Inflammatory response in induced sputum mononuclear cells from patients with acute exacerbation of asthma

Effect of lipoteichoic acid on IL-2 and IL-5 release from T lymphocytes in asthma and COPD

Susceptibility to infections with gram-positive bacteria, which are an important trigger of exacerbations, is increased in COPD and asthma. Unraveling the underlying mechanisms may help developing therapeutic strategies to reduce exacerbation rates. The aim of this study was to evaluate the effects of lipoteichoic acid (LTA), a danger signal from gram-positive bacteria, on T cell cytokines related to bacterial infection defense in COPD and asthma. T cell populations within peripheral blood mononuclear cells (PBMCs) were ex-vivo activated towards T(H)2/T(C)2 subtypes and subsequently stimulated with LTA. IL-2 and IL-5 concentrations in cell culture supernatants were measured by ELISA comparative between non-smokers (NS), current smokers without airflow limitation (S), smokers with moderate to severe COPD and mild to moderate asthmatics (A) (each n=10). IL-2 and IL-5 baseline levels were without differences between the cohorts. After T cell activation, IL-2 and IL-5 releases were increased in all cohorts, however, for IL-2 this increase was significantly higher in S and by trend in COPD compared to the other groups. LTA time-dependently suppressed IL-2 release in NS, S and COPD but not in A. LTA reduced IL-5 release in COPD and A but not in NS and S. Summarized, LTA reduces T(H)2/T(C)2 cytokines indicating immunosuppressive effects, which are dysregulated in COPD and asthma. This implies a misguided response to gram-positive bacterial infections, which might help to explain the increased susceptibility to bacterial infections in COPD and asthma.

[Time trends of Th1 and th2 cytokines in induced sputum of asthmatic subjects during acute upper respiratory viral infections]

Fundamento

Muchas de las exacerbaciones del asma se deben a infecciones víricas de las vías respiratorias que inducen una interacción de respuestas inmunitarias entre Th1 y Th2. Sin embargo, las tendencias temporales de estas respuestas durante estos fenómenos no se han estudiado con detalle.

Objetivo

Identificar los posibles mecanismos subyacentes de la relación entre las infecciones víricas respiratorias y las exacerbaciones del asma.

Pacientes y métodos

Seleccionamos 40 adultos, de 21–58 años de edad, en 4 grupos: A, sanos; B, sanos con infección vírica; C, con asma leve o moderada, y D, igual que C pero con infección vírica. Durante el curso de una infección vírica aguda de las vías respiratorias superiores se monitorizaron las citocinas Th1 y Th2 en muestras de esputo inducido en individuos por lo demás sanos y en pacientes asmáticos. La interleucina (IL) 4, la IL-5 y el interferón gamma (IFN-γ) se analizaron mediante un método ELISA. Se monitorizaron las puntuaciones de los síntomas de infección vírica y de gravedad del asma. Las tendencias temporales se analizaron mediante la utilización de modelos mixtos lineales.

Resultados

En los grupos C y D los valores de IL-4 e IL-5 fueron mayores que en los grupos A y B. En el grupo B, los valores de IFN-γ y las puntuaciones de síntomas de infección vírica fueron máximos en el día 2 y disminuyeron rápidamente en el día 7, mientras que en el grupo D los valores de IFN-γ y las puntuaciones de síntomas de infección vírica y de asma alcanzaron un máximo mucho más tarde (días 3–5) y disminuyeron lentamente. En el grupo D, los cocientes IL-4 e IL-5:IFN-γ fueron significativamente más altos que en el grupo C.

Conclusiones

Las exacerbaciones del asma inducidas por las infecciones pueden deberse a un deterioro de las respuestas inmunitarias antivíricas Th1. Parece identificarse un intervalo decisivo de 3–5 días para instaurar una intervención terapéutica.

