IL-16 inhibits IL-5 production by antigen-stimulated T cells in atopic subjects

Comparison of Pulmonary Function and Inflammation in Children/Adolescents with New-Onset Asthma with Different Adiposity Statuses

(1) Background: The relationship between obesity and asthma is still uncertain. This study aimed to investigate the effect of overweight/obesity on the pulmonary function of patients with new-onset pediatric asthma and explore the possible causative factors related to concomitant obesity and asthma. (2) Methods: Patients aged 5 to 17 years old with newly diagnosed mild to moderate asthma were recruited from June 2018 to May 2019, from a respiratory clinic in Shanghai, China. Participants were categorized into three groups: normal weight, overweight, and obese asthma. A family history of atopy and patients’ personal allergic diseases were recorded. Pulmonary function, fractional exhaled nitric oxide (FeNO), eosinophils, serum-specific immunoglobulins E (sIgE), serum total IgE (tIgE), and serum inflammatory biomarkers (adiponectin, leptin, Type 1 helper T, and Type 2 helper T cytokines) were tested in all participants. (3) Results: A total of 407 asthma patients (197 normal weight, 92 overweight, and 118 obese) were enrolled. There was a reduction in forced expiratory volume in the first second (FEV1)/forced vital capacity (FVC), FEV1/FVC%, and FEF25–75% in the overweight/obese groups. No difference was found between the study groups in the main allergy characteristics. Leptin levels were higher while adiponectin was lower in asthmatics with obesity. Higher levels of IL-16 were found in overweight/obese asthmatic individuals than in normal-weight individuals. (4) Conclusions: Obesity may have an effect on impaired pulmonary function. While atopic inflammation plays an important role in the onset of asthma, nonatopic inflammation (including leptin and adiponectin) increases the severity of asthma in overweight/obese patients. The significance of different levels of IL-16 between groups needs to be further studied.

Interleukin-16 aggravates ovalbumin-induced allergic inflammation by enhancing Th2 and Th17 cytokine production in a mouse model

Asthma is a chronic inflammatory disease that involves a variety of cytokines and cells. Interleukin-16 (IL-16) is highly expressed during allergic airway inflammation and is involved in its development. However, its specific mechanism of action remains unclear. In the present study, we used an animal model of ovalbumin (OVA)-induced allergic asthma with mice harboring an IL-16 gene deletion to investigate the role of this cytokine in asthma, in addition to its underlying mechanism. Increased IL-16 expression was observed during OVA-induced asthma in C57BL/6J mice. However, when OVA was used to induce asthma in IL-16^-/- mice, a diminished inflammatory reaction, decreased bronchoalveolar lavage fluid (BALF) eosinophil numbers, and the suppression of OVA-specific IgE levels in the serum and BALF were observed. The results also demonstrated decreased levels of T helper type 2 (Th2) and Th17 cytokines upon OVA-induced asthma in IL-16^-/- mice. Hence, we confirmed that IL-16 enhances the lung allergic inflammatory response and suggest a mechanism possibly associated with the up-regulation of IgE and the promotion of Th2 and Th17 cytokine production. This work explored the mechanism underlying the regulation of IL-16 in asthma and provides a new target for the clinical treatment of asthma.

High-Dose Dexamethasone Alters the Increase in Interleukin-16 Level in Adult Immune Thrombocytopenia

Adult primary immune thrombocytopenia (ITP) is an autoimmune-mediated haemorrhagic disorder. Interleukin-16 (IL-16) can directly affect cellular or humoural immunity by mediating the cellular cross-talk among T cells, B cells and dendritic cells. Several studies have focused on IL-16 as an immunomodulatory cytokine that takes part in Th1 polarization in autoimmune diseases. In this study, we investigated IL-16 expression in the bone marrow supernatant and plasma of ITP patients and healthy controls. What's more, we detected IL-16 expression in ITP patients with the single-agent 4-day high-dose dexamethasone (HD-DXM) therapy. In patients with active ITP, bone marrow supernatant and plasma IL-16 levels increased (P < 0.05) compared with those of healthy controls. In the meantime, the mRNA expression in BMMCs (pro-IL-16, caspase-3) and PBMCs (pro-IL-16, caspase-3 and T-bet) of ITP patients was increased (P < 0.05) relative to those of healthy controls. In patients who responded to HD-DXM therapy, both plasma IL-16 levels and gene expression in PBMCs (pro-IL-16, caspase-3, and T-bet) were decreased (P < 0.05). In summary, the abnormal level of IL-16 plays important roles in the pathogenesis of ITP. Regulating Th1 polarization associated with IL-16 by HD-DXM therapy may provide a novel insight for immune modulation in ITP.

