0000000000020356
AUTHOR
Konrad Gronke
Isolation and Flow Cytometry Analysis of Innate Lymphoid Cells from the Intestinal Lamina Propria
The intestinal mucosa constitutes the biggest surface area of the body. It is constantly challenged by bacteria, commensal and pathogenic, protozoa, and food-derived irritants. In order to maintain homeostasis, a complex network of signaling circuits has evolved that includes contributions of immune cells. In recent years a subset of lymphocytes, which belong to the innate immune system, has caught particular attention. These so-called innate lymphoid cells (ILC) reside within the lamina propria of the small and large intestines and rapidly respond to environmental challenges. They provide immunity to various types of infections but may also contribute to organ homeostasis as they produce f…
A catch-22: Interleukin-22 and cancer.
Barrier surfaces of multicellular organisms are in constant contact with the environment and infractions to the integrity of epithelial surfaces is likely a frequent event. Interestingly, components of the immune system, that can be activated by environmental compounds such as the microbiota or nutrients, are interspersed among epithelial cells or directly underlie the epithelium. It is now appreciated that immune cells continuously receive and integrate signals from the environment. Curiously, such continuous reception of stimulation does not normally trigger an inflammatory response but mediators produced by immune cells in response to such signals seem to rather promote barrier integrity…
CD14 is a key organizer of microglial responses to CNS infection and injury
Microglia, innate immune cells of the CNS, sense infection and damage through overlapping receptor sets. Toll-like receptor (TLR) 4 recognizes bacterial lipopolysaccharide (LPS) and multiple injury-associated factors. We show that its co-receptor CD14 serves three non-redundant functions in microglia. First, it confers an up to 100-fold higher LPS sensitivity compared to peripheral macrophages to enable efficient proinflammatory cytokine induction. Second, CD14 prevents excessive responses to massive LPS challenges via an interferon β-mediated feedback. Third, CD14 is mandatory for microglial reactions to tissue damage-associated signals. In mice, these functions are essential for balanced …
Group 3 Innate Lymphoid Cells Program a Distinct Subset of IL-22BP-Producing Dendritic Cells Demarcating Solitary Intestinal Lymphoid Tissues.
Solitary intestinal lymphoid tissues such as cryptopatches (CPs) and isolated lymphoid follicles (ILFs) constitute steady-state activation hubs containing group 3 innate lymphoid cells (ILC3) that continuously produce interleukin (IL)-22. The outer surface of CPs and ILFs is demarcated by a poorly characterized population of CD11c+ cells. Using genome-wide single-cell transcriptional profiling of intestinal mononuclear phagocytes and multidimensional flow cytometry, we found that CP- and ILF-associated CD11c+ cells were a transcriptionally distinct subset of intestinal cDCs, which we term CIA-DCs. CIA-DCs required programming by CP- and ILF-resident CCR6+ ILC3 via lymphotoxin-β receptor sig…
Interleukin-12 and -23 Control Plasticity of CD127(+) Group 1 and Group 3 Innate Lymphoid Cells in the Intestinal Lamina Propria.
Human group 1 ILCs consist of at least three phenotypically distinct subsets, including NK cells, CD127(+) ILC1, and intraepithelial CD103(+) ILC1. In inflamed intestinal tissues from Crohn's disease patients, numbers of CD127(+) ILC1 increased at the cost of ILC3. Here we found that differentiation of ILC3 to CD127(+) ILC1 is reversible in vitro and in vivo. CD127(+) ILC1 differentiated to ILC3 in the presence of interleukin-2 (IL-2), IL-23, and IL-1β dependent on the transcription factor RORγt, and this process was enhanced in the presence of retinoic acid. Furthermore, we observed in resection specimen from Crohn's disease patients a higher proportion of CD14(+) dendritic cells (DC), whi…
Innate lymphoid cells, precursors and plasticity
Innate lymphoid cells (ILC) have only recently been recognized as a separate entity of the lymphoid lineage. Their subpopulations share common characteristics in terms of early development and major transcriptional circuitry with their related cousins of the T cell world. It is currently hypothesized that ILCs constitute an evolutionary older version of the lymphoid immune system. They are found at all primary entry points for pathogens such as mucosal surfaces of the lung and gastrointestinal system, the skin and the liver, which is the central contact point for pathogens that breach the intestinal barrier and enter the circulation. There, ILC contribute to the first line defense as well a…
Tuft cell‐derived IL‐25 activates and maintains ILC2
Parasitic helminths and allergens induce a type 2 immune response leading to profound changes in tissue physiology, including hyperplasia of mucus-secreting goblet cells1 and smooth muscle hypercontractility2. This response, known as ‘weep and sweep’, requires interleukin (IL)-13 production by tissue-resident group 2 innate lymphoid cells (ILC2s) and recruited type 2 helper T cells (TH2 cells)3. Experiments in mice and humans have demonstrated requirements for the epithelial cytokines IL-33, thymic stromal lymphopoietin (TSLP) and IL-25 in the activation of ILC2s4–11, but the sources and regulation of these signals remain poorly defined. In the small intestine, the epithelium consists of at…
Interferon-λ and interleukin 22 act synergistically for the induction of interferon-stimulated genes and control of rotavirus infection.
The epithelium is the main entry point for many viruses, but the processes that protect barrier surfaces against viral infections are incompletely understood. Here we identified interleukin 22 (IL-22) produced by innate lymphoid cell group 3 (ILC3) as an amplifier of signaling via interferon-λ (IFN-λ), a synergism needed to curtail the replication of rotavirus, the leading cause of childhood gastroenteritis. Cooperation between the receptor for IL-22 and the receptor for IFN-λ, both of which were 'preferentially' expressed by intestinal epithelial cells (IECs), was required for optimal activation of the transcription factor STAT1 and expression of interferon-stimulated genes (ISGs). These d…
A murine intestinal intraepithelial NKp46-negative innate lymphoid cell population characterized by group 1 properties
The Ly49E receptor is preferentially expressed on murine innate-like lymphocytes, such as epidermal Vγ3 T cells, intestinal intraepithelial CD8αα(+) T lymphocytes, and CD49a(+) liver natural killer (NK) cells. As the latter have recently been shown to be distinct from conventional NK cells and have innate lymphoid cell type 1 (ILC1) properties, we investigated Ly49E expression on intestinal ILC populations. Here, we show that Ly49E expression is very low on known ILC populations, but it can be used to define a previously unrecognized intraepithelial innate lymphoid population. This Ly49E-positive population is negative for NKp46 and CD8αα, expresses CD49a and CD103, and requires T-bet expre…
Innate immunity repairs gut lining
It emerges that innate immune cells called group 3 innate lymphoid cells signal directly to intestinal stem cells to promote the replacement of damaged epithelial cells lining the gut. See Letter p.560 The cellular signals supporting normal epithelial intestine maintenance through regulation of intestinal stem cell (ISC) activity are well characterized, but the signals involved in the regulation of the ISC compartment after damage are still unclear. Alan Hanash and colleagues have found that innate lymphoid cells produce interleukin-22 (IL-22) after injury to increase the growth of mouse intestinal organoids. They further show that recombinant IL-22 promotes ISC expansion in both human and …