Increasing evidence suggests that alveolar macrophages (AM) are involved in asthma pathogenesis. To better understand the role that these cells play, we investigated the capacity of AM from allergy-resistant rat, Sprague Dawley (SD), to modulate airway hyperresponsiveness of allergy-susceptible rat, Brown Norway (BN). AM of ovalbumin (OVA)-sensitized BN rats were eliminated by intratracheal instillation of liposomes containing clodronate. AM from OVA-sensitized SD rats were transferred into AM-depleted BN rats 24 h before allergen challenge. Airway responsiveness to methacholine was measured the following day. Instillation of liposomes containing clodronate in BN rats eliminated 85% AM after 3 d compared with saline liposomes. Methacholine concentration needed to increase lung resistance by 200% (EC200RL) was significantly lower in OVA-challenged BN rats (27.9 +/- 2.8 mg/ml) compared with SD rats (63.9 +/- 8.6 mg/ml). However, when AM from SD rats were transferred into AM-depleted BN rats, airway responsiveness (64.0 +/- 11.3 mg/ml) was reduced to the level of naïve rats (54.4 +/- 3.7 mg/ml) in a dose-dependent manner. Interestingly, transfer of AM from BN rats into SD rats did not modulate airway responsiveness. To our knowledge, this is the first direct evidence showing that AM may protect against the development of airway hyperresponsiveness.
Comment In: Am J Respir Cell Mol Biol. 2004 Jul;31(1):1-215208095
Comment In: Am J Respir Cell Mol Biol. 2004 Jul;31(1):3-715208096
T lymphocytes may play a regulatory role in the development of allergic airway hyperresponsiveness (AHR). We have studied the relationship between airway responsiveness and a number of immunological changes in Brown-Norway rats sensitized intraperitoneally and repeatedly exposed to ovalbumin (OVA) aerosol. Acetylcholine provocation concentration (PC)150 (the concentration of acetylcholine causing a 150% increase of base-line lung resistance) was measured and peripheral blood and bronchoalveolar lavage (BAL) cells were collected 18-24hr after the final exposure. Total and OVA-specific IgE in serum was measured by enzyme-linked immunosorbent assay (ELISA). Mononuclear cells were analysed by flow cytometry after labelling with monoclonal antibodies against CD2 (pan T-cell marker), CD4, CD8 (T-cell subsets) or CD25 (interleukin-2 receptor). There were significant differences in PC150 (P
Epidemiological data have indicated that some infections are associated with a low risk of allergic diseases, thus supporting the idea (hygiene hypothesis) that the microbial load is an important environmental factor conferring protection against the development of allergies. We set out to test the hygiene hypothesis in a unique epidemiological setting in two socio-economically and culturally markedly different, although genetically related, populations living in geographically adjacent areas. The study cohorts included 266 schoolchildren from the Karelian Republic in Russia and 266 schoolchildren from Finland. The levels of total IgE and allergen-specific IgE for birch, cat and egg albumen were measured. Microbial antibodies were analysed against enteroviruses (coxsackievirus B4), hepatitis A virus, Helicobacter pylori and Toxoplasma gondii. Although total IgE level was higher in Russian Karelian children compared to their Finnish peers, the prevalence of allergen-specific IgE was lower among Russian Karelian children. The prevalence of microbial antibodies was, in turn, significantly more frequent in the Karelian children, reflecting the conspicuous difference in socio-economic background factors. Microbial infections were associated with lower risk of allergic sensitization in Russian Karelian children, enterovirus showing the strongest protective effect in a multivariate model. The present findings support the idea that exposure to certain infections, particularly in childhood, may protect from the development of atopy. Enterovirus infections represent a new candidate to the list of markers of such a protective environment. However, possible causal relationship needs to be confirmed in further studies.
