Differential regulation of allergen-specific T(H2)- but not T(H1)-type responses by alveolar macrophages in atopic asthma

Role of Metabolic Reprogramming in Pulmonary Innate Immunity and Its Impact on Lung Diseases

Lung innate immunity is the first line of defence against inhaled allergens, pathogens and environmental pollutants. Cellular metabolism plays a key role in innate immunity. Catabolic pathways, including glycolysis and fatty acid oxidation (FAO), are interconnected with biosynthetic and redox pathways. Innate immune cell activation and differentiation trigger extensive metabolic changes that are required to support their function. Pro-inflammatory polarisation of macrophages and activation of dendritic cells, mast cells and neutrophils are associated with increased glycolysis and a shift towards the pentose phosphate pathway and fatty acid synthesis. These changes provide the macromolecules required for proliferation and inflammatory mediator production and reactive oxygen species for anti-microbial effects. Conversely, anti-inflammatory macrophages use primarily FAO and oxidative phosphorylation to ensure efficient energy production and redox balance required for prolonged survival. Deregulation of metabolic reprogramming in lung diseases, such as asthma and chronic obstructive pulmonary disease, may contribute to impaired innate immune cell function. Understanding how innate immune cell metabolism is altered in lung disease may lead to identification of new therapeutic targets. This is important as drugs targeting a number of metabolic pathways are already in clinical development for the treatment of other diseases such as cancer.

Innate immunity as the orchestrator of allergic airway inflammation and resolution in asthma

The respiratory system is constantly in direct contact with the environment and, has therefore, developed strong innate and adaptive immune responses to combat pathogens. Unlike adaptive immunity which is mounted later in the course of the immune response and is naive at the outset, innate immunity provides the first line of defense against microbial agents, while also promoting resolution of inflammation. In the airways, innate immune effector cells mainly consist of eosinophils, neutrophils, mast cells, basophils, macrophages/monocytes, dendritic cells and innate lymphoid cells, which attack pathogens directly or indirectly through the release of inflammatory cytokines and antimicrobial peptides, and coordinate T and B cell-mediated adaptive immunity. Airway epithelial cells are also critically involved in shaping both the innate and adaptive arms of the immune response. Chronic allergic airway inflammation and linked asthmatic disease is often considered a result of aberrant activation of type 2 T helper cells (Th2) towards innocuous environmental allergens; however, innate immune cells are increasingly recognized as key players responsible for the initiation and the perpetuation of allergic responses. Moreover, innate cells participate in immune response regulation through the release of anti-inflammatory mediators, and guide tissue repair and the maintenance of airway homeostasis. The scope of this review is to outline existing knowledge on innate immune responses involved in allergic airway inflammation, highlight current gaps in our understanding of the underlying molecular and cellular mechanisms and discuss the potential use of innate effector cells in new therapeutic avenues.

Local and systemic immunological parameters associated with remission of asthma symptoms in children

The immunological and clinical parameters that are associated with asthma remission are poorly understood. The cytokine and local mediator changes associated with the resolution of asthma symptoms were examined in three groups of subjects 12-18 years of age (n = 15 in each group): (a) continuing asthma group (CA) who had persistent symptoms since early childhood, (b) an age, sex and atopic status-matched group who had persistent symptoms in early childhood but in whom these had resolved (RA), and (c) a non-atopic, non-asthmatic control group. Clinical parameters, sputum cell counts, peripheral blood mononuclear cell (PBMC) cytokine production and activation marker expression were determined. All of the CA had methacholine airway hyperresponsiveness compared with only half of the RA subjects. The CA showed elevated numbers of eosinophils and increased ECP and IL-5 in sputum, which were not observed in the RA. PBMC cytokine studies revealed increased production of the type 1 cytokines IL-12, IFN-γ and TNF-α in the CA group compared with the RA group, under a range of activation conditions, however, the production of IL-4 and IL-5 were unchanged. These findings suggest that decreased type 1 cytokine expression as well as decreased eosinophilic inflammation is associated with the resolution of asthma symptoms.

