Basophils, eosinophils, and mast cells in atopic and nonatopic asthma and in late-phase allergic reactions in the lung and skin

BACKGROUND

Previous studies used indirect methods to identify basophils in the bronchi in asthma, and the numbers were not compared with eosinophils and mast cells. Furthermore, differences in basophil numbers between atopic and nonatopic asthma at baseline and between late-phase skin and asthmatic reactions have not been previously documented.

OBJECTIVE

The basophil granule-specific mAb BB1 was used to identify basophils in (1) bronchial biopsy specimens from atopic asthmatic subjects and nonatopic asthmatic subjects and control subjects, (2) biopsy specimens from atopic asthmatic subjects before and after inhalational allergen challenge, and (3) late-phase skin reactions. Basophil numbers were compared with EG2(+) eosinophils and tryptase(+) mast cells.

METHODS

Cells were enumerated in bronchial and skin biopsy specimens by means of immunohistochemistry with the alkaline phosphatase-antialkaline phosphatase method.

RESULTS

There were elevated numbers of basophils in baseline biopsy specimens in atopic asthmatic subjects compared with atopic control subjects or normal control subjects, although eosinophils and mast cells were 10-fold higher. There was an intermediate number of basophils in nonatopic asthmatic subjects. Basophils increased after allergen inhalation, but again basophils were less than 10% of eosinophils. In contrast, basophils in cutaneous late-phase reactions were approximately 40% of infiltrating eosinophils. The peak of basophil accumulation was at 24 hours, whereas maximal eosinophil infiltration occurred at 6 hours. One third of cutaneous basophils had morphologic appearances suggestive of degranulation.

CONCLUSION

Numerous basophils infiltrated cutaneous late-phase reactions in atopic subjects. However, this cell was not prominent in bronchial biopsy specimens of asthmatic subjects, either at baseline or after allergen challenge.

Eosinophil chemotactic chemokines (eotaxin, eotaxin-2, RANTES, monocyte chemoattractant protein-3 (MCP-3), and MCP-4), and C-C chemokine receptor 3 expression in bronchial biopsies from atopic and nonatopic (Intrinsic) asthmatics

Atopic (AA) and nonatopic (NAA) asthma are characterized by chronic inflammation and local tissue eosinophilia. Many C-C chemokines are potent eosinophil chemoattractants and act predominantly via the CCR3. We examined the expression of eotaxin, eotaxin-2, RANTES, monocyte chemoattractant protein-3 (MCP-3), MCP-4, and CCR3 in the bronchial mucosa from atopic (AA) and nonatopic (intrinsic; NAA) asthmatics and compared our findings with atopic (AC) and nonatopic nonasthmatic controls (NC). Cryostat sections were processed for immunohistochemistry (IHC), in situ hybridization (ISH), and double IHC/ISH. Compared with AC and NC, the numbers of EG2+ cells and the cells expressing mRNA for eotaxin, eotaxin-2, RANTES, MCP-3, MCP-4, and CCR3 were significantly increased in AA and NAA (p < 0.01). Nonsignificant differences in these variants were observed between AA and NAA and between AC and NC. Significant correlations between the cells expressing eotaxin or CCR3 and EG2+ eosinophils in the bronchial tissue were also observed for both AA (p < 0.01) and NAA (p = 0.01). Moreover, in the total asthmatic group (AA + NAA) there was a significant inverse correlation between the expression of eotaxin and that of the histamine PC20 (p < 0.05). Sequential IHC/ISH showed that cytokeratin+ epithelial cells, CD31+ endothelial cells, and CD68+ macrophages were the major sources of eotaxin, eotaxin-2, RANTES, MCP-3, and MCP-4. There was no significantly different distribution of cells expressing mRNA for these chemokines between atopic and nonatopic asthma. These findings suggest that multiple C-C chemokines, acting at least in part via CCR3, contribute to bronchial eosinophilia in both atopic and nonatopic asthma.