IL-16/miR-125a axis controls neutrophil recruitment in pristane-induced lung inflammation

Severe lung inflammation and alveolar hemorrhage can be life-threatening in systemic lupus erythematosus (SLE) patients if not treated early and aggressively. Neutrophil influx is the driver key of this pathology, but little is known regarding the molecular events regulating this recruitment. Here, we uncover a role for IL-16/mir-125a in this pathology and show not only that IL-16 is a target for miR-125a but that reduced miR-125a expression in SLE patients associates with lung involvement. Furthermore, in the pristane model of acute "SLE-like" lung inflammation and alveolar hemorrhage, we observed reduced pulmonary miR-125a and enhanced IL-16 expression. Neutrophil infiltration was markedly reduced in the peritoneal lavage of pristane-treated IL-16-deficient mice and elevated following i.n. delivery of IL-16. Moreover, a miR-125a mimic reduced pristane-induced IL-16 expression and neutrophil recruitment and rescued lung pathology. Mechanistically, IL-16 acts directly on the pulmonary epithelium and markedly enhances neutrophil chemoattractant expression both in vitro and in vivo, while the miR-125a mimic can prevent this. Our results reveal a role for miR-125a/IL-16 in regulating lung inflammation and suggest this axis may be a therapeutic target for management of acute lung injury in SLE.

Neutrophil-Derived Interleukin 16 in Premetastatic Lungs Promotes Breast Tumor Cell Seeding

The premetastatic niche in distant organs prior to metastatic cell arrival emerged as an important step in the metastatic cascade. However, molecular mechanisms underlying this process are still poorly understood. In particular, whether neutrophil recruitment at a premetastatic stage promotes or inhibits metastatic cell seeding has to be clarified. We aimed at unraveling how neutrophil infiltration in lung parenchyma induced by the distant primary tumor influences the establishment of lung metastasis. Elevated neutrophil counts and IL-16 levels were found in premetastatic lungs in a syngenic mouse model using 4T1 tumor cells. 4T1 cell-derived soluble factors stimulated IL-16 secretion by neutrophils. The functional contribution of IL-16 is supported by metastasis burden reduction in lungs observed on instillation of an IL-16 neutralizing antibody. Moreover, IL-16 promotes in vitro 4T1 cell adhesiveness, invasiveness, and migration. In conclusion, at a premetastatic stage, neutrophil-derived IL-16 favors tumor cell engraftment in lung parenchyma.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

IL-16 effects on A549 lung epithelial cells: dependence on CD9 as an IL-16 receptor?

Interleukin-16 (IL-16) is a pro-inflammatory cytokine released by many types of cells found in the lungs, including normal airway and alveolar epithelial cells. Though a chemotactin for CD4(+) cells and eosinophils, IL-16 also modulates their production of factors that influence inflammatory lung diseases, e.g., asthma and allergic rhinitis. To date, little is known about any potential autocrine-like regulatory effects of IL-16. Using a model human alveolar basal epithelial A549 cell line, the present study sought to assess lung epithelial cell responses to IL-16. Potential induced effects on cell growth/function were assessed using MTT reduction, lactate dehydrogenase release, and 5-bromo-2-deoxyuridine incorporation assays. As IL-16 (at locally high levels) can induce CD4(+) cell death via apoptosis, this potential outcome among the A549 cells was also evaluated using TUNEL and changes in expression of caspase-3 and the pro-apoptotic and anti-apoptotic proteins of Bcl-2 family. The data here indicated that IL-16 inhibited A549 cell growth/function and this was associated with a marked increase in apoptosis characterized by DNA fragmentation, activation of caspase-3, and altered pro-apoptotic protein expression. Since lung epithelial cells lack the CD4 that may bind IL-16, it has been suggested that CD9 may act as an alternate receptor for this cytokine (i.e., an IL-16R). Thus, these studies also sought to determine the extent of CD9 expression on A549 cells and if any/all observed IL-16-induced changes were mediated by CD9. Flow cytometric analyses revealed the cells to be CD9(+)CD4(-). However, neutralization of the purported IL-16R with anti-CD9 antibody could not block the cytotoxic/growth inhibiting effects of IL-16. The only exception appeared to be a mitigation of a chemotactic effect of IL-16; however, studies with an equal amount of non-specific antibody (of same isotype as the anti-CD9) revealed this effect to be artefactual. The neutralization study results thus suggest to us that as-yet undefined pathway(s) exist through which IL-16 may act to exert growth inhibiting/apoptosis-inducing effects on A549 cells, a cell line routinely used as a model for lung epithelial cells.