Alveolar macrophages modulate allergic inflammation in a murine model of asthma

The role of alveolar macrophages (AMs) in the pathogenesis of asthma is still unknown. The aim of the present study was to investigate the effects of AM in the murine model of asthma. AMs were selectively depleted by liposomes containing clodronate just before allergen challenges, and changes in inflammatory cells and cytokine concentrations in bronchoalveolar lavage (BAL) fluid were measured. AMs were then adoptively transferred to AM-depleted sensitized mice and changes were measured. Phenotypic changes in AMs were evaluated after in vitro allergen stimulation. AM-depletion after sensitization significantly increased the number of eosinophils and lymphocytes and the concentrations of IL-4, IL-5 and GM-CSF in BAL fluid. These changes were significantly ameliorated only by adoptive transfer of unsensitized AMs, not by sensitized AMs. In addition, in vitro allergen stimulation of AMs resulted in their gaining the ability to produce inflammatory cytokines, such as IL-1β, IL-6 and TNF-α, and losing the ability to suppress GM-CSF concentrations in BAL fluid. These findings suggested that AMs worked probably through GM-CSF-dependent mechanisms, although further confirmatory experiments are needed. Our results indicate that the role of AMs in the context of airway inflammation should be re-examined.

TH1/TH2 balance in concomitant immediate and delayed-type hypersensitivity diseases

In spite of the observation of mutual inhibitory properties of TH1 and TH2 CD4+ cells, a group of patients developed simultaneously immediate and delayed-type hypersensitivity reactions that are theoretically antagonistic. Patients presenting concomitant hypersensitivity reactions were evaluated for cytokine production. PBMC from 45 patients and 13 non-atopic individuals were cultured with mite allergen and mitogen and the supernatants obtained were evaluated for cytokine production by ELISA. The analysis of the cytokines levels revealed increased production of pro-inflammatory cytokine TNF-alpha in the non-atopic individuals after specific and mitogen stimulus. The IL-4 was largely observed on serum samples and IL-5 levels were higher in the double sensitized group (group DerpNi) after PHA stimulus. The IL-13 levels were increased in sensitized groups (Derp and DerpNi groups) after PHA stimuli. Atopic patients (Derp and DerpNi groups) presented lowest levels IFN-gamma and the analysis of TGF-beta production after rDER P I stimulation have shown increased levels among sensitized patients to Dermatophagoides pteronyssinus mite. IL-10 levels did not differ after antigen stimulation but basal production was higher on Derp and DerpNi groups. Furthermore, negative correlations were observed between IFN-gamma levels and IL-4, IL-13 and IL-10. This study has shown patients able to react, concomitantly, to the two types of antigens - rDER P I and NiSO4, present distinct pattern of cytokine production. The increased levels of IL-13 in the sensitive individuals to mite antigen (rDER P I) and IFN-gamma in NiSO4 sensitized individuals confirm the role of the type TH2 response in the atopies and TH1 type in DCA.

Alveolar macrophages from allergic lungs are not committed to a pro-allergic response and can reduce airway hyperresponsiveness following ex vivo culture

BACKGROUND

We already demonstrated that adoptive transfer of alveolar macrophages (AMs) from non-allergic rats into AM-depleted allergic rats prevents airway hyperresponsiveness (AHR). We also showed that AMs from non-sensitized, but not from sensitized, allergy-prone rats can prevent AHR following allergen challenge in sensitized allergic animals, establishing the importance of rat immunological status on the modulation of AM functions and suggesting that an allergic lung environment alters AM functions.

OBJECTIVE

We investigated how the activation of allergic AMs can be modulated to reinstitute them with their capacity to reduce AHR.

METHODS

AMs from sensitized Brown Norway rats were cultured ex vivo for up to 18 h in culture media to deprogram them from the influence of the allergic lung before being reintroduced into the lung of AM-depleted sensitized recipient. AHR and cytokines in bronchoalveolar lavage (BAL) were measured following allergen challenge. AMs stimulated ex vivo with Bacillus Calmette-Guerin (BCG) were used as positive controls as BCG induces a T-helper type 1 activation in AMs.

RESULTS

AMs ex vivo cultured for 4-18 h reduced AHR to normal level. Interestingly, pro-allergic functions of AMs were dampened by 18 h culture and they reduced AHR even after spending 48 h in an allergic lung microenvironment. Furthermore, transfer of cultured AMs caused an increase in the levels of IFN-gamma and IL-12 in BAL when compared with their ovalbumin control. After 18 h of ex vivo culture, AMs expressed reduced levels of TNF, IL-1alpha, IL-6, and Arginase-2 mRNAs compared with freshly isolated AMs, suggesting that ex vivo culture exempted AMs from lung stimuli that affected their functions.