Grass pollen immunotherapy decreases the number of mast cells in the skin

BACKGROUND

Allergen injection immunotherapy is effective for summer hay fever and reduces cutaneous sensitivity to grass pollen.

OBJECTIVE

We have addressed whether this effect of immunotherapy may be due to a decrease in mast cell numbers in the skin.

METHODS

Total mast cells and mast cell subtypes in the dermis were measured by dual immunocytochemistry in 40 adult patients who had received either 'active' grass pollen immunotherapy or placebo injections for 9 months in a double-blind clinical trial.

RESULTS

Clinical improvement in hay fever was accompanied by a greater than 10-fold reduction in the immediate cutaneous response to grass pollen (P = 0. 0002) and a sevenfold decrease in mast cell numbers in the skin (P = 0.0001). The number of mast cells after immunotherapy correlated with the clinical response in terms of seasonal symptoms (r = 0.61, P = 0.001) and rescue medication use (r = 0.75, P = 0.0001). Specific double immunostaining showed that the majority of mast cells (greater than 60%) were tryptase/chymase-positive (MCTC) and the remainder tryptase-only (MCT) cells. Following immunotherapy both subtypes were equally reduced.

CONCLUSION

One mechanism by which immunotherapy may act is to reduce mast cell numbers with a consequent reduction in immediate allergic sensitivity.

Effect of topical corticosteroids on seasonal increases in epithelial eosinophils and mast cells in allergic rhinitis: a comparison of nasal brush and biopsy methods

BACKGROUND

Nasal brushing and nasal biopsy are well-tolerated sampling techniques. Seasonal grass pollen-induced rhinitis is characterized by epithelial mast cell infiltration and seasonal increases in both epithelial and sub-mucosal eosinophils.

OBJECTIVE

To compare the ability of the nasal brush and nasal biopsy techniques to detect natural seasonal increases in eosinophils and mast cells, and to assess the influence of topical corticosteroid.

METHODS

Nasal brush samples and nasal biopsies were collected from 46 grass pollen-sensitive seasonal rhinitis patients before the grass pollen season and at the peak of the pollen season following 6 weeks' treatment with either fluticasone propionate aqueous nasal spray (200 microg, twice daily) or placebo nasal spray.

RESULTS

Placebo patients showed seasonal increases in epithelial eosinophils both with nasal brushing (P < 0.0001) and biopsy (P < 0.001). Epithelial mast cell numbers also increased during the pollen season as detectable by brushing (P < 0.0001) and biopsy (P < 0.03). Changes in cell numbers measured by nasal brushing correlated with those observed with nasal biopsy, both for eosinophils and mast cells (P < 0.05). Sub-mucosal eosinophils but not mast cells also increased during the pollen season (P < 0.002). Nasal brushing and biopsy revealed that fluticasone treatment inhibited seasonal increases in epithelial eosinophils (P < 0.00001) and epithelial infiltration by mast cells (nasal brushing P < 0.00001 and nasal biopsy P < 0.01). Fluticasone also inhibited seasonal increases in sub-mucosal eosinophils (P < 0.001) and significantly reduced nasal symptoms (P < 0.001).

CONCLUSION

Nasal brushing harvests sufficient inflammatory cells from the surface of the nasal mucosa to be used in lieu of nasal biopsies in observation of the effect of drugs on the nasal epithelium.

Anti-T cell strategies in asthma

Chronic asthma is characterised by inflammation of the airways. Although corticosteroids are effective therapy, the risk benefit ratio is unacceptable in a minority of patients requiring chronic and high dose corticosteroid therapy because of adverse effects. There is accumulating circumstantial evidence that the CD4+ T-cell plays a central role in the pathogenesis of chronic asthma. Therapeutic strategies directed specifically at this cell type may offer a novel approach. Controlled clinical trials of cyclosporin A were effective in both chronic asthma and in a model of provoked asthma. Other immunomodulators such as FK506, rapamycin and mycophenolic acid may be useful given their modes of action on the T lymphocyte. The use of monoclonal antibody therapy directed towards these cells and T-cell peptide specific immunotherapy have been evaluated in preliminary studies and demonstrated promising results. Strategies targeting T cell co-stimulatory molecules and T-cell derived cytokines may be of therapeutic utility.