Combined T regulatory cell and Th2 expression profile identifies children with cow's milk allergy

The role of T regulatory cells in spontaneous recovery from cow's milk allergy (CMA) is unclear. We investigated the mRNA expression of 12 T-cell markers and the protein expression of CD4, CD25, CD127, FoxP3 after in vitro beta-lactoglobulin stimulation of peripheral blood mononuclear cells from children with persisting CMA (n=16), early recovery (n=20) or no atopy (n=21). Artificial neural networks with exhaustive search for all marker combinations revealed that markers FoxP3, Nfat-C2, IL-16 and GATA-3 distinguished patients with persisting CMA most accurately from other study groups. FoxP3 mRNA expression following beta-lactoglobulin stimulation was highest in children with persisting CMA. Also the FoxP3 intensity in CD4(+) CD25(high)CD127(low) cells was higher in children with CMA compared with non-atopic children. The expression profile of both Th2- and T regulatory cell-related genes thus reflects the clinical activity of CMA. Tolerance, in contrast, is not characterized by activation of circulating T regulatory cells.

Human mid-gestation amniotic fluid contains interleukin-16 bioactivity

CD4-positive cells are detectable in the human fetal gastrointestinal tract from 11 weeks of gestation. Interleukin-16 (IL-16) is a chemoattractant for CD4(+) cells and, via fetal swallowing of amniotic fluid, could mediate the influx of CD4(+) cells into the fetal gut. We have shown that IL-16 was detectable in human amniotic fluid at 16-18 weeks of gestation (mid-pregnancy) but was not detectable at term (late pregnancy; > 37 weeks of gestation). Similarly, mid-pregnancy, but not late pregnancy, amniotic fluid contained chemotactic activity for CD4(+) T cells, this activity was reduced by 58% in the presence of a neutralizing anti-IL-16 antibody. The levels of IL-16 in fetal plasma at 16-24 weeks of gestation were very high, and decreased significantly by 25-36 weeks but at > 37 weeks remained significantly higher than adult levels. IL-16 transcripts were detectable in whole tissue extracts of fetal gut, skin and placenta but not in amniocytes, and IL-16 immunoreactivity was detectable in cells within the lamina propria of the fetal gut and within the skin, where it was associated with the basement membrane. Neither IL-16 levels nor chemotactic activity for CD4(+) T cells in mid-pregnancy amniotic fluid was related to atopic outcomes at 1 year of age. IL-16 might have an important role in the early development of the human immune system and/or in regulating fetal and maternal immunological responsiveness during pregnancy.

Preferential migration of T regulatory cells induced by IL-16

As a natural ligand for CD4, IL-16 has been shown to preferentially induce migration in Th1 cells, and, in long-term cultures with IL-2, IL-16 facilitates the expansion of CD4(+)CD25(+) cells. In addition, IL-16 has an immunomodulatory role in asthmatic inflammation, as exogenous administration significantly reduces inflammation and airway hyperreactivity. The mechanism for this, however, is not clear. Based on its functional characteristics and potential immunomodulatory role, we investigated the ability of IL-16 to recruit and influence the development of T regulatory (Treg) cells. We now demonstrate that IL-16 preferentially induces migration in a CD25(+)CTLA-4(+) human T cell subset and that responding cells produce IFNgamma and TGFbeta but not IL-10. These cells are relatively unresponsive to antigenic stimulation and can suppress proliferation and IL-5, but not IFNgamma, production by autologous T cells. We further demonstrate that IL-16-recruited cells are enriched for Forkhead box P3 (Foxp3). In addition, we find that IL-16 stimulation may facilitate de novo induction of Foxp3(+) Treg cells, because the stimulation of FoxP3-negative T cells for 48 h results in the expression of FoxP3 mRNA and protein. These data indicate that at sites of inflammation IL-16 may contribute to selective Treg cell expansion through the preferential induction of a migratory response from existing Treg cells, as well as by the induction of de novo generation of FoxP3(+) cells. These findings offer a potential mechanism for the immunosuppressive effects of IL-16 seen in Th2-mediated inflammation.