CONCLUSIONS

There is a significant crosstalk between lung microenvironment and AMs, affecting their functions. It is also the first report showing that sensitized AMs can be modulated ex vivo to reduce lung pro-allergic environment, opening the way to therapies targetting AMs.

Allergen-induced CD11b+ CD11c(int) CCR3+ macrophages in the lung promote eosinophilic airway inflammation in a mouse asthma model

Although the recruitment of macrophages to the lung is a central feature of airway inflammation, its function in ongoing T(h)2 cell-mediated eosinophilic airway inflammation remains controversial. Here, we have demonstrated that the allergen-induced CD11b(+) CD11c(int) macrophage expressing CC chemokine receptor 3 (CCR3) in the lung performs a crucial function in the induction of eosinophilic asthma in a murine model. In the lungs of normal mice, residential cells evidencing high granularity phenotypically evidenced CD11b(int) CD11c(+) or CD11b(+) CD11c(int) cells, appearing at a 2:1 ratio. After allergen challenge, however, this reverses dramatically, up to a ratio of one to six. Approximately 91% of increased CD11b(+) CD11c(int) cells evidenced the expression of the CCR3 eotaxin receptor, but not other chemokine receptors, such as CCR5 and CXCR4. Interestingly, the CD11b(+) CD11c(int) cells purified from the lungs of OVA (ovalbumin)-sensitized and challenged mice evidenced higher antigen-presenting activity than was observed in CD11b(int) CD11c(+) cells. In order to investigate the in vivo function of CD11b(+) CD11c(int) cells, the cells were isolated from the lungs of OVA-sensitized and challenged mice and then adoptively transferred prior to the allergen challenge of normal mice. In the CD11b(+) CD11c(int)-transferred mice airway hyperresponsiveness, eosinophilic inflammation in the lung and T(h)2 cytokine secretion in the bronchoalveolar lavage fluids were significantly enhanced as the result of OVA challenge, as compared with the mice that received OVA-primed CD90(+) T cells or CD11b(int) CD11c(+) cells. These findings show that CD11b(+) CD11c(int) macrophages expressing CCR3 as key pro-inflammatory cells are both necessary and sufficient for allergen-specific T cell stimulation during ongoing eosinophilic airway inflammation.

Differential expression of monocyte CD163 in single- and dual-asthmatic responders during allergen-induced bronchoconstriction

BACKGROUND

Mononuclear phagocytes play an important role in modulating inflammatory reactions in response to antigen challenge.

OBJECTIVE

To investigate the regulation of CD163, a marker of anti-inflammatory macrophages, during Dermatophagoides pteronyssinus (Dp)-induced bronchoconstriction.

METHODS

Among 110 Dp-sensitive patients who underwent bronchial challenge with Dp, there were 51 dual responders (DR), 32 single responders (SR) and 27 non-responders (NR). Monocyte expression of CD14 and CD163 was evaluated by flow cytometry. Exhaled NO (eNO) concentration was determined on-line using a chemiluminescence analyser. In 21 DR, nine SR and 13 NR-soluble CD163 in plasma was measured by ELISA before, 1, 8 and 24 h after the challenge.

RESULTS

In DR, the baseline expression of monocyte CD163 and eNO were significantly greater than in SR and NR. A pattern of (1) decreased monocyte CD163 expression, (2) unchanged sCD163 and (3) increased eNO in DR was contrasted by a pattern of (1) increased CD163 expression, (2) increased sCD163 and (3) unchanged eNO in SR. During allergen challenge, the changes in monocyte CD163 expression and sCD163 inversely correlated with the changes in eNO.

CONCLUSION

Both pro-inflammatory and anti-inflammatory responses to allergen challenge are uniquely expressed among SR and DR.

Maternal influence in the transmission of asthma susceptibility

Asthma is one of the most common chronic diseases in children, with increasing morbidity and mortality. A genetic predisposition and exposure to allergens have been implicated as major risk factors for the development of asthma. However, increasing evidence indicates that the mother plays a crucial role in mediating the development of fetal-infant immune responses to inhaled allergens. The exact nature and mechanism of this maternal influence and how it might be associated with the development of allergic sensitization and asthma are not clear. Under normal conditions, the maternal environment during pregnancy promotes an initial Th2 skewed immune response in the offspring which transitions to a nonallergic Th1 type response after birth. However, the allergic mother's influence may delay the normal transition to a nonallergic immune response to inhaled allergens in her children, thus increasing the risk for the development of allergic sensitization and/or asthma. Understanding the underlying mechanisms by which the maternal immune environment can influence the development of the fetal-infant immune response to inhaled allergens may lead to identifying new targets for the prevention of allergic sensitization and asthma.