C-C chemokines in allergen-induced late-phase cutaneous responses in atopic subjects: association of eotaxin with early 6-hour eosinophils, and of eotaxin-2 and monocyte chemoattractant protein-4 with the later 24-hour tissue eosinophilia, and relationship to basophils and other C-C chemokines (monocyte chemoattractant protein-3 and RANTES)

The relationship of expression of the C-C chemokines eotaxin, eotaxin 2, RANTES, monocyte chemoattractant protein-3 (MCP-3), and MCP-4 to the kinetics of infiltrating eosinophils, basophils, and other inflammatory cells was examined in allergen-induced, late-phase allergic reactions in the skin of human atopic subjects. EG2+ eosinophils peaked at 6 h and correlated significantly with eotaxin mRNA and protein, whereas declining eosinophils at 24 h correlated significantly with eotaxin-2 and MCP-4 mRNA. In contrast, no significant correlations were observed between BB1+ basophil infiltrates, which peaked at 24 h, and expression of eotaxin, eotaxin-2, RANTES, MCP-3, and MCP-4 or elastase+ neutrophils (6-h peak), CD3+ and CD4+ T cells (24 h), and CD68+ macrophages (72 h). Furthermore, 83% of eosinophils, 40% of basophils, and 1% of CD3+ cells expressed the eotaxin receptor CCR3, while eotaxin protein was expressed by 43% of macrophages, 81% of endothelial cells, and 6% of T cells (6%). These data suggest that 1) eotaxin has a role in the early 6-h recruitment of eosinophils, while eotaxin-2 and MCP-4 appear to be involved in later 24-h infiltration of these CCR3+ cells; 2) different mechanisms may guide the early vs late eosinophilia; and 3) other chemokines and receptors may be involved in basophil accumulation of allergic tissue reactions in human skin.

Increases in eotaxin-positive cells in induced sputum from atopic asthmatic subjects after inhalational allergen challenge

BACKGROUND

Eosinophils are believed to be critical proinflammatory cells in airway mucosal damage in asthma. Eotaxin is a C-C chemokine with selective activity for eosinophils and basophils. Previous studies have shown increased expression of eotaxin in the airways of asthmatics at baseline. We aimed to investigate eotaxin expression during the late-phase reaction to allergen inhalation in atopic asthmatics.

METHODS

Sputum induction was performed before and 24 h after inhalational allergen challenge in atopic asthmatics, and eotaxin protein was detected immunocytochemically.

RESULTS

Thirteen patients with a mean decrease in forced expiratory volume in 1 s of 28% (+/-1.5) during the early asthmatic reaction, and 39% (+/-4.7) during the late asthmatic reaction produced sufficient sputum for study. The percentage of eosinophils in sputum was increased 24 h after allergen challenge (P<0.004), and eosinophil percentages in sputum after challenge correlated with the magnitude of the late-phase reaction (r=0.56, P=0.05). The percentage of eotaxin-positive cells increased from 12.6% (range 2-43.8) to 24.3% (8.1-47.1, P<0.005). Allergen-induced increases in eotaxin-positive cells correlated with increases in eosinophils (r=0.63, P<0.01).

CONCLUSIONS

These findings suggest that eotaxin may contribute to allergen-induced recruitment of eosinophils to the airway in asthmatic subjects.