Elevated serum levels of interleukin-15 and interleukin-16 in preeclampsia

A generalized inflammatory response has been considered to be the main pathology and has an important role in the pathogenesis of preeclampsia. The immune aberrations per se and immunomodulatory milieu present in serum need to be elucidated. The purpose of the current investigation was to characterize changes in serum levels of interleukin (IL)-15 and IL-16 in preeclampsia. Thirty-seven women with preeclampsia were recruited and 36 age- and gestational age-matched women with normal pregnancy served as control. Levels of IL-15 and IL-16 were detected with immune assays in all serum samples. We found that serum levels of IL-15 and IL-16 were significantly higher in preeclampsia than in normal pregnancy (p<0.001 for both). There were significant differences in serum IL-15 and IL-16 between mild and severe preeclampsia (p<0.01 for both). Our data corroborate the hypothesis of an increased inflammatory response in preeclampsia, as illustrated by the elevated serum levels of IL-15 and IL-16, suggesting their possible role in the pathogenesis of preeclampsia. These associations may offer insight into the pathophysiology of preeclampsia.

Interleukin-16 Inhibits Immunoglobulin E Production by B Lymphocytes

BACKGROUND

The increased production of IgE is a hallmark of atopic disorders. CD4+ T cells regulate the production of Immunoglobulin (Ig) E by B cells. Interleukin (IL) 16, a CD4+ specific cytokine, is highly expressed at sites of allergic inflammation. Our aim was to determine the effect of IL-16 on IgE production in atopic subjects.

METHODS

Freshly isolated peripheral blood mononuclear cells (PBMC) from atopic subjects were stimulated with recombinant IL (rIL) 4 and anti-CD40 antibody to promote IgE production in the presence or absence of rIL-16 added at different time intervals prior to stimulation. The levels of IgE in cell culture supernatants collected at day 14 were measured by ELISA. The effect of IL-16 on the expression of the Cepsilon transcript was evaluated by reverse-transcription polymerase chain reaction. To evaluate whether the modulatory effect of IL-16 on IgE production was mediated by interferon-gamma (IFN-gamma), anti-CD40/IL-4-stimulated PBMC were cultured in the presence of rIL-16 and neutralizing concentrations of anti-IFN-gamma antibody.

RESULTS

PBMC stimulated with rIL-4 (400 U/ml) and anti-CD40 monoclonal antibody (0.5 microg/ml) produced significant amounts of IgE (range: 1.3-46.0 ng/ml). The addition of rIL-16 twenty-four hours before stimulation significantly reduced the levels of IgE released by anti-CD40/IL-4-stimulated PBMC (0.5-29.6 ng/ml, p < 0.05). IL-16 reduced the expression of the Cepsilon transcript in stimulated PBMC. IL-16 induced the expression of IFN-gamma mRNA. However, the use of anti-IFN-gamma antibody did not alter the effect of IL-16 on IgE production. Rescue doses of IL-13 did not restore the production of IgE by PBMC treated with IL-16. IL-16 did not alter IgE production in CD14-depleted cell preparations suggesting that the IL-16-mediated effects on IgE production may be related to CD14+ cells.

CONCLUSION

These data show that IL-16 inhibits IgE production and therefore may play an important regulatory role in atopic disorders.

Not-so-sweet sixteen: the role of IL-16 in infectious and immune-mediated inflammatory diseases

Over the past two decades, our understanding of interleukin-16 (IL-16) has increased substantially. Initial studies characterizing IL-16 as a chemotactic cytokine (but not a chemokine) just scratched the surface of the unique properties of this cytokine. Since then, scientists have determined that IL-16 has a wide range of effects on cells, including upregulation of CD25, induction of cells to progress to the G(1) phase, inhibition of antigen- specific proliferation yet with retained antigen nonspecific proliferative properties, and discovery of a novel neuronal form with unique properties. Recently, a plethora of studies have implicated IL-16 in exacerbation of infectious, immune-mediated, and autoimmune inflammatory disorders, including atopic dermatitis, irritable bowel syndrome, systemic lupus erythematosus, neurodegenerative disorders, and viral infections. Herein, we review the body of evidence supporting a role for IL-16 in infectious and immune-mediated inflammatory disorders and explore the known and possible mechanism of actions in the numerous diseases.