Alleviation of seasonal allergic symptoms with superfine beta-1,3-glucan: a randomized study

BACKGROUND

The incidence of allergic symptoms to cedar pollen has reached epidemic proportions in Japan. Intravenous injection of beta-1,3-glucan in human subjects is known to induce a T(H)1 response, whereas oral uptake does not.

OBJECTIVE

It was examined whether orally ingested, superfine dispersed beta-1,3-glucan (SDG), easily absorbed by intestinal mucosa, would alleviate allergic symptoms.

METHODS

Allergic patients were orally administrated either SDG (n = 30) or nondispersed beta-1,3-glucan (n = 30), and allergic symptoms were assessed clinically in a double-blind, placebo-controlled randomized study.

RESULTS

SDG alleviated ongoing symptoms of Japanese cedar pollen-induced rhinorrhea, sneezing, nasal congestion, and itchy watery eyes, and its oral uptake before symptom onset exhibited preventive effects. Alleviation of allergic symptoms was evident not only for seasonal allergy to cedar pollen but also for perennial allergy. Oral ingestion of beta-1,3-glucan in individuals with allergic tropism could reduce the spontaneous increase in both allergen-specific and total IgE titers. The clinical responses to treatment were well correlated with the capacity of monocytes to bind to beta-1,3-glucan. Although SDG reduced allergic symptoms, the oral uptake of nondispersed beta-1,3-glucan produced no clinical effects, despite the identical amount of beta-1,3-glucan in both preparations.

CONCLUSION

We postulate that orally taken beta-1,3-glucan prepared in a form easily absorbed by intestinal mucosa is able to alleviate cedar pollen-induced allergic symptoms.

CLINICAL IMPLICATIONS

Orally effective SDG might greatly contribute to the resolution of epidemic medical problems of seasonal cedar pollen-induced allergy.

Phenotypic analysis of alveolar macrophages and lymphocytes following allergen inhalation by atopic subjects with mild asthma

BACKGROUND

The airway inflammation associated with allergic asthma is initiated through a complex interaction of antigen-presenting cells (APC) and T lymphocytes resulting in the release of a cascade of cytokines regulating the progress of the allergic inflammatory response. In the present study the state of alveolar macrophage (AM) and T cell activation was investigated following induction of allergic airway inflammation in individuals with atopic asthma.

METHODS

Eleven individuals with mild, atopic asthma received cumulated allergen inhalations. Before and one day after challenge, bronchoalveolar lavage (BAL) was performed, and peripheral blood samples obtained. Ten healthy individuals served as controls. The expression of cell surface markers by BAL fluid AMs and T cells, and by blood T cells, was investigated by flow cytometry.

RESULTS

All patients developed early asthmatic reactions (EAR) with increased numbers of eosinophils and mast cells in BAL fluid following allergen challenge. After allergen challenge, patients had relatively fewer pulmonary CD4+ T cells expressing CD69 and HLA class II and also relatively fewer pulmonary CD8+ T cells expressing HLA class II, compared to before challenge. An increased quantitative expression of CD14 and CD86 was seen within the AM population following allergen challenge.

CONCLUSION

The results indicate a recruitment of non-activated, immature macrophages and CD4+ T cells to the airways as well as an altered phenotype pattern within the AM population following induction of allergic airway inflammation by allergen inhalation challenge in asthma.

Inhibition of human interleukin-13-induced respiratory and oesophageal inflammation by anti-human-interleukin-13 antibody (CAT-354)

BACKGROUND

Allergic asthma is a complex disorder characterized by local and systemic T helper type 2 -cell responses such as the production of IL-13, a cytokine associated with the induction of airway hyper-responsiveness (AHR), chronic pulmonary eosinophilia, airway mucus overproduction and eosinophilic oesophagitis.

OBJECTIVE

Our study aimed to address the therapeutic potential of a human anti-human IL-13 IgG4 monoclonal antibody (CAT-354) in a murine model of respiratory and oesophageal inflammation induced by intratracheal human IL-13.

