Reduced expression of IL-12 receptor beta2 and IL-18 receptor alpha genes in natural killer cells and macrophages derived from B6-mi/mi mice

Effect of Momordica charantia polysaccharide on immunomodulatory activity in mice

Momordica charantia polysaccharides (MCPs) have been reported to exert beneficial roles, such as disease healing, in medicine and pharmacy. However, little is known about their effects on immunomodulation. The present study aimed to explore the possible effects of Momordica charantia polysaccharide (MCP) on the immunomodulatory activity of mice lymphocytes. To this aim, male BALB/c mice aged 6-8 weeks were assigned to the following six experimental groups: i) Normal (NG); ii) model (MG); iii) positive (PG); iv) MCP low-dose (MLG); v) MCP medium-dose (MMG); and vi) MCP high-dose (MHG). An immunosuppressive model was established by the intraperitoneal injection of cyclophosphamide in all groups apart from NG. The NG and MG mice were fed with distilled water, whereas the PG mice were administered with levamisole and the MLG, MMG and MHG mice were fed on low, medium and high (100, 200 and 300 mg/kg, respectively) doses of MCP for 21 consecutive days. Subsequently, the mice underwent surgical procedure and were analysed using a range of procedures, including measurement of the thymus index (TI) and spleen index (SI), assessment of the lymphocyte proliferation rate and cell phagocytosis of peritoneal macrophages, lymphocyte proliferation, secretion and mRNA expression of cytokines IFN-γ, IL-6 and IL-12. The mice divided into six groups as mentioned above and treated for 7 days, in the first 6 days, except NG group, mice in each group were desiccated in the abdominal cavity and sensitized by 1% dinitrofluorobenzene (DNFB). On day 6, mice were sensitized with 20 µl DNFB/acetone/olive oil solution behind the right ear and in front of the right ear. Compared with those in the NG mice (not injected with 80 mg/kg cyclophosphamide), the TIs and SIs of the PG, MLG, MMG and MHG mice were increased. In addition, the inhibitory rate of ear swelling and the phagocytic activity of peritoneal macrophages in the PG, MLG, MMG and MHG mice were increased compared with those of MG. Furthermore, the lymphocyte proliferation rate, the secretion and relative mRNA expression levels of cytokines IFN-γ, IL-6 and IL-12 were significantly increased in the PG, MMG and MHG mice compared with those in the NG mice. The results from the present study suggest that treatment with MCP led to an upregulation of the organ indices of immunosuppressed mice, reduced their delayed allergic reaction indicated by the differential cytokine levels, improved the phagocytic activity of peritoneal macrophages, enhanced the proliferation rate of lymphocytes, increased the secretion and expression of IFN-γ, IL-6 and IL-12. Therefore, MCP may improve the immune function of the immunosuppressed mice.

The underestimated role of the microphthalmia-associated transcription factor (MiTF) in normal and pathological haematopoiesis

Haematopoiesis, the process by which a restrained population of stem cells terminally differentiates into specific types of blood cells, depends on the tightly regulated temporospatial activity of several transcription factors (TFs). The deregulation of their activity or expression is a main cause of pathological haematopoiesis, leading to bone marrow failure (BMF), anaemia and leukaemia. TFs can be induced and/or activated by different stimuli, to which they respond by regulating the expression of genes and gene networks. Most TFs are highly pleiotropic; i.e., they are capable of influencing two or more apparently unrelated phenotypic traits, and the action of a single TF in a specific setting often depends on its interaction with other TFs and signalling pathway components. The microphthalmia-associated TF (MiTF) is a prototype TF in multiple situations. MiTF has been described extensively as a key regulator of melanocyte and melanoma development because it acts mainly as an oncogene. Mitf-mutated mice show a plethora of pleiotropic phenotypes, such as microphthalmia, deafness, abnormal pigmentation, retinal degeneration, reduced mast cell numbers and osteopetrosis, revealing a greater requirement for MiTF activity in cells and tissue. A growing amount of evidence has led to the delineation of key roles for MiTF in haematopoiesis and/or in cells of haematopoietic origin, including haematopoietic stem cells, mast cells, NK cells, basophiles, B cells and osteoclasts. This review summarizes several roles of MiTF in cells of the haematopoietic system and how MiTFs can impact BM development.

Development and maturation of natural killer cells

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.