Interleukin-16 inhibits interleukin-13 production by allergen-stimulated blood mononuclear cells

Expression of interleukin (IL)-16 is increased in bronchial mucosal biopsies of atopic asthmatics compared to normal controls. The functional significance of increased expression of IL-16 at sites of allergic inflammation is not yet clear. We have previously shown that IL-16 inhibits IL-5 secretion by allergen-stimulated peripheral blood mononuclear cells (PBMC). We investigated whether IL-16 inhibits the production of other T helper 2 cytokines, namely IL-13 and IL-4, by allergen-specific T cells. PBMC from ragweed-sensitive atopic subjects were stimulated with allergen extract for cytokine production in the presence or absence of rhIL-16. Production of cytokines was assessed by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction. To evaluate whether the modulatory effect of IL-16 on cytokine synthesis was mediated by interferon-gamma (IFN-gamma), IL-10, IL-12 or IL-18, allergen-stimulated PBMC were cultured in presence of IL-16 and neutralizing concentrations of relevant antibodies. Allergen-stimulated PBMC produced significantly elevated levels of IL-13 (90-740 pg/ml) as compared to unstimulated PBMC (0-375 pg/ml, P < 0.01). Addition of rhIL-16 resulted in down-regulation of IL-13 mRNA expression as well as significantly reduced amounts of IL-13 released by allergen-stimulated PBMC (0-457 pg/ml, P < 0.001), as observed for IL-5. No effect of IL-16 was observed on IL-4 mRNA expression. Treatment with IL-16 resulted in increased levels of IL-10 and IL-18 in allergen-stimulated cell culture. Neutralization of IFN-gamma, IL-12, IL-10 or IL-18 did not alter the inhibitory effects of IL-16 on IL-13 and IL-5 secretion by allergen-stimulated PBMC. IL-16 did not modify IL-13 synthesis by anti-CD3-stimulated CD4(+) T cells, but it significantly reduced the production of IL-5. These data suggest that IL-16 may play an important immunoregulatory role in allergic states in response to allergen.

Expression of interleukin-16 in allergic rhinitis

BACKGROUND

Interleukin-16 (IL-16) has been characterized as a chemoattractant for a variety of CD4+ T cells. Several inflammatory diseases, including allergic disorders, have been reported to correlate with IL-16. We first examined the IL-16 expression of serum and mucosal tissue in patients with allergic rhinitis.

METHODS

Forty-eight patients with a clinical history of house dust mite (HDM) or pollen-sensitive allergic rhinitis were included in this study. Serum IL-16 was analyzed by enzyme-linked immunosorbent assay (ELISA). IL-16 expression of nasal mucosa was detected by immunohistochemistry.

RESULTS

IL-16 levels were elevated in the serum of patients with allergic rhinitis compared with normal controls. In particular, serum IL-16 levels in HDM-sensitive patients were higher than those in pollen-sensitive patients. IL-16 was significantly correlated with eosinophils in the peripheral blood of allergic rhinitis patients. Histologically, IL-16 was expressed in infiltrated lymphocytes and nasal gland cells.

CONCLUSIONS

Our data indicate that one of the sources of elevated serum IL-16 in allergic patients may be gland cells and lymphocytes in allergic nasal mucosa. This IL-16 cytokine may be strongly associated with the developmental mechanism of allergic rhinitis.

Interleukin-16 and peptide derivatives as immunomodulatory therapy in allergic lung disease

The therapeutic potential of interleukin (IL)-16 and derived peptides in allergic asthma is considered, focusing on key interactions with CD4 and associated chemokine receptors. IL-16 is a pleiotropic cytokine that has multiple effector functions with putative roles in varied T cell-mediated inflammatory diseases, such as asthma, inflammatory bowel disease and atopic dermatitis. Both in vitro and in vivo, IL-16 downregulates antigen-driven T cell activation, T helper 2 cytokine production and allergic airway inflammation. Peptides derived from the C-terminal bioactive portion of IL-16 offer advantages related to their retained immunomodulatory properties and absence of signalling in and chemoattraction to T cells.