METHODS

BALB/c mice were treated on days 1 and 3 with CAT-354 (intraperitoneal injection), and human IL-13 was injected intratracheally on days 2 and 4. AHR to methacholine, airway eosinophilia in bronchoalveolar lavage fluid, histologic analysis of goblet cell metaplasia and oesophageal eosinophilia were evaluated.

RESULTS

Human IL-13 induced airway eosinophilia and goblet cell metaplasia in mice in a dose-dependent manner. Moreover, intratracheal dosing with 25 microg of human IL-13 was sufficient to induce AHR, goblet cell metaplasia and oesophageal eosinophilia. Pretreatment with CAT-354 significantly reduced AHR, airway eosinophilia and oesophageal eosinophilia.

CONCLUSION

These results demonstrate that anti-human IL-13 (CAT-354) is a potential therapeutic treatment for allergic airway and oesophageal diseases.

Maternal asthma as a model for examining fetal sex-specific effects on maternal physiology and placental mechanisms that regulate human fetal growth

Studying the effect of maternal asthma during pregnancy on placental function and fetal development has highlighted that there is a strong interaction between mother, placenta and fetus and these interactions appear to be sex-specific. This work has found that the female fetus alters maternal asthma during pregnancy by upregulating maternal inflammatory pathways. When asthma-associated inflammatory pathways are not treated with inhaled steroids during pregnancy, the female fetus has reduced growth and adrenal function due to alterations in placental glucocorticoid metabolism. When the mother uses inhaled steroid for the treatment of her asthma during pregnancy, female fetal growth and placental function are comparable to the control population. The growth of the male fetus appears to be unaffected by asthma or inhaled steroid use. These findings indicate there may be different mechanisms regulating placental glucocorticoid and immune mechanisms depending on fetal sex in both asthmatic and non-asthmatic pregnancies.

DNA vaccines: influenza virus challenge of a Th2/Tc2 immune response results in a Th2/Tc1 response in the lung

For this study, we used DNA-based immunizations to elicit gamma interferon-producing (Tc1) or interleukin 4 (IL-4)-producing (Tc2) CD8 T cells to the influenza virus nucleoprotein. We examined the response of these cells to an intranasal viral challenge. Both the Tc2- and Tc1-biased responses were present in mice with predominantly IL-4-producing (Th2) CD4 T cells. After viral challenge, Tc1 cells underwent more efficient expansion than did Tc2 cells, and only Tc1 cells were detected at the site of infection. In contrast, the CD4 response remained IL-4 biased. However, only a limited number of CD4 cells appeared in the postchallenge lung, and these were strongly enriched for the Th1 phenotype. Thus, the type of memory T-cell response induced by DNA vaccination does not determine the type of response that will predominate at the site of an infection.

Maternal asthma is associated with reduced female fetal growth

Asthma during pregnancy is associated with a low birth weight, although the mechanisms contributing to this outcome remain unknown. The relationship between maternal asthma and its treatment, placental function, fetal sex, and low birth weight was examined to establish the effect of asthma on fetal growth. Glucocorticoid intake by women with asthma was assessed throughout pregnancy. The placenta was collected after delivery, and 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) activity was measured. Fetal cortisol and estriol were measured in the umbilical vein plasma at delivery. Those with asthma were compared with a nonasthmatic control group. In women with asthma who did not use inhaled steroids and were pregnant with a female fetus, we observed significantly reduced birth weights, whereas male birth weights were unaffected. The presence of a female fetus was associated with significantly increased maternal circulating monocytes, significantly reduced placental 11beta-HSD2 activity and fetal estriol, and a trend toward elevated fetal plasma cortisol. This study provides evidence that in pregnancies complicated by asthma there is a fetal sex-specific effect on the maternal immune system with adverse effects on placental function and female fetal growth.

The effect of liu-wei-di-huang wan on cytokine gene expression from human peripheral blood lymphocytes

Liu-Wei-Di-Huang Wan (LWDHW) has been used by traditional Chinese doctors to treat asthma patients. This study was to examine the potential effect of this decoction on the regulation of T helper (Th)1- and Th2-type cytokine gene expression in vitro. Peripheral blood mononuclear cells (PBMC) were activated with mitogen for 24 hours in the presence or absence of LWDHW extracts. Concentrations of different cytokines in the culture supernatants were determined with ELISA. RNA isolated from cultured cells was subjected to RT-PCR analysis. The results showed that the expression of all cytokines (Th2-type: IL-4, IL-5, IL-10, or IL-13 and Th1-type: IL-2 and IFN-gamma) examined was inhibited at both RNA and protein levels by LWDHW. Since the cell viability was similar in all cultures, the reduction of cytokine production was not due to the toxicity of LWDHW. Moreover, the cells either retained or increased their capacity to respond to mitogen stimulation after incubation with the LWDHW decoction. Therefore, the data suggest that LWDHW functioned directly on cytokine gene expression from activated PBMC.