Inflammatory and functional effects of increasing asthma treatment with formoterol or double dose budesonide

Adding a long-acting beta(2)-agonist to inhaled corticosteroids (ICS) for asthma treatment is better than increasing ICS dose in improving clinical status, although there is no consensus about the impact of this regimen on inflammation. In this double-blind, randomized, parallel group study, asthmatics with moderate to severe disease used budesonide (400 mcg/day) for 5 weeks (run-in period); then they were randomized to use budesonide (800 mcg/day--BUD group) or budesonide plus formoterol (400 mcg and 24 mcg/day, respectively--FORMO group) for 9 weeks (treatment period). Home PEF measurements, symptom daily reporting, spirometry, sputum induction (for differential cell counts and sputum cell cultures), and hypertonic saline bronchial challenge test were performed before and after treatments. TNF-alpha, IL-4 and eotaxin-2 levels in the sputum and cell culture supernatants were determined. Morning and night PEF values increased in the FORMO group during the treatment period (p<0.01), from 435+/-162 to 489+/-169 and 428+/-160 to 496+/-173 L/min, respectively. The rate of exacerbations in the FORMO group was lower than in the BUD group (p<0.05). Neutrophil counts in sputum increased in both groups (p<0.05) and leukocyte viability after 48 h-culture increased in the FORMO group (p<0.05). No other parameter changed significantly in either group. This study showed that adding formoterol to budesonide improved home PEF and provided protection from exacerbations, although increase of leukocyte viability in cell culture may be a matter of concern and needs further investigation.

Severe atopic dermatitis is associated with a reduced frequency of IL-10 producing allergen-specific CD4+ T cells

BACKGROUND

Several studies have investigated levels of T-cell-derived interleukin (IL)-10 in individuals with atopic dermatitis, with conflicting results.

AIMS/HYPOTHESIS

In order to address whether stratification of disease severity may help resolve the different findings, the hypothesis was tested that individuals with severe atopic dermatitis have a lower frequency of circulating IL-10-producing, allergen-specific CD4+ T cells than do individuals with mild disease.

METHODS

Using peripheral blood mononuclear cells derived from individuals with severe (n=12) and mild atopic dermatitis (n=10) and from nonatopic controls (n=10), we investigated production by CD4+ T cells of tumour necrosis factor (TNF)-alpha, IL-4, IL-5, IL-13 and IL-10 in response to phorbol myristate acetate/ionomycin and Der p1 allergen.

RESULTS

It was observed that there were significantly higher frequencies of allergen-specific circulating CD4+ T cells producing TNF-alpha- IL-4-, IL-5- and IL-13, and lower frequencies of these cells producing IL-10 in individuals with severe atopic dermatitis compared with mildly affected individuals and nonatopic controls (P<0.01 for all comparisons). Furthermore, the Der p1-specific CD4+ T cells were enriched within the subset of cells positive for cutaneous lymphocyte-associated antigen.

CONCLUSIONS

Analysis of levels of allergen-specific CD4+ T-cell production of IL-10 in relation to disease severity argues in favour of a role for IL-10 in the control of atopic dermatitis.

A Role for IL-10-Mediated HLA-DR7-Restricted T Cell-Dependent Events in Development of the Modified Th2 Response to Cat Allergen

Although high dose exposure to inhaled cat allergen (Fel d 1) can cause a form of tolerance (modified Th2 response), the T cell mechanism for this phenomenon has not been studied. T cell responses to Fel d 1 were characterized in both allergic (IgE(pos)) and modified Th2 (IgE(neg)IgG(pos)) responders as well as serum Ab-negative controls (IgE(neg)IgG(neg)). Fel d 1 stimulated high levels of IL-10 in PBMC cultures from all individuals, with evidence of Th2 and Th1 cytokine skewing in allergic and control subjects, respectively. Using overlapping peptides, epitopes at the N terminus of Fel d 1 chain 2 were shown to stimulate strong T cell proliferation and to preferentially induce IL-10 (peptide 2:1 (P2:1)) or IFN-gamma (P2:2) regardless of the allergic status of the donor. Injection of cat extract during conventional immunotherapy stimulated expansion of IL-10- and IFN-gamma-producing chain 2 epitope-specific T cells along with increased Fel d 1-specific serum IgG and IgG4 Ab. Six of 12 modified responders expressed the major HLA-DRB1 allele, *0701, and both P2:1 and P2:2 were predicted ligands for this allele. Cultures from DR7-positive modified responders produced the highest levels of IL-10 to P2:1 in addition to other major and minor epitopes within chains 1 and 2. In the presence of anti-IL-10 mAb, both T cell proliferation and IFN-gamma production were enhanced in a Fel d 1- and epitope-specific manner. We conclude that IL-10-producing T cells specific for chain 2 epitopes are relevant to tolerance induction, and that DR7-restricted recognition of these epitopes favors a modified Th2 response.