Immunoglobulin E-independent major histocompatibility complex-restricted T cell peptide epitope-induced late asthmatic reactions

Intradermal administration of short overlapping peptides derived from chain 1 of the cat allergen Fel d 1 (FC1P) that did not cross-link IgE, elicited isolated late asthmatic reactions with no visible early or late cutaneous response in 9/40 cat-allergic asthmatics. Four of the nine were human histocompatibility leukocyte antigen DR13-positive, as compared with only 1/31 nonreactors. The other five reactors expressed either DR1 or DR4. To confirm major histocompatibility complex restriction, fibroblast cell lines transfected with HLA-DR molecules were used to present FC1Ps to cat allergen-specific T cell lines derived from subjects before peptide injection. FC1P3 (peptide 28-44 of Fel d 1 chain 1) was recognized in the context of DR13 alleles (DRB1*1301, 1302) and induced specific T cell proliferation and IL-5 production. T cells from a DR1(+) responder proliferated and produced IL-5 in the presence of FC1P3 and DR1 (DRB1*0101) fibroblast cell lines, whereas T cells from a DR4(+) subject recognized FC1P2 (peptide 22-37) when presented by DRB1*0405. We conclude that short, allergen-derived peptides can directly initiate a major histocompatibility complex-restricted, T cell-dependent late asthmatic reaction, without the requirement for an early IgE/mast cell-dependent response, in sensitized asthmatic subjects.

Eosinophil development and bone marrow and tissue eosinophils in atopic asthma

BACKGROUND

Eosinophils develop from bone marrow (BM) progenitors, and interleukin-5 (IL-5) and eotaxin may act in expansion and mobilisation of BM eosinophils in asthma.

METHODS

We have examined phenotypic changes as CD34+ cells develop to the eosinophil lineage in vitro, and have evaluated BM eosinophils from asthmatic and control subjects for expression of the eotaxin receptor, CCR3.

RESULTS

Acquisition of receptors for IL-5 and CCR3 was an early event in eosinophil development. There were increased CD34+ cells, and mature and immature CCR3+ eosinophils in BM from asthmatics.

CONCLUSION

These data suggest that IL-5 may act early in eosinophil development, and that eotaxin has the capacity to mobilise a BM eosinophil pool in asthma.

T cells and chronic asthma

There is increasing evidence that the asthma process is 'driven' and maintained by persistence of a subset of chronically activated T memory cells, sensitized against allergenic, occupational or viral antigens which 'home' to the lung after antigen exposure or viral infection. In general, allergens induce a CD4 T helper (Th) cell response, whereas viruses recognize CD8+ cytotoxic (Tc) T cells. In the asthmatic airways, there are CD4+ and, to a lesser number CD8+ cells with a type 2 cytokine phenotype (i.e., Th-2 and Tc-2 type). These cells produce interleukin (IL) 3 and 5 and granulocyte-macrophage colony-stimulating factor which recruit, mobilize and activate eosinophils for subsequent mucosal damage, as well as IL-4, an essential cofactor for local or generalized IgE production. This leads to epithelial shedding, mucus hypersecretion and bronchial muscle contraction. Thus, although the eosinophil may damage the mucosal surfaces in asthma, its function appears to be under T cell control. Support for this hypothesis includes: (1) activated T cells and their products can be identified in biopsies from the major variants of the disease (atopic, non-atopic and occupational asthma); (2) colocalization of mRNA for type 2 cytokines to CD4+ and CD8+ cells in atopic and non-atopic asthma; (3) the presence of activated cytokine-producing T cells in corticosteroid-resistant asthma; (4) the association of disease severity with type 2 cytokines, especially IL-5; and (5) the efficacy of cyclosporin A and a monoclonal anti-CD4 in chronic steroid-dependent disease. Inhibitors and/or antagonists directed against more precise T cell associated molecular targets hold promise for the future treatment of chronic asthma.

CD34(+)/interleukin-5Ralpha messenger RNA+ cells in the bronchial mucosa in asthma: potential airway eosinophil progenitors

