Role of innate lymphocytes in infection and inflammation

Evaluation of the T helper 17 cell specific genes and the innate lymphoid cells counts in the peripheral blood of patients with the common variable immunodeficiency

BACKGROUND

Common variable immunodeficiency (CVID) is characterized by a deficiency in the immune system with a heterogeneous collection of disorders resulting in antibody deficiency and recurrent infections. T helper 17 (Th17) cells promote B-cell survival and synergize with the B-cell activating factor to induce their differentiation into the plasma cells. A sub-population of innate lymphoid cells (ILCs) also produces interleukin 17 (IL-17). This study aimed to measure the Th17 specific genes and ILCs counts in the CVID patients in comparison with control subjects.

MATERIALS AND METHODS

Total messenger ribonucleic acid (mRNA) was extracted from the whole blood samples of 10 CVID patients and 10 healthy individuals. IL-17, retinoic acid receptor-related orphan receptor C2 (RORC2), IL-23R, and IL-9 gene expression were measured using the quantitative reverse transcriptase-polymerase chain reaction. Count of lineage negative/CD127(+)/CD90(+) ILCs in the blood samples was performed by the flow cytometry method.

RESULTS

The transcript levels of IL-17 and RORC2 in CVID patients was strongly lower than control subjects (P = 0.049 and P = 0.046, respectively), but slight reduction in the IL-23R expression (P = 0.252) have seen in the CVID patients. Accordingly, the number of ILCs decreased significantly (P = 0.04). Interestingly, IL-9 mRNA level was more significantly in the CVID patients (P = 0.001).

CONCLUSION

The results presented in this study show that the Th17 cell specific genes expression (as the determiner Th17 cells) and ILCs (another lymphoid source of IL-17) are decreased in patients with CVID and this could be an explanation for the defect of their humoral immune response. In addition, elevation of the IL-9 gene expression may shed a new light into the way toward the understanding of the mechanism of autoimmunity in the CVID patients.

Functional aspects of fish lymphocytes

After almost 40 years of studies in comparative immunology, some light has been shed on the evolutive immunobiology of vertebrates, and experimental evidences have shown that acquired immunity, defined by somatic recombination of antigen-binding molecules and memory, is an achievement as ancient as jawless vertebrates. However, the molecular processes generating antigen receptors evolved independently between jawless and jawed fishes, and produced lymphocytic cells with similar functions but employing different sets of genes. In recent years, data have been provided describing some in vitro and in vivo functional responses of fish lymphocytes. After a long gap, the number of specific markers for fish lymphocytes is increasing, thus allowing a first characterisation of lymphocyte subsets. Overall, in the near future it will be possible to open a new chapter in fish immunology and investigate functional immunity of lymphocyte responses by combining the extensive knowledge on immune gene products with markers for molecules and cells. The present review summarizes current knowledge on functional features of fish lymphocytes.

Increased cytokine/chemokines in serum from asthmatic and non-asthmatic patients with viral respiratory infection

BACKGROUND

Respiratory viral infections can induce different cytokine/chemokine profiles in lung tissues and have a significant influence on patients with asthma. There is little information about the systemic cytokine status in viral respiratory-infected asthmatic patients compared with non-asthmatic patients.

OBJECTIVES

The aim of this study was to determine changes in circulating cytokines (IL-1β, TNF-α, IL-4, IL-5) and chemokines (MCP1: monocyte chemoattractant protein-1 and RANTES: regulated on activation normal T cell expressed and secreted) in patients with an asthmatic versus a non-asthmatic background with respiratory syncytial virus, parainfluenza virus or adenovirus respiratory infection. In addition, human monocyte cultures were incubated with respiratory viruses to determine the cytokine/chemokine profiles.

PATIENTS/METHODS

Patients with asthmatic (n = 34) and non-asthmatic (n = 18) history and respiratory infections with respiratory syncytial virus, parainfluenza, and adenovirus were studied. Healthy individuals with similar age and sex (n = 10) were used as controls. Cytokine/chemokine content in blood and culture supernatants was determined by ELISA. Monocytes were isolated by Hystopaque gradient and cocultured with each of the above-mentioned viruses.