Transcriptional and post-transcriptional regulation of NK cell development and function

Natural killer (NK) cells are specialized innate lymphoid cells that survey against viral infections and malignancy. Numerous advances have improved our understanding of the molecular mechanisms that control NK cell development and function over the past decade. These include both studies on the regulatory effects of transcription factors and translational repression via microRNAs. In this review, we summarize our current knowledge of DNA-binding transcription factors that regulate gene expression and thereby orchestrate NK cell development and activation, with an emphasis on recent discoveries. Additionally, we highlight our understanding of how RNA-binding microRNAs fine tune the NK cell molecular program. We also underscore the large number of open questions in the field that are now being addressed using new technological approaches and genetically engineered model organisms. Ultimately, a deeper understanding of the basic molecular biology of NK cells will facilitate new strategies to manipulate NK cells for the treatment of human disease.

IL-18 contributes to susceptibility to Leishmania amazonensis infection by macrophage-independent mechanisms

We evaluated the role of IL-18 during Leishmania amazonensis infection in C57BL/6 mice, using IL-18KO mice. We showed that IL-18 is involved in susceptibility to L. amazonensis, since IL-18KO mice presented reduced lesions and parasite loads. Because macrophages are the host cells of the parasite, we investigated if macrophages were involved in IL-18-mediated susceptibility to L. amazonensis. We showed that macrophages obtained from WT or IL-18KO responded similarly to L. amazonensis infection. Moreover, we showed that C57BL/6 macrophages do not respond to IL-18, since they do not express IL-18R. Therefore, macrophages are not involved in IL-18-mediated susceptibility to L. amazonensis.

Transcriptional Control of NK Cells

Natural killer (NK) cells are innate lymphocytes that survey the environment and protect the host from infected and cancerous cells. As their name implies, NK cells represent an early line of defense during pathogen invasion by directly killing infected cells and secreting inflammatory cytokines. Although the function of NK cells was first described more than four decades ago, the development of this cytotoxic lineage is not well understood. In recent years, we have begun to identify specific transcription factors that control each stage of development and maturation, from ontogeny of the NK cell progenitor to the effector functions of activated NK cells in peripheral organs. This chapter highlights the transcription factors that are unique to NK cells, or shared between NK cells and other hematopoietic cell lineages, but govern the biology of this cytolytic lymphocyte.

TGF-β is responsible for NK cell immaturity during ontogeny and increased susceptibility to infection during mouse infancy

A major gap in our understanding of infant immunity is why natural killer (NK) cellresponses are deficient, making infants more prone to viral infection. Here we demonstrate that transforming growth factor-β (TGF-β) was responsible for NK cell immaturity during infancy. Higher numbers of fully mature NK cells were found in CD11c^dnR mice, whose NK cells lack TGF-βR signaling. Importantly, ontogenic maturation of NK cells progressed faster in the absence of TGF-β signaling, resulting in the formation of mature NK cell pool early in life. As a consequence, infant CD11c^dnR mice efficiently controlled viral infections. These data thus demonstrate an unprecedented role for TGF-β in ontogeny that can explain why NK cell responses are deficient early in life.

Enhancement of neutrophil function by interleukin-18 therapy protects burn-injured mice from methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a grave concern in burn-injured patients. We investigated the efficacy of interleukin-18 (IL-18) treatment in postburn MRSA infection. Alternate-day injections of IL-18 into burn-injured C57BL/6 mice significantly increased their survival after MRSA infection and after methicillin-sensitive S. aureus infection. Although IL-18 treatment of burn-injured mice augmented natural IgM production before MRSA infection and gamma interferon (IFN-γ) production after MRSA infection, neither IgM nor IFN-γ significantly contributed to the improvement in mouse survival. IL-18 treatment increased/restored the serum tumor necrosis factor (TNF), IL-17, IL-23, granulocyte colony-stimulating factor (G-CSF), and macrophage inflammatory protein (MIP-2) levels, as well as the neutrophil count, after MRSA infection of burn-injured mice; it also improved impaired neutrophil functions, phagocytic activity, production of reactive oxygen species, and MRSA-killing activity. However, IL-18 treatment was ineffective against MRSA infection in both burn- and sham-injured neutropenic mice. Enhancement of neutrophil functions by IL-18 was also observed in vitro. Furthermore, when neutrophils from IL-18-treated burn-injured mice were adoptively transferred into nontreated burn-injured mice 2 days after MRSA challenge, survival of the recipient mice increased. NOD-SCID mice that have functionally intact neutrophils and macrophages (but not T, B, or NK cells) were substantially resistant to MRSA infection. IL-18 treatment increased the survival of NOD-SCID mice after burn injury and MRSA infection. An adoptive transfer of neutrophils using NOD-SCID mice also showed a beneficial effect of IL-18-activated neutrophils, similar to that seen in C57BL/6 mice. Thus, although neutrophil functions were impaired in burn-injured mice, IL-18 therapy markedly activated neutrophil functions, thereby increasing survival from postburn MRSA infection.