Immunomodulatory cytokines in asthmatic inflammation

The development of asthmatic inflammation involves a complex array of cytokines that promote the recruitment and activation of a number of different immune cells. While factors involved in initiating and establishing inflammation are well characterized, the process by which this pro-inflammatory cascade is regulated is less well understood. The identification and characterization of immunomodulatory cytokines in asthma has been a difficult proposition. Many of the putative regulatory factors have pleiotropic bioactivities and have been characterized as pro-inflammatory in association with certain pathologic conditions. This chapter addresses the potential role of several endogenous factors which appear to attenuate asthmatic inflammation. Understanding the integration of these factors into the regulation of the inflammatory process will likely result in novel therapeutic approaches.

Sustained linked stimulation via CD3 and CD4 is required for the IL-4-independent development of IL-4 synthesizing CD4+ T cells

Previous work has shown that CD4 engagement can promote the development of interleukin-4-producing cells from naive CD4+ T cells activated with anti-CD3 antibody and interleukin-2 in the absence of other exogenous signals, including interleukin-4 itself. When CD44low CD4+ T cells were activated with immobilized anti-CD3 antibody and interleukin-2, they proliferated and produced interferon-gamma but not interleukin-4. Co-immobilization of antibodies to CD3 and CD4 enhanced cell recoveries and induced interleukin-4 as well as interferon-gamma synthesis. Here we show that these effects of CD4 ligation were not observed when anti-CD4 antibody was replaced with another CD4 ligand, interleukin-16, or when the anti-CD3 and anti-CD4 antibodies were spatially separated by immobilization on different beads. Removal of the anti-CD4 antibodies within the first three days of stimulation also prevented the development of detectable interleukin-4-producing cells. The data suggest that interleukin-4-independent priming of interleukin-4-producing cells in this system requires sustained stimulation via both the T cell receptor and CD4 with close physical association between the ligands for these two receptors.

IL-16 in the airways of lung allograft recipients with acute rejection or obliterative bronchiolitis

Acute rejection (AR) is the principal risk factor for obliterative bronchiolitis (OB), the major complication of lung transplantation. It is known that activated CD4+ T lymphocytes are involved in the development of AR and that interleukin (IL)-16 can inhibit the activity of CD4+ T lymphocytes. In this study, we evaluated whether the concentration of IL-16 in the airways is altered in AR or OB and, if so, how this IL-16 concentration relates to the number or activity of airway lymphocytes. The concentration of IL-16 protein was measured in bronchoalveolar lavage (BAL) fluid at three time-points in lung allograft recipients with either AR or OB and in matched controls using ELISA. The concentration of soluble IL-2 receptor (R) protein was measured in BAL fluid using ELISA as well, as an indicator of lymphocyte activity. The percentage of airway lymphocytes was evaluated by performing BAL differential cell counts. Lung allograft recipients with AR displayed lower IL-16 concentrations compared with matched control patients and this IL-16 concentration correlated negatively with the sIL-2R concentration, but it did not correlate with the percentage of lymphocytes in BAL fluid. In contrast, in BAL fluid from lung allograft recipients with OB, the IL-16 concentration was not altered compared with matched control patients and it did not correlate with the percentage of lymphocytes or with the sIL-2R concentration. These data are compatible with an increase in IL-16 playing a protective role against AR but not against OB and, hypothetically, this type of protective effect could be exerted via a down-regulation of the activity of T lymphocytes.

Exogenous interleukin-16 inhibits antigen-induced airway hyper-reactivity, eosinophilia and Th2-type cytokine production in mice

BACKGROUND

IL-16 has been described as a natural soluble CD4-ligand with immunosuppressive effects in vitro. However, little is known about the effect of IL-16 on immune responses in vivo.

OBJECTIVE

In the present study, we examined the effect of IL-16 administration in a murine model of allergic asthma. Next, we determined whether these effects were mediated by modulation of CD4+ T lymphocytes.

METHODS AND RESULTS

Intraperitoneal administration of IL-16 completely inhibits antigen-induced airway hyper-responsiveness and largely decreases the number of eosinophils in bronchoalveolar lavage fluid (> 90%) and airway tissue of ovalbumin-sensitized and challenged mice. Firstly, it appears that thoracic lymph node cells isolated from in vivo IL-16-treated ovalbumin-challenged animals produce less IL-4 (77%) and IL-5 (85%) upon antigenic re-stimulation, when compared to vehicle-treated mice. Secondly, pre-incubation of lymphocytes with IL-16 in vitro reduces antigen-induced proliferation (55%) and Th2-type cytokine production (IL-4; 56%, IL-5; 77%). Thirdly, the presence of IL-16 during priming cultures of TCR transgenic T cells (DO11.10), reduces IL-4 (33%) and IL-5 (35%), but not IL-10 and IFNgamma levels upon re-stimulation.

