvironment on ILC development

Summary MicroRNAs (miRNAs) can influence lineage choice or affect critical developmental checkpoints during hematopoiesis. To search for a role of the recently described p53-induced microRNA, miR-34a, in hematopoiesis, we performed gain-of-function analysis in murine bone marrow. Constitutive expression of miR-34a led to a block in B cell development at the pro-B cell to pre-B cell transition, leading to a reduction in mature B cells. This block appeared to be mediated primarily by inhibited expression of the Forkhead transcription factor, Foxp1. We demonstrated that Foxp1 was a direct target of miR-34a in a 3′-untranslated region (UTR)-dependent fashion. Knockdown of Foxp1 by siRNA recapitulated the B cell developmental phenotype induced by miR-34a, whereas co-transduction of Foxp1 lacking its 3′UTR with miR-34a rescued B cell maturation. Lastly, knockdown of miR-34a resulted in increased amounts of Foxp1 and mature B cells. These findings identify a role for miR-34a in connecting the p53 network with suppression of Foxp1, a known B cell oncogene.

Nfil3 is critical for normal development of innate lymphoid cell (ILC) progenitors. Nfil3-deficient mice have severely reduced lung and visceral adipose tissue ILC2s and gut-associated ILC3s, and compromised innate immunity to acute bacterial infection.

Anti–4-1BB treatment of tumor-bearing or intracellular pathogen infected mice generates a population of Eomes+KLRG1+ tumor infiltrating T cells that have enhanced cytotoxic activity.

Natural killer (NK) cells are innate lymphocytes that are critical for host protection against pathogens and cancer due to their ability to rapidly release inflammatory cytokines and kill infected or transformed cells. In the 40 years since their initial discovery, much has been learned about how this important cellular lineage develops and functions. We now know that NK cells are the founding members of an expanded family of lymphocyte known as innate lymphoid cells (ILC). Furthermore, we have recently discovered that NK cells can possess features of adaptive immunity such as antigen specificity and long-lived memory responses. Here we will review our current understanding of the molecular mechanisms driving development of NK cells from the common lymphoid progenitor (CLP) to mature NK cells, and from activated effectors to long-lived memory NK cells.

Autophagy is an essential cellular survival mechanism that is required for adaptive lymphocyte development; however, its role in innate lymphoid cell (ILC) development remains unknown. Furthermore, the conditions that promote lymphocyte autophagy during homeostasis are poorly understood. Here we demonstrate that Atg5, an essential component of the autophagy machinery, is required for the development of mature natural killer (NK) cells and group 1, 2, and 3 innate lymphoid cells (ILC). While inducible ablation of Atg5 was dispensable for the homeostasis of lymphocyte precursors and mature lymphocytes in lymphoreplete mice, we found that autophagy is induced in both adaptive and innate lymphocytes during homeostatic proliferation in lymphopenic hosts to promote their survival by limiting cell-intrinsic apoptosis. Induction of autophagy through metformin treatment following homeostatic proliferation increased lymphocyte numbers through an Atg5-dependent mechanism. These findings highlight the essential role for autophagy in ILC development and lymphocyte survival during lymphopenia.

No abstract

Following treatment with 4-1BB agonist antibody, a novel population of KLRG1+ T-cells infiltrate murine melanoma. Compared to their KLRG1- counterparts, these T-cells express high levels of cytotoxicity associated genes in both the CD4 and CD8 lineages, and exhibit enhanced tumor-specific killing in vitro. The phenotype of these KLRG1+ cells is dependent on high expression of the T-box transcription factor Eomesodermin (Eomes). Interestingly, only activation of 4-1BB, not other TNFR family members generates this phenotype. The root of this difference appears to be that 4-1BB is expressed by antigen presenting cells (APC) which respond to its activation by producing cytokines which promote the development of these Eomes+KLRG1+ T-cells. By analyzing changes in APC cytokine production in vivo, and by using a series of gene knockout mice we have identified the factors necessary to generate this novel T-cell lineage. These T-cells represent a novel polarity we have termed ThEO (CD4) and TcEO (CD8) which resolve multiple questions associated with 4-1BB activation including how 4-1BB enhances tumor-specific cytotoxicity and how 4-1BB can promote tumor immunity while repressing autoimmunity. Understanding the nature of this novel lineage of highly tumoricidal T-cells in both tumor and pathogen-specific immunity may provide critical information for converting sub-optimal anti-tumor responses to therapeutically successful ones.