House dust mite Dermatophagoides farinae augments proinflammatory mediator productions and accessory function of alveolar macrophages: implications for allergic sensitization and inflammation

In this study, we examine the effects of Dermatophagoides farinae (Der f), a major source of airborne allergens, on alveolar macrophages (AMs), and we also test its contribution to allergic responses in mice. Der f activated NF-kappaB of AMs and, unlike OVA or LPS stimulation, up-regulated IL-6, TNF-alpha, and NO. In addition, it down-regulated antioxidants, but affected neither the expression nor production of IL-12. Der f-stimulated AMs expressed enhanced levels of costimulatory B7 molecules, supported T cell proliferation, and promoted Th2 cell development. The enhanced accessory function was suppressed by blockade mAbs to B7.2, IL-6, and TNF-alpha and by N-monomethyl-L-arginine, an NO synthase inhibitor, and N-acetylcysteine, a thiol antioxidant, whereas it was augmented by (+/-)-S-nitroso-N-acetylpenicillamine, an NO donor. Arg-Gly-Asp-Ser peptide and neo-glycoproteins galactose-BSA and mannose-BSA inhibited the Der f-induced IL-6 and TNF-alpha productions and enhanced accessory function of AMs. Der f was more potent than OVA for inducing pulmonary eosinophilic inflammation, NO, and serum allergen-specific IgG1 Ab production in mice. AMs from Der f-challenged mice expressed enhanced levels of B7 and augmented T cell proliferation ex vivo. In Der f-challenged mice, respiratory syncytial virus infection (5 x 10(5) pfu; 3 days before Der f instillation) augmented Der f-specific Ab production, whereas dexamethasone (50 mg/kg; 1 h before Der f instillation) diminished the allergic airway inflammation and Ab response. We conclude that AMs are sensitive targets for Der f and that the Der f-induced proinflammatory responses may represent an important mechanism in mediating the development of allergic sensitization and inflammation.

Normally suppressing CD40 coregulatory signals delivered by airway macrophages to TH2 lymphocytes are defective in patients with atopic asthma

BACKGROUND

We have previously shown that airway macrophages (AMs) from atopic nonasthmatic subjects, but not atopic asthmatic subjects, inhibit T-cell IL-5 production during an allergen-dependent interaction. However, the mechanisms responsible for the IL-5-modulating effect of the AMs are less clear.

OBJECTIVES

The aim of the present study was to define the roles of B7 and CD40 costimulatory signals delivered by AMs in regulating T-cell IL-5 responses in an allergen-stimulated coculture system.

METHODS

Peripheral blood CD4(+) T cells and AMs were cocultured under different conditions.

RESULTS

Compared with those from well-matched atopic nonasthmatic subjects, AMs from atopic asthmatic subjects demonstrated a significantly lower expression of B7-1 and CD40, but not B7-2 and HLA-DR, after either fresh isolation or coculture with allergen-reactive CD4(+) T cells. Lower IL-12 production by the AMs from asthmatic subjects was also observed under the same conditions. Allergen-related T-cell IFN-gamma and IL-5 production was inhibited by the addition of either neutralizing B7-1 or B7-2 antibody to the cocultures in both atopic groups. In contrast, IL-5 production was significantly increased by the addition of blocking CD40 antibody, whereas IL-12 production by the AMs was inhibited. Anti-IL-12 mAb enhanced IL-5 production in the cocultures from atopic nonasthmatic subjects, whereas a dose-dependent suppressive effect of recombinant human IL-12 on IL-5 production was seen in atopic asthmatic subjects.

CONCLUSION

In this coculture model system, lower IL-12 production by AMs and higher IL-5 production by CD4(+) T cells in atopic asthmatic subjects compared with that found in atopic nonasthmatic subjects are related to the lower expression of CD40 rather than B7-1 signals on the AMs from these patients.