RESULTS

Similar increased cytokine concentrations were observed in asthmatic and non-asthmatic patients. However, higher concentrations of chemokines were observed in asthmatic patients. Virus-infected monocyte cultures showed similar cytokine/chemokine profiles to those observed in the patients.

CONCLUSIONS

Circulating cytokine profiles induced by acute viral lung infection were not related to asthmatic status, except for chemokines that were already increased in the asthmatic status. Monocytes could play an important role in the increased circulating concentration of cytokines found during respiratory viral infections.

Critical role of p38 and GATA3 in natural helper cell function

Natural helper (NH) cells, a member of Lin(-)IL-2R(+)IL-7R(+)IL-25R(+)IL-33R(+)GATA3(+) group 2 innate lymphoid cell subset, are characterized by the expression of transcription factors GATA3 and RORα and production of large amounts of Th2 cytokines such as IL-5, IL-6, and IL-13 upon IL-33 stimulation or a combination of IL-2 and IL-25. We have studied the signal transduction pathways critical for the cytokine expression and development of NH cell. Either stimulation with IL-33 or a combination of IL-2 and IL-25 induced p38 activation and phosphorylation of GATA3 in NH cells, and the phosphorylated form of GATA3 bound to the IL-5 and IL-13 promoters. All these events were blocked by SB203580, a p38 inhibitor. Inhibition of p38 also blocked IL-6 production. The mature NH cells lacking Gata3 were impaired in the proliferation and production of IL-5 and IL-13, but not IL-6, indicating that both p38 and GATA3 are critical for the proliferation and production of IL-5 and IL-13 and that the mechanisms downstream of p38 differ between IL-6 and IL-5/IL-13. In contrast, the NH cells lacking RORα showed no impairment in the proliferation and cytokine production, indicating that GATA3 but not RORα plays a pivotal role in the effector functions of mature NH cell. However, deletion of either GATA3 or RORα in hematopoietic stem cells severely blocked the development into NH cells. Our results demonstrate the important roles of p38 and GATA3 in NH cell functions.

Interleukin-7 expression in tears and orbital tissues of patients with Graves' ophthalmopathy

The aim of this study was to explore whether IL-7 participates in the pathogenesis of Graves' ophthalmopathy (GO). This was a prospective study. 20 GO patients (40 eyes) and 20 healthy volunteers (40 eyes) were recruited. The tear concentration of IL-7 was measured using ELISA assay. IL-7 expression in orbital tissues was evaluated by immunohistochemistry. Patients with inactive GO had the highest IL-7 concentrations in the tears, followed by healthy controls and patients with active GO per ELISA. Immunohistochemistry analysis showed that IL-7 expression in orbital tissues of the inactive GO samples was higher than that of the volunteers. Changes of IL-7 expression in different phases of GO suggested that IL-7 may play an important role in the pathogenesis of GO.

IFN-γ production by CD27⁺ NK cells exacerbates Listeria monocytogenes infection in mice by inhibiting granulocyte mobilization

Natural killer (NK) cells are key components of the immune system involved in several immune reactions, including the clearance of intracellular pathogens. When activated, NK cells rapidly secrete particular cytokines that activate innate immunity and facilitate development of adaptive responses. Conflicting reports on the role of NK cells during infection by Listeria monocytogenes can be found in the literature. Here, we demonstrate that during lethal infection by L. monocytogenes, activation of NK cells via the costimulatory molecule CD27 leads to excessive IFN-γ production. This impairs innate anti-bacterial host defenses by inducing downregulation of CXCR2 on granulocytes and consequently inhibiting their recruitment to the sites of infection. The use of antibodies to block CD27 signaling or to deplete IFN-γ was sufficient to rescue mice from lethal challenge by L. monocytogenes. Our findings contribute to a better understanding of the importance of CD27 signaling in activation of NK cells and should provide new ways of interfering with infections.

Th2-type innate immune responses mediated by natural helper cells

Natural helper (NH) cells are a newly identified innate lymphocyte population that responds to a combination of interleukin (IL)-2 and either IL-25 or IL-33 to produce large amounts of T helper cell type 2 (Th2) cytokines. NH cells have been identified in fat-associated lymphoid clusters (FALCs), produce Th2 cytokines constitutively without any stimulation, and support the self-renewal of B1 cells and IgA production by B cells. Large amounts of IL-5 and IL-13 produced upon helminth infection or in response to IL-33 can induce eosinophilia and goblet cell hyperplasia in the lung and intestine; these cytokines, which activate NH cells, play important roles in antihelminth immunity and allergic diseases such as asthma.