CONCLUSION

It can be concluded that IL-16 has potent immunosuppressive effects on a Th2dominated allergic airway response.

IL-16 promotes leukotriene C(4) and IL-4 release from human eosinophils via CD4- and autocrine CCR3-chemokine-mediated signaling

Human eosinophils are potential sources of inflammatory and immunomodulatory mediators, including cysteinyl leukotrienes, chemokines, and cytokines, which are pertinent to allergic inflammation. We evaluated the means by which IL-16, a recognized eosinophil chemoattractant, might act on eosinophils to affect their capacity to release leukotriene C(4) (LTC(4)) or their preformed stores of chemokines (eotaxin, RANTES) or Th1 (IL-12) or Th2 (IL-4) cytokines. IL-16 dose dependently (0.01-100 nM) elicited new lipid body formation, intracellular LTC(4) formation at lipid bodies, and priming for enhanced calcium ionophore-activated LTC(4) release. IL-16 also elicited brefeldin A-inhibitable, vesicular transport-mediated release of preformed IL-4, but not IL-12, from eosinophils. CD4 is a recognized IL-16R, and accordingly anti-CD4 Fab, soluble CD4, and a CD4 domain 4-based IL-16 blocking peptide inhibited the actions of IL-16 on eosinophils. Although CD4 is not G-protein coupled, pertussis toxin inhibited IL-16-induced eosinophil activation. IL-16 actions were found to be mediated by the autocrine activity, not of platelet-activating factor, but rather of endogenous CCR3-acting chemokines. IL-16 induced the rapid vesicular transport-mediated release of RANTES. The effects of IL-16 were blocked by CCR3 inhibitors (met-RANTES, anti-CCR3 mAb) and by neutralizing anti-eotaxin and anti-RANTES mAbs, but not by platelet-activating factor receptor antagonists (CV6209, BN52021). RANTES and eotaxin each enhanced LTC(4) and IL-4 (but not IL-12) release. Therefore, IL-16 activation of eosinophils is CD4-mediated to elicit the extracellular release of preformed RANTES and eotaxin, which then in an autocrine fashion act on plasma membrane CCR3 receptors to stimulate both enhanced LTC(4) production and the preferential release of IL-4, but not IL-12, from within eosinophils.

Il-9 stimulates release of chemotactic factors from human bronchial epithelial cells

Interleukin (IL)-9 is a T helper 2 cytokine implicated as a candidate gene and contributor to human asthma. We hypothesized that the inflammatory potential of bronchial epithelium is affected by its local environment and explored this hypothesis with respect to the effect of IL-9 on bronchial epithelium. We investigated the response of primary and immortalized human bronchial epithelial cells to IL-9 stimulation with respect to the release of T-cell chemoattractant factors. In response to IL-9, the HBE4-E6/E7 cell line, but not BEAS-2B cells, released the T-cell chemoattractants IL-16 and regulated on activation, normal T cells expressed and secreted (RANTES) in a dose-dependent fashion. We found a similar dose response to IL-9 in primary cells from bronchial brushings of healthy subjects and that nearly all of the T-cell chemoattraction was attributable to IL-16 and RANTES. Reverse transcriptase/polymerase chain reaction of BEAS-2B, HBE4-E6/E7, and primary cells from two subjects revealed messenger RNA for IL-9 receptor (IL-9R) alpha but not in BEAS-2B cells. Fluorescence-activated cell sorter analysis of HBE4-E6/E7 and primary cells confirmed surface expression of the IL-9 receptor. Costimulation of both cell types with IL-9 and antibody to either gamma-common chain or IL-9Ralpha completely blocked the release of T-cell chemoattractant activity, confirming the primary role of a functioning IL-9 receptor for IL-9 signaling in HBE4-E6/E7 and primary bronchial epithelial cells. We conclude that IL-9 is a stimulus for airway epithelial cell release of T-cell chemoattractant factors, which in turn may modulate the immune response in allergic airway inflammation.