Rudi W. Hendriks

Pulmonary innate lymphoid cells are major producers of IL-5 and IL-13 in murine models of allergic asthma.

Allergic asthma is characterized by chronic airway inflammation and hyperreactivity and is thought to be mediated by an adaptive T helper‐2 (Th2) cell‐type immune resp‐onse. Here, we demonstrate that type 2 pulmonary innate lymphoid cells (ILC2s) significantly contribute to production of the key cytokines IL‐5 and IL‐13 in experimental asthma. In naive mice, lineage‐marker negative ILC2s expressing IL‐7Rα, CD25, Sca‐1, and T1/ST2(IL‐33R) were present in lungs and mediastinal lymph nodes (MedLNs), but not in broncho‐alveolar lavage (BAL) fluid. Upon intranasal administration of IL‐25 or IL‐33, an asthma phenotype was induced, whereby ILC2s accumulated in lungs, MedLNs, and BAL fluid. After IL‐25 and IL‐33 administration, ILC2s constituted ∼50 and ∼80% of IL‐5+/IL‐13+ cells in lung and BAL, respectively. Also in house dust mite‐induced or ovalbumin‐induced allergic asthma, the ILC2 population in lung and BAL fluid increased significantly in size and ILC2s were a major source of IL‐5 or IL‐13. Particularly in OVA‐induced asthma, the contribution of ILC2s to the total population of intracellular IL‐5+ and IL‐13+ cells in the lung was in the same range as found for Th2 cells. We conclude that both ILC2s and Th2 cells produce large amounts of IL‐5 and IL‐13 that contribute to allergic airway inflammation.

GATA-2 plays two functionally distinct roles during the ontogeny of hematopoietic stem cells.

GATA-2 is an essential transcription factor in the hematopoietic system that is expressed in hematopoietic stem cells (HSCs) and progenitors. Complete deficiency of GATA-2 in the mouse leads to severe anemia and embryonic lethality. The role of GATA-2 and dosage effects of this transcription factor in HSC development within the embryo and adult are largely unexplored. Here we examined the effects of GATA-2 gene dosage on the generation and expansion of HSCs in several hematopoietic sites throughout mouse development. We show that a haploid dose of GATA-2 severely reduces production and expansion of HSCs specifically in the aorta-gonad-mesonephros region (which autonomously generates the first HSCs), whereas quantitative reduction of HSCs is minimal or unchanged in yolk sac, fetal liver, and adult bone marrow. However, HSCs in all these ontogenically distinct anatomical sites are qualitatively defective in serial or competitive transplantation assays. Also, cytotoxic drug-induced regeneration studies show a clear GATA-2 dose–related proliferation defect in adult bone marrow. Thus, GATA-2 plays at least two functionally distinct roles during ontogeny of HSCs: the production and expansion of HSCs in the aorta-gonad-mesonephros and the proliferation of HSCs in the adult bone marrow.

Dendritic cells are crucial for maintenance of tertiary lymphoid structures in the lung of influenza virus–infected mice

Tertiary lymphoid organs (TLOs) are organized aggregates of B and T cells formed in postembryonic life in response to chronic immune responses to infectious agents or self-antigens. Although CD11c+ dendritic cells (DCs) are consistently found in regions of TLO, their contribution to TLO organization has not been studied in detail. We found that CD11chi DCs are essential for the maintenance of inducible bronchus-associated lymphoid tissue (iBALT), a form of TLO induced in the lungs after influenza virus infection. Elimination of DCs after the virus had been cleared from the lung resulted in iBALT disintegration and reduction in germinal center (GC) reactions, which led to significantly reduced numbers of class-switched plasma cells in the lung and bone marrow and reduction in protective antiviral serum immunoglobulins. Mechanistically, DCs isolated from the lungs of mice with iBALT no longer presented viral antigens to T cells but were a source of lymphotoxin (LT) β and homeostatic chemokines (CXCL-12 and -13 and CCL-19 and -21) known to contribute to TLO organization. Like depletion of DCs, blockade of LTβ receptor signaling after virus clearance led to disintegration of iBALT and GC reactions. Together, our data reveal a previously unappreciated function of lung DCs in iBALT homeostasis and humoral immunity to influenza virus.

Targeting Bruton's tyrosine kinase in B cell malignancies

Brutons tyrosine kinase (BTK) is a key component of B cell receptor (BCR) signalling and functions as an important regulator of cell proliferation and cell survival in various B cell malignancies. Small-molecule inhibitors of BTK have shown antitumour activity in animal models and, recently, in clinical studies. High response rates were reported in patients with chronic lymphocytic leukaemia and mantle cell lymphoma. Remarkably, BTK inhibitors have molecular effects that cannot be explained by the classic role of BTK in BCR signalling. In this Review, we highlight the importance of BTK in various signalling pathways in the context of its therapeutic inhibition.