CD26 truncates several chemokines as well as neuropeptides and influences immune responses via modulation of cell adhesion and T cell activation, suggesting an involvement of CD26 in asthmatic and airway inflammation. Therefore, Fischer 344 (F344), Brown Norway (BN) and Lewis (LEW) rat strains, which differ in their CD26-like enzymatic activity, were compared using an asthma model. Additionally, two CD26-deficient mutant F344 rat substrains were included and compared to the wild-type F344 substrain. Immunization was performed twice with ovalbumin (OVA), and 2 weeks later the rats were challenged with OVA intratracheally Flow cytometry (FACS) analysis of different leucocyte subsets as well as enzyme-linked immunosorbent assay (ELISA) for IgE levels in the blood and bronchoalveolar lavage (BAL) were performed 24 h after challenge. LEW rats with the lowest CD26 activity among the rat strains investigated here displayed significantly reduced CD4+ T cell numbers in the BAL compared to wild-type F344 and BN rats. Moreover, in asthma, the ratio of CD26+ to CD26- T cell receptor (TCR)-positive cells increased significantly in F344 and LEW but not BN rats. Most intriguingly, in both CD26-deficient F344 rat substrains the number of CD4+ T lymphocytes was markedly reduced compared to wild-type F344. The decrease in T cell recruitment observed in the CD26-deficient rats was associated with significantly reduced OVA-specific IgE-titres. This is the first report to show a remarkably reduced T cell recruitment in rat strains that either lack or exhibit reduced CD26-like enzymatic activity, suggesting a role for CD26 in the pathogenesis of asthma via T cell-dependent processes such as antibody production.
The ovalbumin (OVA)-induced airway inflammation in rats is a commonly used model to explore the pathobiology of asthma. However, its susceptibility varies greatly between rat strains, and presently Brown Norway (BN) rats are preferentially used. Since recruitment of T cells to the lungs depends on the CD26 (dipeptidyl peptidase IV, DPPIV) expression, Fischer 344 strain (F344) rats are a highly relevant rat strain, in particular because CD26-deficient substrains are available. To establish a F344 rat model of asthma, we challenged F344 rats using different doses of aerosolized antigen (0%, 1%, 2.5%, 5%, and 7.5% OVA) and compared these effects with intratracheal instillation of OVA (1.5 mg/0.3 ml). Asthmoid responsiveness was determined by analysis of early airway responsiveness (EAR), antigen-specific IgE levels, as well as airway inflammation including the composition of T cell subpopulations in the bronchoalveolar lavage (BAL) and lung tissue with special respect to the T cell activation markers CD25 and CD26. Even low allergen doses caused allergen-specific EAR and increases of antigen-specific IgE levels. However, EAR and IgE levels did not increase dose dependently. Higher concentrations of OVA led to a dose-dependent increase of several immunological markers of allergic asthma including an influx of eosinophils, T cells, and dendritic cells. Interestingly, a dose-dependent increase of CD4(+)/CD25(+)/CD26(+) T cells was found in the lungs. Summarizing, we established a novel F344 rat model of aerosolized OVA-induced asthma. Thereby, we found a dose-dependent recruitment of cellular markers of allergic asthma including the activated CD4(+)/CD25(+)/CD26(+) T cell subpopulation, which has not been described in asthma yet.
Transforming growth factor (TGF)-beta is a multifunctional regulator of cell growth and differentiation with both pro- and anti-inflammatory properties. We used an inhibitor of TGF-beta receptor I (TGF-betaRI) kinase, SD-208 (2,4-disubstituted pteridine, a ATP-competitive inhibitor of TGF-betaRI kinase), to determine the role of TGF-beta in airway allergic inflammation and remodeling. Brown-Norway rats sensitized and repeatedly exposed to ovalbumin (OVA) aerosol challenge were orally administered SD-208 twice daily, before each of six OVA exposures to determine the preventive effects, or only before each of the last three of six OVA exposures to investigate its reversal effects. SD-208 (60 mg/kg) reversed bronchial hyperresponsiveness (BHR) induced by repeated allergen exposure, but it did not prevent it. SD-208 prevented changes in serum total and OVA-specific IgE, but it did not reverse them. SD-208 had both a preventive and reversal effect on airway inflammation as measured by major basic protein-positive eosinophils and CD2(+) T-cell counts in mucosal airways, cell proliferation measured by 5-bromo-2'-deoxyuridine expression in airway smooth muscle (ASM) cells and epithelial cells, and goblet cell hyperplasia induced by repeated allergen challenges. There was a significant decrease in intracellular Smad2/3 expression. SD-208 did not significantly decrease the increased ASM thickness induced by allergen exposure. These findings support a proinflammatory and proremodeling role for TGF-beta in allergic airway inflammation. Inhibition of TGF-betaRI kinase activities by SD-208 may be a useful approach to the reversal of BHR and to the prevention and reversal of inflammatory and remodeling features of chronic asthma.