Assessment of T lymphocyte cytokine production in induced sputum from asthmatics: a flow cytometry study

BACKGROUND

Asthma results from a bronchial inflammation in which Th2 lymphocytes play a pivotal role, as shown in invasive bronchial biopsies and broncho-alveolar lavages. Induced sputum (IS) is a non-invasive method of recovery of bronchial cells, which can be repeated in the same patients. However, lymphocyte activation has not been studied in IS to date, because of the low number of T cells recovered. Herein we took advantage of flow cytometry, a method suitable for the study of small cell populations, to assess T cell cytokine production in IS.

OBJECTIVES

(1) To assess induced sputum T cell cytokine production by flow cytometry in asthmatic subjects and controls. (2) To compare the T cell cytokine production between symptomatic and non-symptomatic asthmatics.

METHODS

Thirteen asthmatics and 19 controls were included. Sputum was induced by a hypertonic saline. Sputum cells were stimulated and intracellular IL-13 and IFN-gamma were detected in T cells by flow cytometry.

RESULTS

Stimulation induced an increase of IL-13 and IFN-gamma production by T cells. This increase was higher in asthmatics. IL-13-producing T cells were increased in asthmatics after stimulation. In symptomatic asthma, IFN-gamma-producing T cells were in higher proportion than in controlled asthma.

CONCLUSION

IS T cell cytokine production indicates a basic Th2 bias in asthma, accompanied during symptoms by a Th1-like activation. These results open the field for longitudinal studies of the variation of T cell activation in asthma.

Study of cytokine gene expression in small cell samples: use in induced sputum

Sputum examination is being increasingly used as a non-invasive method for the study of airway inflammation. However, the technical applications of sputum are still limited because of the small number of cells recovered. In attempt to extend applications of sputum examinations, we developed and standardised, the reverse transcriptase-polymerase chain reaction (RT-PCR), a sensitive and specific technique of detection of mRNA, in induced sputum samples. Total RNA were extracted from samples containing as few as 50 to 80,000 cells, using a phenol-chloroform extraction method. RT-PCR was successfully tested on beta-actin, interferon-gamma (IFN-gamma), interleukin-4 (IL-4) and tumour necrosis factor-beta (TGF-beta) genes. This protocol provides a simple technique to extract total RNA from a few number of induced sputum cells. It permits the semi-quantitatively study of cytokine gene expression in airways with simple means.

T cell cytokine profiles in childhood asthma

BACKGROUND

An imbalance of T cell subsets in asthma with a predominance of Th2 type cells has been proposed. The aim of this study was simultaneously to detect surface markers and intracellular production of cytokines in T cells from the airways of children with and without asthma.

METHODS

Bronchoalveolar lavage (BAL) fluid was obtained by wedging a suction catheter into the distal airway immediately before elective surgery. Cells were stimulated with phorbol 12-myristrate 13-acetate (PMA) and ionomycin and intracytoplasmic cytokine retention was achieved using monensin. The cells were stained with the relevant antibodies and analysed by flow cytometry.

RESULTS

No statistical difference was observed between children with atopic asthma, atopic non-asthmatic subjects, and normal controls in the percentage of CD3+ cells producing interleukin (IL)-2 or IL-4. Interferon (IFN)gamma+ T cells were, however, present in a much higher percentage than either IL-2 or IL-4 positive cells. The percentage of IFNgamma+ T cells was significantly increased in subjects with atopic asthma (median 71.3%, interquartile range (IQR) 65.1-82.2, n=13) compared with both atopic non-asthmatic subjects (51.9%, IQR 37.2-70.3, n=12), p<0.05 and normal controls (58.1%, IQR 36.1-66.1, n=23), p<0.01.

CONCLUSIONS

These findings indicate that IFNgamma producing T cells are more abundant in the airways of children with atopic asthma than in atopic non-asthmatic subjects and controls. The proinflammatory activities of IFNgamma may play an important role in the pathogenesis of childhood asthma and may suggest that asthma is not simply a Th2 driven response.