COX-2 inhibition improves immunotherapy and is associated with decreased numbers of myeloid-derived suppressor cells in mesothelioma. Celecoxib influences MDSC function

BackgroundMyeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature cells that accumulates in tumour-bearing hosts. These cells are induced by tumour-derived factors (e.g. prostaglandins) and have a critical role in immune suppression. MDSC suppress T and NK cell function via increased expression of arginase I and production of reactive oxygen species (ROS) and nitric oxide (NO). Immune suppression by MDSC was found to be one of the main factors for immunotherapy insufficiency. Here we investigate if the in vivo immunoregulatory function of MDSC can be reversed by inhibiting prostaglandin synthesis by specific COX-2 inhibition focussing on ROS production by MDSC subtypes. In addition, we determined if dietary celecoxib treatment leads to refinement of immunotherapeutic strategies.MethodsMDSC numbers and function were analysed during tumour progression in a murine model for mesothelioma. Mice were inoculated with mesothelioma tumour cells and treated with cyclooxygenase-2 (COX-2) inhibitor celecoxib, either as single agent or in combination with dendritic cell-based immunotherapy.ResultsWe found that large numbers of infiltrating MDSC co-localise with COX-2 expression in those areas where tumour growth takes place. Celecoxib reduced prostaglandin E2 levels in vitro and in vivo. Treatment of tumour-bearing mice with dietary celecoxib prevented the local and systemic expansion of all MDSC subtypes. The function of MDSC was impaired as was noticed by reduced levels of ROS and NO and reversal of T cell tolerance; resulting in refinement of immunotherapy.ConclusionsWe conclude that celecoxib is a powerful tool to improve dendritic cell-based immunotherapy and is associated with a reduction in the numbers and suppressive function of MDSC. These data suggest that immunotherapy approaches benefit from simultaneously blocking cyclooxygenase-2 activity.

Gata3 drives development of RORγt+ group 3 innate lymphoid cells

The transcription factor Gata3 is required for the generation of group 3 innate lymphoid cells (ILC3) that protect mucosal surfaces.

Essential, dose-dependent role for the transcription factor Gata3 in the development of IL-5+ and IL-13+ type 2 innate lymphoid cells

Group 2 innate lymphoid cells (ILC2s; also called nuocytes, innate helper cells, or natural helper cells) provide protective immunity during helminth infection and play an important role in influenza-induced and allergic airway hyperreactivity. Whereas the transcription factor GATA binding protein 3 (Gata3) is important for the production of IL-5 and -13 by ILC2s in response to IL-33 or -25 stimulation, it is not known whether Gata3 is required for ILC2 development from hematopoietic stem cells. Here, we show that chimeric mice generated with Gata3-deficient fetal liver hematopoietic stem cells fail to develop systemically dispersed ILC2s. In these chimeric mice, in vivo administration of IL-33 or -25 fails to expand ILC2 numbers or to induce characteristic ILC2-dependent IL-5 or -13 production. Moreover, cell-intrinsic Gata3 expression is required for ILC2 development in vitro and in vivo. Using mutant and transgenic mice in which Gata3 gene copy number is altered, we show that ILC2 generation from common lymphoid progenitors, as well as ILC2 homeostasis and cytokine production, is regulated by Gata3 expression levels in a dose-dependent fashion. Collectively, these results identify Gata3 as a critical early regulator of ILC2 development, thereby extending the paradigm of Gata3-dependent control of type 2 immunity to include both innate and adaptive lymphocytes.

CTCF regulates cell cycle progression of αβ T cells in the thymus

The 11‐zinc finger protein CCCTC‐binding factor (CTCF) is a highly conserved protein, involved in imprinting, long‐range chromatin interactions and transcription. To investigate its function in vivo, we generated mice with a conditional Ctcf knockout allele. Consistent with a previous report, we find that ubiquitous ablation of the Ctcf gene results in early embryonic lethality. Tissue‐specific inactivation of CTCF in thymocytes specifically hampers the differentiation of αβ T cells and causes accumulation of late double‐negative and immature single‐positive cells in the thymus of mice. These cells are normally large and actively cycling, and contain elevated amounts of CTCF. In Ctcf knockout animals, however, these cells are small and blocked in the cell cycle due to increased expression of the cyclin‐CDK inhibitors p21 and p27. Taken together, our results show that CTCF is required in a dose‐dependent manner and is involved in cell cycle progression of αβ T cells in the thymus. We propose that CTCF positively regulates cell growth in rapidly dividing thymocytes so that appropriate number of cells are generated before positive and negative selection in the thymus.

An intrinsic but cell-nonautonomous defect in GATA-1-overexpressing mouse erythroid cells

GATA-1 is a tissue-specific transcription factor that is essential for the production of red blood cells. Here we show that overexpression of GATA-1 in erythroid cells inhibits their differentiation, leading to a lethal anaemia. Using chromosome-X-inactivation of a GATA-1 transgene and chimaeric animals, we show that this defect is intrinsic to erythroid cells, but nevertheless cell nonautonomous. Usually, cell nonautonomy is thought to reflect aberrant gene function in cells other than those that exhibit the phenotype. On the basis of our data, we propose an alternative mechanism in which a signal originating from wild-type erythroid cells restores normal differentiation to cells overexpressing GATA-1 in vivo. The existence of such a signalling mechanism indicates that previous interpretations of cell-nonautonomous defects may be erroneous in some cases and may in fact assign gene function to incorrect cell types.

GATA-3 Function in Innate and Adaptive Immunity

The zinc-finger transcription factor GATA-3 has received much attention as a master regulator of T helper 2 (Th2) cell differentiation, during which it controls interleukin-4 (IL-4), IL-5, and IL-13 expression. More recently, GATA-3 was shown to contribute to type 2 immunity through regulation of group 2 innate lymphoid cell (ILC2) development and function. Furthermore, during thymopoiesis, GATA-3 represses B cell potential in early T cell precursors, activates TCR signaling in pre-T cells, and promotes the CD4(+) T cell lineage after positive selection. GATA-3 also functions outside the thymus in hematopoietic stem cells, regulatory T cells, CD8(+) T cells, thymic natural killer cells, and ILC precursors. Here we discuss the varied functions of GATA-3 in innate and adaptive immune cells, with emphasis on its activity in T cells and ILCs, and examine the mechanistic basis for the dose-dependent, developmental-stage- and cell-lineage-specific activity of this transcription factor.