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Background Protein kinase C (PKC) θ, a serine/threonine kinase, is involved in T H 2 cell activation and proliferation. Type 2 innate lymphoid cells (ILC2s) resemble T H 2 cells and produce the T H 2 cytokines IL-5 and IL-13 but lack antigen-specific receptors. The mechanism by which PKC-θ drives innate immune cells to instruct T H 2 responses in patients with allergic lung inflammation remains unknown. Objectives We hypothesized that PKC-θ contributes to ILC2 activation and might be necessary for ILC2s to instruct the T H 2 response. Methods PRKCQ gene expression was assessed in innate lymphoid cell subsets purified from human PBMCs and mouse lung ILC2s. ILC2 activation and eosinophil recruitment, T H 2-related cytokine and chemokine production, lung histopathology, interferon regulatory factor 4 (IRF4) mRNA expression, and nuclear factor of activated T cells (NFAT1) protein expression were determined. Adoptive transfer of ILC2s from wild-type mice was performed in wild-type and PKC-θ–deficient (PKC-θ −/− ) mice. Results Here we report that PKC-θ is expressed in both human and mouse ILC2s. Mice lacking PKC-θ had reduced ILC2 numbers, T H 2 cell numbers and activation, airway hyperresponsiveness, and expression of the transcription factors IRF4 and NFAT1. Importantly, adoptive transfer of ILC2s restored eosinophil influx and IL-4, IL-5 and IL-13 production in lung tissue, as well as T H 2 cell activation. The pharmacologic PKC-θ inhibitor (Compound 20) administered during allergen challenge reduced ILC2 numbers and activation, as well as airway inflammation and IRF4 and NFAT1 expression. Conclusions Therefore our findings identify PKC-θ as a critical factor for ILC2 activation that contributes to T H 2 cell differentiation, which is associated with IRF4 and NFAT1 expression in allergic lung inflammation. [ABSTRACT FROM AUTHOR]

To ensure the B cell differentiation stage specificity of the intronic Eμ element and of the locus control region (LCR) that lies downstream of the IgH chain locus, we generated transgenic mice harboring a VH promoter-GFP reporter gene linked to the 3′LCR region and the Eμ element. By flow cytometry, GFP+ lymphocytes were observed amongst pro-B cells (B220+CD43+CD117+) and at all stages of differentiation up to mature B cells (B220+IgM+IgD+). Expression was strictly confined to cells committed to the B lymphocyte lineage as judged by the lack of GFP+Thy1,2+ cells (T lymphocytes) and GFP+B220−CD117+CD43+ cells (uncommitted lymphohematopoietic progenitors). Therefore, the Eμ-GFP-3′LCR transgene is not expressed by hematopoietic stem cells, begins its expression in pro-B cells and is specifically active at all stages of B cell maturation. The combination of 3′ and 5′ IgH regulatory elements thus appears as a potentially useful cassette in transgenes that require a stringent and early B lineage-specific expression. [Copyright &y& Elsevier]

Transgenic mice were generated to identify the first B cell maturation stage showing expression of an immunoglobulin transcriptional enhancer element (Eμ)-green fluorescent protein (GFP) transgene, and to check the ability of the Eμ element to behave as a locus control region. Flow cytometry experiments indicated that stably transfected 18–81 cells (a murine pre-B cell line) and A20 cells (a murine IgM+ B cell line) maintained a constant GFP expression for several months in culture. Contrasting with in vitro results, flow cytometry experiments did not highlight GFP+ B cells in spleen and bone marrow of Eμ-GFP transgenic mice and no GFP transcripts were detected by Northern blot and reverse transcriptase polymerase chain reaction analysis. In transgenic mice, the lack of GFP expression seemed related to transgene DNA methylation occurring within all organs. Our results show dramatic differences for expression of the Eμ-GFP transgene in vitro and in vivo. Despite that Eμ was reported to efficiently control the in vivo expression of other associated transgenes, it is not sufficient to sustain GFP expression in transgenic mice and to counteract developmental silencing programs that occur in the embryo. [Copyright &y& Elsevier]

Summary Recent observations clearly highlight the critical role of type 2 innate lymphoid cells in maintaining the homeostasis of adipose tissues in humans and mice. This cell population promotes beiging and limits adiposity directly and indirectly by sustaining a Th2-prone environment enriched in eosinophils and alternatively activated macrophages. Accordingly, the number and function of type 2 innate lymphoid cells (ILC2s) are strongly impaired in obese individuals. In this work, we identify the PD-1-PD-L1 pathway as a factor leading to ILC2 destabilization upon high-fat feeding resulting in impaired tissue metabolism. Tumor necrosis factor (TNF) appears to play a central role, triggering interleukin-33 (IL-33)-dependent PD-1 expression on ILC2s and recruiting and activating PD-L1hi M1 macrophages. PD-1 blockade partially restores the type 2 innate axis, raising the possibility of restoring tissue homeostasis. Graphical Abstract Highlights • PD-1 is upregulated on ILC2s in adipose tissue of obese mice • PD-1 expression is increased in a TNF- and IL-33-dependent manner • PD-1 correlates with impaired ILC2 function in the presence of PD-L1+ macrophages • PD-1 blockade ameliorates glucose tolerance and adaptation to environmental cold The function of ILC2s is compromised during obesity. Here, Oldenhove et al. show that ILC2 inhibition is mediated by the PD-1-PD-L1 pathway. PD-1 blockade in obese mice improved ILC2 function, reinforced type 2 innate responses, and promoted tissue homeostasis. PD-1 may therefore represent a target for immune intervention in obesity-associated disorders. [ABSTRACT FROM AUTHOR]

Abstract: Tumor necrosis factor (TNF) is critical and non-redundant to control Mycobacterium tuberculosis infection and cannot be replaced by other proinflammatory cytokines. Overproduction of TNF may cause immunopathology, while TNF neutralization reactivates latent and chronic, controlled infection, which is relevant for the use of neutralizing TNF therapies in patients with rheumatoid arthritis. [Copyright &y& Elsevier]

The control of Mycobacterium tuberculosis infection depends on recognition of the pathogen and the activation of both the innate and adaptive immune responses. Toll-like receptors (TLR) were shown to play a critical role in the recognition of several pathogens. Mycobacterial antigens recognise distinct TLR resulting in rapid activation of cells of the innate immune system. Recent evidence from in vitro and in vivo investigations, summarised in this review demonstrates TLR-dependent activation of innate immune response, while the induction of adaptive immunity to mycobacteria may be TLR independent. [Copyright &y& Elsevier]