Abstract

Dendritic cells (DC) facilitate the maintenance of immunological tolerance in the steady state. We report that transcription factor Etv3 is preferentially expressed in mature DC including tissue-derived migratory DC (migDC) and facilitates their homeostatic maturation and CCR7-dependent migration. Mice with global or DC-specific deletion of Etv3 manifested the expansion of CD25low regulatory T cells (Treg), spontaneous activation of conventional T cells, and multiorgan T cell infiltration. Etv3 deficiency exacerbated TLR7-driven systemic lupus erythematosus (SLE)-like disease, supporting the reported genetic association of human ETV3 with SLE. Etv3-deficient migDC upregulated multiple costimulatory molecules including OX40 ligand (OX40L/TNFSF4), whose blockade partially rescued the Treg abnormalities. These results identified Etv3 as an essential regulator of the tolerogenic function of DC and implicate it in the regulation of human autoimmunity. 

Abstract

Type I interferons (IFN-I) including IFN-β and multiple IFN-α subtypes are key antiviral proteins encoded within a single locus. The antiviral response of most cells involves primarily IFN-β, whereas professional IFN-I-producing plasmacytoid dendritic cells (pDCs) secrete all IFN-I subtypes. We report that in pDCs prior to activation, the IFN-I locus showed distinct features including localization in the active intranuclear chromosomal compartment, establishment of distinct three-dimensional chromatin organization, and accessibility of Ifna gene promoters. Accordingly, IFN-I production specifically by pDCs required the chromatin-organizing cohesin complex. The intranuclear translocation and promoter opening were mediated by the pDC-enriched transcription factor IRF8. Finally, we identified several IRF8- and/or cohesin-binding regulatory regions across the IFN-I locus. One of these enhanced IFN-β induction in all cells, whereas two others enhanced pDC-specific induction of adjacent Ifna genes. Thus, the unique IFN-I-producing capacity of pDCs is facilitated by the anticipatory chromatin organization imparted by IRF8 and cohesin.

Abstract

Heterogeneity among naive adaptive lymphocytes determines their individual functions and fate decisions during an immune response. NK cells are innate lymphocytes capable of generating "adaptive" responses during infectious challenges. However, the factors that govern various NK cell functions are not fully understood. In this study, we use a reporter mouse model to permanently "time stamp" NK cells and type 1 innate lymphoid cells (ILC1s) to characterize the dynamics of their homeostatic turnover. We found that the homeostatic turnover of tissue-resident ILC1s is much slower than that of circulating NK cells. NK cell homeostatic turnover is further accelerated without the transcription factor Eomes. Finally, heterogeneity in NK cell age diversifies NK cell function, with "older" NK cells exhibiting more potent IFN-γ production to activating stimuli and more robust adaptive responses during CMV infection. These results provide insight into how the functional response of an NK cell varies over its lifespan.

Abstract

The process of affinity maturation, whereby T and B cells bearing antigen receptors with optimal affinity to the relevant antigen undergo preferential expansion, is a key feature of adaptive immunity. Natural killer (NK) cells are innate lymphocytes capable of “adaptive” responses after cytomegalovirus (CMV) infection. However, whether NK cells are similarly selected on the basis of their avidity for cognate ligand is unknown. Here, we showed that NK cells with the highest avidity for the mouse CMV glycoprotein m157 were preferentially selected to expand and comprise the memory NK cell pool, whereas low-avidity NK cells possessed greater capacity for interferon-γ (IFN-γ) production. Moreover, we provide evidence for avidity selection occurring in human NK cells during human CMV infection. These results delineate how heterogeneity in NK cell avidity diversifies NK cell effector function during antiviral immunity, and how avidity selection might serve to produce the most potent memory NK cells.

Abstract

Natural killer (NK) cells are innate lymphocytes that display features of adaptive immunity during viral infection. Biallelic mutations in IRF8 have been reported to cause familial NK cell deficiency and susceptibility to severe viral infection in humans; however, the precise role of this transcription factor in regulating NK cell function remains unknown. Here, we show that cell-intrinsic IRF8 was required for NK-cell-mediated protection against mouse cytomegalovirus infection. During viral exposure, NK cells upregulated IRF8 through interleukin-12 (IL-12) signaling and the transcription factor STAT4, which promoted epigenetic remodeling of the Irf8 locus. Moreover, IRF8 facilitated the proliferative burst of virus-specific NK cells by promoting expression of cell-cycle genes and directly controlling Zbtb32, a master regulator of virus-driven NK cell proliferation. These findings identify the function and cell-type-specific regulation of IRF8 in NK-cell-mediated antiviral immunity and provide a mechanistic understanding of viral susceptibility in patients with IRF8 mutations.