Eosinophil differentiation is thought to occur by the action of interleukin (IL)-5 on CD34(+) progenitor cells. The allergen-induced increase in eosinophil numbers in isolated airway preparations in vitro, and detection of increased numbers of circulating CD34(+) cells in atopic subjects, led us to the hypothesis that the eosinophil infiltration of the airway in asthma may result from local mucosal differentiation, in addition to recruitment from the bone marrow. We examined CD34(+) cell numbers by immunohistochemistry and IL-5 receptor alpha (IL-5Ralpha) messenger RNA (mRNA) expression by in situ hybridization in bronchial biopsies from atopic asthmatic patients, and from atopic and nonatopic control subjects. CD34(+) cell numbers were increased in the airway in atopic asthmatic and atopic nonasthmatic subjects. In contrast, CD34(+)/ IL-5Ralpha mRNA+ cells were increased in asthmatic subjects when compared with both atopic and nonatopic control subjects. Airway numbers of CD34(+)/IL-5Ralpha mRNA+ cells were correlated to airway caliber in asthmatic subjects and to eosinophil numbers. These findings support the concept that eosinophils may differentiate locally in the airway in asthma.

Increased mature and immature CCR3 messenger RNA+ eosinophils in bone marrow from patients with atopic asthma compared with atopic and nonatopic control subjects

BACKGROUND

Eosinophil infiltration of the bronchial mucosa is characteristic of asthma. Eosinophils differentiate from CD34(+) progenitors. Animal models suggest cooperation between IL-5 and eotaxin to allow rapid mobilization of a pool of bone marrow eosinophils followed by recruitment to the airway mucosa.

OBJECTIVE

The purpose of this study was to enumerate CD34(+) cell numbers in blood and bone marrow from atopic asthmatics and control subjects and to test the hypothesis that there is an increased bone marrow pool of CCR3(+) eosinophils in patients with atopic asthma, as compared with control subjects.

METHODS

Bone marrow aspirates and peripheral blood were obtained from volunteers with asthma and control volunteers. CD34(+) cell numbers were evaluated by flow cytometry, and eosinophil colony-forming activity was evaluated by methylcellulose cultures. Mature eosinophils, eosinophil myelocytes, metamyelocytes, and band forms (immature eosinophils) were enumerated by morphologic findings and immunocytochemistry for eosinophil cationic protein. CCR3 and eotaxin mRNA expression was examined by in situ hybridization, and protein expression was examined by immunocytochemistry. CCR3(+) cells were further identified with Chromotrope 2R staining.

RESULTS

CD34(+) cell numbers in bone marrow were increased in atopic subjects. Numbers of eosinophil colony-forming units in blood and bone marrow did not differ between groups. Percentages of both mature and immature eosinophils were increased in bone marrow from patients with atopic asthma, but not atopic patients with no asthma or normal control subjects. CCR3 was expressed by immature and mature bone marrow eosinophils. Eotaxin was expressed by bone marrow cells from all 3 groups, but there was no increase in subjects with asthma.

CONCLUSION

These findings suggest that in humans there is an increased bone marrow pool of CCR3(+) mature and immature eosinophils available for rapid mobilization in subjects with asthma but not in atopic subjects with no asthma.

Costimulation through CD86 is involved in airway antigen-presenting cell and T cell responses to allergen in atopic asthmatics

Atopic allergic asthma is characterized by activation of Th2-type T cells in the bronchial mucosa. Previous reports have suggested an important role for costimulation through the CD28/CTLA4-CD80/CD86 pathway in allergen activation of T cells in animal models of inhaled allergen challenge. However, human allergen-specific lines and clones were reported to be costimulation independent. We therefore examined CD80 and CD86 dependence of allergen-induced T cell proliferation and cytokine production in peripheral blood and bronchoalveolar lavage from atopic asthmatic subjects and controls. Both allergen-induced proliferation and IL-5 production from PBMC were inhibited by CTLA4-Ig fusion protein and anti-CD86, but not anti-CD80 mAbs. When allergen-specific CD4+ T cell lines from peripheral blood were examined, proliferation and cytokine production were found to be independent of CD80 or CD86 costimulation. However, when cells obtained directly from the airways were examined, allergen-induced proliferation of bronchoalveolar lavage T cells from atopic asthmatic subjects was inhibited by anti-CD86 but not anti-CD80. In addition, bronchoalveolar lavage-adherent cells from asthmatic, but not control subjects showed APC activity to autologous T cells. This was also inhibited by anti-CD86 but not anti-CD80. Thus allergen-induced T cell activation and IL-5 production in the airway in asthmatic subjects is susceptible to blockade by agents interfering with costimulation via CD86, and this may hold therapeutic potential in asthma.