Role of mast cells in mucosal diseases: current concepts and strategies for treatment

Mast cells are well known for their role in type I hypersensitivity. However, their role in the immune system as well as their pathophysiological role in other diseases is underacknowledged. The role of mast cells in inflammatory bowel disease, allergic contact dermatitis and asthma is illustrated in this review. The contribution of mast cell activation in these diseases is controversial and two alternative means are proposed: activation via stress response pathways and immunoglobulin-free light chains. Activation of the mast cells leads to release of preformed mediators and to generation of other potent biological substances that have both physiological and pathophysiological effects. The role of these mediators in the aforementioned diseases is also outlined in this review. When the roles of mast cells are better understood, drugs specifically targeting mast cells may be developed to effectively treat a wide range of diseases.

IL-22 in tissue-protective therapy

IL-22, a member of the IL-10 cytokine family, has recently gained significant attention as a protective agent in murine models of diseases driven by epithelial injury. Like its biochemical and functional sibling IL-10, IL-22 elicits cellular activation primarily by engaging the STAT3 signalling pathway. Exclusively produced by leukocytes, but targeting mostly cells of epithelial origin, IL-22 has been proposed as a specialized cytokine messenger acting between leukocytic and non-leukocytic cell compartments. A lack of response in leukocytes to IL-22 mirrors tightly controlled IL-22 receptor expression and probably explains the apparent lack of instant adverse effects after systemic IL-22 administration to mice. Anti-apoptotic, pro-proliferative and pro-regenerative characteristics the major biological properties of this cytokine. Specifically, application of IL-22 is associated with tissue protection and/or regeneration in murine models of infection/microbe-driven inflammation at host/environment interfaces, ventilator-induced lung injury, pancreatitis and liver damage. Overall, preclinical studies would support therapeutic administration of seemingly well-tolerated recombinant IL-22 for treatment of an array of acute diseases manifested in epithelial tissues. However, the feasibility of prolonged administration of this cytokine is expected to be restricted by the tumourigenic potential of the IL-22/STAT3 axis. IL-22, moreover, apparently displays an inherent context-specific capacity to amplify distinct aspects of autoimmune inflammation. Here, the prospects, expectations and restrictions of IL-22 administration in tissue-protective therapy are discussed.

Interleukin-25 induces pulmonary arterial remodeling via natural killer T cell-dependent mechanisms

BACKGROUND

Recent studies have shown that prolonged Th2-type immune inflammation in the lung induces pulmonary arterial remodeling, in part through the induction of resistin-like molecule α (RELMα) expression. However, the role of interleukin-25 (IL-25; which promotes this inflammation) in the development of the pulmonary arterial remodeling remains unknown.

METHODS

Ovalbumin (OVA)-sensitized C57BL/6 mice were challenged with OVA inhalation 3 times a week for 3 weeks. The effects of neutralizing anti-IL-25 antibody on OVA-induced pulmonary arterial remodeling and RELMα expression in the lung were examined. The pulmonary arterial remodeling and RELMα expression in the lung were examined in lung-specific IL-25 transgenic mice (CC10 IL-25 mice) and CC10 IL-25 mice in a natural killer T (NKT) cell-deficient background (CC10 IL-25 NKT(-/-) mice).

RESULTS

Repeated OVA inhalation induced pulmonary arterial wall thickening and the expression of IL-25 and RELMα mRNA in the lung in OVA-sensitized mice. Injection of neutralizing anti-IL-25 antibody inhibited OVA-induced pulmonary arterial wall thickening and RELMα expression in the lung. CC10 IL-25 mice, but not CC10 IL-25 NKT(-/-) mice, spontaneously developed pulmonary arterial wall thickening and RELMα expression in the lung at 6 months of age.

CONCLUSIONS

Prolonged expression of IL-25 in the lung induces pulmonary arterial wall thickening by NKT cell-dependent mechanisms.