BACKGROUND: There is evidence that the cytokine IL-5 is a prominent feature of airway inflammation in asthma. OBJECTIVE: The aim of this study was to determine whether exogenous IL-5 could cause changes in lung physiology, the early and late airway response after antigen challenge, and airway inflammation in rats that do not have a propensity to develop these changes after sensitization and challenge. METHOD AND RESULTS: Intratracheal administration of IL-5 to ovalbumin sensitized Brown Norway SSN rats increased the airway responsiveness to methacholine (AHR) 20 hours after administration of IL-5 at the same time as an increase in neutrophils occurred in the lung lavage. This effect was dose dependent and was not caused by endotoxin. Concurrent intratracheal administration of 50 ng of anti-IL-5 monoclonal antibody with 10 microg of recombinant human IL-5 decreased the AHR and neutrophil influx. Pretreatment with 3 microg of IL-5 had no effect on the early and late airway response or on AHR after ovalbumin challenge. However, IL-5 increased lung re-sistance 20 hours after antigen challenge. Although total lung cells and differential counts did not differ significantly 8 hours after antigen challenge, the blood lymphocyte CD4/CD8 ratio decreased in IL-5 pretreated rats (P
BACKGROUND: Other researchers have reported that the specific immune response to subsequent antigen challenge is primed in newborn mice or rats dosed orally by gavage. We wanted to investigate if priming of a subsequent specific IgE response could be achieved by dosing newborn rats orally with ovalbumin and if this method could be used in an animal model for food allergy. METHODS: Newborn Brown Norway rats were dosed with ovalbumin in the mouth (100 microg or 6 mg). As young adults, the animals were dosed by gavage for 35 days with 1 mg ovalbumin/day or once intraperitoneally with 100 microg. Control groups were dosed by gavage or intraperitoneally but not as neonates. Additionally, young adult rats were dosed with 1 mg ovalbumin/day in the mouth for 35 days. Sera from individual animals were analysed for specific IgE and specific IgG. RESULTS: In all experiments with neonatal rats the specific IgE and IgG responses were decreased compared to the control groups, however, not always reaching statistical significance. A statistical significant decrease in the specific immune response was found in young adult rats dosed in the mouth as compared to by gavage. CONCLUSIONS: Dosing Brown Norway rats with ovalbumin in the mouth as neonates do not prime the specific immune response. The decrease in immune response found in our experiments when dosing newborn animals in the mouth in opposition to the priming seen by others when dosing by intragastric intubation may be explained by a dissimilar antigen presentation when dosing includes both oral mucosa and gut.
To examine the influence of genetics on the OVA-induced allergic inflammatory response in lungs we compared rats that are genetically Th2-predisposed (Brown Norway, inbred) or not genetically predisposed (Sprague Dawley, outbred). Rats were sensitized with ovalbumin (OVA) and challenged four weeks later with OVA aerosol. Eighteen hours after challenge, lung tissue was studied for evaluation of numbers of eosinophils, neutrophils, macrophages and mast cells, as well as for expression of P-selectin, E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on endothelial cells. From a separate portion of the pulmonary tissue, leucocytes were isolated to analyse numbers of IFNgamma and IL-4 producing cells (ELISPOT assay) and frequencies of T-cell subsets and B cells. We found increased numbers of eosinophils and neutrophils in the lung, an increased number of IL-4 producing cells in lung cell isolates and increased levels of serum (OVA- specific)-IgE in both rat strains. In addition, expression of E-selectin and ICAM-1 was up regulated in both rat strains whereas expression of VCAM-1 was only up regulated in the BN rat. Although the 'allergic' Th2 response to OVA was detectable in both rat strains, it was more pronounced in the BN rat than in the SD rat. However, the SD rat, which is not predisposed to respond in either a Th2 or Th1-like way, appeared capable of mounting an allergic response to OVA. This suggests that other factors than genetic contribute to allergic disease.