Expression of the IL-4 receptor alpha-subunit is increased in bronchial biopsy specimens from atopic and nonatopic asthmatic subjects

BACKGROUND

Recent studies have provided evidence for increased IL-4 expression in the airways of atopic and nonatopic asthmatic subjects. IL-4 is believed to perform important regulatory roles in asthma; however, the expression of the IL-4 receptor has not been investigated. In this study we examined the mRNA and protein expression of the specific alpha-subunit of the IL-4 receptor (alphaIL-4R) in bronchial biopsy specimens obtained from atopic and nonatopic asthmatic subjects.

METHODS

Asthmatic subjects and nonasthmatic control subjects were recruited, and lung function measurements were performed before bronchoscopy. Endobronchial biopsy specimens were examined for the presence of alphaIL-4R mRNA and immunoreactivity by using in situ hybridization and immunocytochemistry, respectively.

RESULTS

alphaIL-4R mRNA-positive and immunoreactive cells were detected in the epithelium and subepithelium in biopsy specimens from all subjects. Expression of alphaIL-4R mRNA and protein was significantly increased in the epithelium and subepithelium of biopsy specimens from atopic asthmatic subjects compared with atopic control subjects (P <.05 and P <.001, respectively). Epithelial alphaIL-4R mRNA expression and immunoreactivity did not differ significantly between nonatopic asthmatic subjects and nonatopic control subjects. Although the numbers of alphaIL-4R mRNA-positive cells were augmented in the submucosa of intrinsic asthmatic subjects compared with nonatopic control subjects (P <.05), alphaIL-4R immunoreactivity did not differ significantly between these groups. Increased alphaIL-4R immunoreactive signals were also detected in the endothelial cell layer in both atopic and intrinsic asthmatic subjects compared with atopic and nonatopic control subjects, respectively (P <.05). Combined in situ hybridization immunocytochemistry performed on biopsy sections from asthmatic and control subjects demonstrated alphaIL-4R mRNA expression in CD3-positive T cells and tryptasepositive mast cells, with T cells comprising the larger proportion of alphaIL-4R mRNA-positive cells. Numbers of alphaIL-4R mRNA-positive or immunoreactive cells did not correlate with CD3-positive cell numbers, numbers of IL-4 mRNA-positive cells, or indices of pulmonary function.

CONCLUSION

These results demonstrate constitutive alphaIL-4R expression in normal airways and enhanced expression in airway tissue from asthmatic individuals.

Molecular concepts of IgE-initiated inflammation in atopic and nonatopic asthma

Atopic and nonatopic (intrinsic) asthmatics were characterized by a broadly conserved bronchial mucosal proeosinophilic cytokine network in which IL-5 appears to play a key role. Inappropriate IgE-mediated mechanisms may occur in asthma, irrespective of its atopic status, as suggested by elevated serum IgE concentrations and bronchial mucosal expression of FcepsilonRI, IL-4, IL-13, Iepsilon, and Cepsilon. In general, these observations support the concept that these subtypes of asthma, despite showing distinct clinical and biologic features, share many common immunopathologic mechanisms. The most promising future directions of research regarding intrinsic asthma concern the possible identification of novel allergens or antigens, the detailed description of local bronchial mucosal IgE production, and the understanding of a possible macrophage dysfunction. Furthermore, a role for infectious (viral?) or autoimmune processes has yet to be firmly identified in intrinsic asthma. Animal models may also help us to understand the role of IgE and atopy in asthma. Although these are largely IgE-mediated mechanisms, allergen-induced bronchial hyperresponsiveness and eosinophilic inflammation can also occur in the absence of IgE (null mutation of the Cepsilon locus), as shown in a mouse model of hypersensitivity to Aspergillus fumigatus (57). Thus, despite the absence of atopy, IgE-mediated mechanisms may operate in intrinsic asthma (Fig. 1).