Variations in serum levels of interleukin (IL)-1beta, IL-2, IL-6, and tumor necrosis factor-alpha during specific immunotherapy

BACKGROUND

Cytokine production by T helper cells is essential for the induction and maintenance of allergic inflammation in the bronchial mucosa. According to recent views, specific immunotherapy (SIT) favors the differentiation of T lymphocytes into cells of the Th1 rather than those of the Th2 subset.

OBJECTIVE

To determine whether or not SIT induces a decrease in the inflammatory reaction by studying eventual variations in the serum levels of IL-1beta, IL-2, IL-6, and TNF-alpha in allergic subjects during SIT.

METHODS

Serum levels of IL-1beta, IL-2, IL-6, and TNF-alpha were determined before and after 3, 6, and 9 months of SIT by an immunoradiometric assay (IRMA) in 11 adults with perennial allergic asthma and/or rhinitis caused by house dust mites and in 6 nonatopic healthy volunteers.

RESULTS

Median serum IL-1beta and TNF-alpha levels of the patients were significantly higher at baseline than those of the controls and decreased during SIT to values similar to or lower (P < .01) after 6 months of SIT for TNF-alpha than those of the controls. Median serum IL-2, significantly lower at baseline than in the controls, increased during SIT to a level similar to that of the controls. Although the median values of IL-1beta and TNF-alpha in the patients tended to decrease and those of IL-2 to increase during SIT, the differences were not significant; the correlation coefficients (r) of the serum levels of IL-1beta IL-6, and TNF-alpha versus duration of SIT were negative, while that of IL-2 was positive.

CONCLUSIONS

Decreases in median serum IL-1beta and TNF-alpha levels during SIT, together with the increases in serum IL-2 and IL-6, compared with those of the controls furnish evidence supporting a reduction in the inflammatory response in the course of SIT.

Th type 1-stimulating activity of lung macrophages inhibits Th2-mediated allergic airway inflammation by an IFN-gamma-dependent mechanism

In the mucosal immune system, resident dendritic cells are specialized for priming Th2-polarized immunity, whereas the Ag-presenting activity of macrophages has been linked with the development of Th1 phenotype. As an immune switch toward Th1 can protect against Th2-mediated allergic response, this study investigated the capacity of lung macrophages to stimulate Th1 responses during the secondary exposure to inhaled allergen, thereby suppressing Th2-mediated allergic airway inflammation in a murine model of allergic asthma. Following airway macrophage depletion in OVA-sensitized mice, lung T cells defaulted to a phenotype that produced less Th1 (IFN-gamma) and more Th2 (IL-4 and IL-5) cytokines, leading to more severe airway hyperreactivity and inflammation after intranasal Ag challenge. After OVA pulsing and adoptive transfer, lung macrophages selectively promoted a Th1 response in Ag-sensitized recipients and did not induce pulmonary eosinophilia. By contrast, OVA pulsing and adoptive transfer of a lung cell preparation, consisting of dendritic cells, B cells, and macrophages, promoted a Th2 response with an associated inflammatory response that was suppressed when macrophages were present and pretreated with IFN-gamma, but exacerbated when macrophages were depleted before IFN-gamma treatment. In addition, Th1-promoting activity of lung macrophages was not related to the autocrine production of IL-12p40. These results suggest that the Th1-promoting APC activity may be an inherent property of the lung macrophage population, and may play an important role, upon stimulation by IFN-gamma, in antagonizing an ongoing Th2 immunity and Th2-dependent allergic responses.

PBMCs from both atopic asthmatic and nonatopic children show a TH2 cytokine response to house dust mite allergen

BACKGROUND

The hypothesis that in atopic diseases the T-helper response is skewed toward a T(H)2-type cytokine response was based on studies with mitogen stimulation, T-cell clones, or both.

OBJECTIVE

Using primary cultures, we investigated (1) whether atopic asthmatic patients have a T(H)2 response and nonatopic subjects have a T(H)1 response to allergen and (2) whether atopic patients have a decreased ability to mount T(H)1 immune responses to mycobacterial antigens.

METHODS

The responses of PBMCs to allergen (house dust mite [HDM]) or purified protein derivative of Mycobacterium tuberculosis (PPD) stimulation from 10 severely and 14 moderately asthmatic patients (all allergic to HDM) were compared with those of 17 nonatopic healthy black (Xhosa) children.