Transcriptional control of natural killer cell development and function

Natural killer (NK) cells play an important role in host defense against tumors and viruses and other infectious diseases. NK cell development is regulated by mechanisms that are both shared with and separate from other hematopoietic cell lineages. Functionally, NK cells use activating and inhibitory receptors to recognize both healthy and altered cells such as transformed or infected cells. Upon activation, NK cells produce cytokines and cytotoxic granules using mechanisms similar to other hematopoietic cell lineages especially cytotoxic T cells. Here we review the transcription factors that control NK cell development and function. Although many of these transcription factors are shared with other hematopoietic cell lineages, they control unexpected and unique aspects of NK cell biology. We review the mechanisms and target genes by which these transcriptional regulators control NK cell development and functional activity.

Ionizing radiation stimulates secretion of pro-inflammatory cytokines: dose-response relationship, mechanisms and implications

In previous studies we showed a marked increase in secretion of inflammatory cytokines TNFalpha and interleukin (IL)-1beta by mouse macrophages in response to different doses of ionizing radiation (IR). Here we show the stimulation of IL-12 and IL-18 secretion by mouse peritoneal macrophages after whole-body irradiation with exploration of the possible mechanisms and implications in cancer radiotherapy. Both low (0.075 Gy) and high (2 Gy) doses of IR were found to cause sustained stimulation of IL-12 and IL-18 secretion by mouse macrophages; this paralleled the activation of NF-kappaB as well as up-regulated expression of CD14 and TLR4-MD2 on the macrophage surface and MyD88 in the cytoplasm. The expression of CD14, TLR4-MD2 and MyD88 increased in a dose-dependent manner from radiation doses between 0.05 and 2 Gy. The secretion of IL-12 and IL-18 showed a dose-dependent increase from doses between 0.05 and 4 Gy. It is concluded that IR can stimulate the secretion of IL-12 and IL-18 presumably via activation of the Toll signaling pathway in macrophages. The potential harmful effect of repeated doses of radiation used in radiotherapy for certain cancers is discussed.

Treatment of monocytes with interleukin (IL)-12 plus IL-18 stimulates survival, differentiation and the production of CXC chemokine ligands (CXCL)8, CXCL9 and CXCL10

During inflammation, interleukin (IL)-12 and IL-18 are produced by macrophages and other cell types such as neutrophils (IL-12), keratinocytes and damaged endothelial cells (IL-18). To explore the role of IL-12 and IL-18 in inflammatory innate immune responses we investigated their impact on human peripheral blood monocytes and mature bronchoalveolar lavage (BAL) macrophages. IL-12 and IL-18 together, but not alone, prevented spontaneous apoptosis of cultured monocytes, promoted monocyte clustering and subsequent differentiation into macrophages. These morphological changes were accompanied by increased secretion of CXC chemokine ligands (CXCL)9, CXCL10 (up to 100-fold, P < 0.001) and CXCL8 (up to 10-fold, P < 0.001) but not CCL3, CCL4 or CCL5. Mature macrophages (from BALs) expressed high basal levels of CXCL8, that were no modified upon stimulation with IL-12 and IL-18. In contrast, the basal production of CXCL9 and CXCL10 by BALs was increased by 10-fold (P < 0.001) in the presence of either IL-12 or IL-18 alone and by 50-fold in the presence of both cytokines. In conclusion, our results indicate a relevant role for IL-12 and IL-18 in the activation and resolution of inflammatory immune responses, by increasing the survival of monocytes and by inducing the production of chemokines. In particular, those that may regulate angiogenesis and promote the recruitment of monocytes, activated T cells (CXCL9 and CXCL10) and granulocytes (CXCL8).