RESULTS

HDM-stimulated proliferation, IL-5 release, and the IL-5/IFN-gamma ratio were significantly increased in subjects with atopic asthma, whereas IFN-gamma release was not significantly different. IL-4 levels were below the level of detection. PPD-stimulated proliferation, IL-5 release, IFN-gamma release, and the IL-5/IFN-gamma ratio were not significantly different among the groups. Each group had a significantly higher IL-5/IFN-gamma ratio in response to HDM than to PPD (a T(H)1 stimulus).

CONCLUSION

Our study, which used primary cultures to investigate the hypothesis that nonatopic subjects have a T(H)1 response to allergens, indicates that HDM stimulates a T(H)2 cytokine response in both atopic and nonatopic subjects but that the response is enhanced in atopic patients. Our results with PPD suggest that normal and atopic asthmatic subjects can have a T(H)1 cytokine response to mycobacteria, but there is a subgroup of atopic subjects that have a T(H)2 response.

Alveolar macrophages bind and phagocytose allergen-containing pollen starch granules via C-type lectin and integrin receptors: implications for airway inflammatory disease

Recent studies suggest that IgE-independent mechanisms of airway inflammation contribute significantly to the pathophysiology of allergic airway inflammatory diseases such as asthma. Such mechanisms may involve direct interactions between inhaled allergens and cells of the respiratory tract such as macrophages, dendritic cells, and epithelial cells. In this study, we investigated receptor-mediated interactions occurring between alveolar macrophages and allergen-containing pollen starch granules (PSG). We report here that PSG are released from a range of grass species and are rapidly bound and phagocytosed by alveolar macrophages. Human monocyte-derived dendritic cells also bound PSG but no internalization was observed. Phagocytosis of PSG was dependent on Mg2+ and Ca2+ and was inhibited by neo-glycoproteins such as galactose-BSA and N-acetylgalactose-BSA. Partial inhibition of phagocytosis was also seen with the Arg-Gly-Asp-Ser (RGDS) motif and with an anti-CD18 mAb (OX42). The combination of both neo-glycoprotein and anti-CD18 achieved the greatest degree of inhibition (>90%). Together, these data suggest a role for both C-type lectins and beta2-integrins in the binding and internalization of PSG. The consequences of this interaction included a rapid up-regulation of inducible NO synthase mRNA and subsequent release of NO by alveolar macrophages. Thus, receptor-mediated recognition of inhaled allergenic particles by alveolar macrophages may represent a potential mechanism for modulating the inflammatory response associated with allergic airway diseases such as asthma.

The epidemic of asthma: too much allergen or not enough infection?

Asthma has generally been thought to result from exposure to allergens in infancy leading to atopy, and eventually to airway hyperresponsiveness. There is now evidence that implicates absence of childhood infections as a factor in development of asthma. Childhood infections seem to be important in normal maturation of the immune system, with asthma a manifestation of a persistent "immature" immune system.

Airway inflammation and altered alveolar macrophage phenotype pattern after repeated low-dose allergen exposure of atopic asthmatic subjects

BACKGROUND

The alveolar macrophage (AM) constitutes an important link between pulmonary innate and adaptive immunity due to its antigen-presenting capacity and ability to express different immunomodulating mediators. The role of AMs in the pathogenesis of allergic inflammation has yet to be fully determined.

OBJECTIVE

To investigate clinical effects and any change in the AM phenotype pattern after inhalation of sub-clinical doses of allergen by asthmatic patients.

METHODS

Eight subjects with allergic asthma underwent repeated low-dose allergen provocations equivalent to 10% of PD20. AMs recovered with bronchoalveolar lavage (BAL) were characterized by flow cytometric analysis of adhesion molecules, co-stimulatory molecules and markers for AM population activation and heterogeneity.

RESULTS

An allergic airway inflammation, sub-clinical in six out of eight subjects, was obtained after low-dose allergen provocations, as determined by increased airway methacholine reactivity, increased BAL fluid total cell and eosinophil counts and increased serum ECP levels. The AMs showed a post-challenge altered phenotype pattern with a decreased expression of CD11a, CD16, CD71 and HLA class I and an increased expression of CD11b and CD14. The AMs were positive for CD83 and a weak post-challenge increase in the CD83 expression was found.

CONCLUSION

Repeated low-dose allergen exposure induces an allergic airway inflammation in asthmatic subjects. The inflammation is associated with an altered AM phenotype pattern, consistent with an influx of monocytes and a hypothetical increased accessory cell function in the airways, possibly contributing to the development and sustenance of airway inflammation in asthma.