Randomised, dose-ranging, placebo-controlled study of chimeric antibody to CD4 (keliximab) in chronic severe asthma

BACKGROUND

There is substantial circumstantial evidence that CD4 lymphocytes have a role in the pathogenesis of chronic asthma. We investigated the efficacy and safety in severe corticosteroid-dependent asthma of a single intravenous infusion of keliximab (IDEC CE9.1), a chimeric monoclonal antibody to CD4.

METHODS

22 patients were recruited from two asthma clinics. In an ascending-dose design, the first eight patients were assigned 0.5 mg/kg keliximab (six) or placebo (two); the next seven were assigned 1.5 mg/kg (five) or placebo (two); and the last seven were assigned 3.0 mg/kg (five) or placebo (two). Masked data on safety for each dose group were assessed before progression to the next dose. Patients kept a daily symptom diary and measured morning and evening peak expiratory flow (PEF) at home. PEF and forced expiratory volume in 1 s (FEV1) were measured at follow-up clinic visits.

FINDINGS

Patients given 0.5 mg/kg or 1.5 mg/kg keliximab and placebo recipients did not differ in change from baseline of PEF, FEV1, or symptom score. Those given 3.0 mg/kg keliximab differed significantly from placebo recipients in change in morning PEF (median area under curve [AUC] 445 vs -82.5, p=0.005) and evening PEF (median AUC 548 vs -85, p=0.014). Symptom score showed the same pattern (though differences did not achieve significance), but there was no difference in clinic FEV1. There were no serious adverse effects related to treatment. Two patients had mild exacerbations of eczema and one developed a transient maculopapular rash. All doses of keliximab were associated with a reduction from baseline in CD4 count.

INTERPRETATION

Our findings raise the possibility that T-cell-directed treatment may be an alternative approach to the treatment of severe asthma.

Nasal eosinophilia and IL-5 mRNA expression in seasonal allergic rhinitis induced by natural allergen exposure: effect of topical corticosteroids

BACKGROUND

Nasal allergen provocation in patients with allergic rhinitis leads to expression of the proeosinophilic cytokines IL-5 and GM-CSF and tissue eosinophilia.

OBJECTIVE

We sought to examine the effect of natural seasonal allergen exposure on IL-5 and GM-CSF mRNA expression and nasal eosinophilia and to evaluate the effects of topical corticosteroid therapy on these responses.

METHODS

Nasal biopsy specimens were collected from 46 grass pollen-sensitive patients with seasonal rhinitis before the grass pollen season. A second biopsy specimen was collected during the pollen season, by which time patients had received 6 weeks treatment with either fluticasone propionate (200 micro(g) twice daily) or placebo nasal spray.

RESULTS

Fluticasone treatment was clinically effective (P <.005). Patients receiving placebo, but not fluticasone, showed increased numbers of epithelial and submucosal EG2+ eosinophils (P <.005) and IL-5 and GM-CSF mRNA-expressing cells (P <.0001) during the pollen season. Colocalization experiments showed that greater than 80% of IL-5 mRNA-expressing cells were submucosal CD3+ T cells in both groups. The numbers of submucosal CD3+ T cells did not increase during the pollen season or decrease with fluticasone treatment. Fluticasone also inhibited IL-5 secretion by grass pollen-stimulated peripheral blood T cells from patients with seasonal rhinitis (n = 5, inhibitory concentration of 50% = 10(-9) to 10(-10) mol/L).

CONCLUSIONS

These results suggest that topical corticosteroids may reduce eosinophilia in seasonal rhinitis by inhibiting T cell IL-5 production.

Unstimulated basophils in atopic and nonatopic subjects express intracellular interleukin-4: detection by flow cytometry

BACKGROUND

IgE-stimulated cultured basophils from atopic subjects are capable of secreting interleukin-4 (IL-4). We describe a flow-cytometric technique which identified intracellular IL-4 in unstimulated basophils unseparated from peripheral blood mononuclear cells (PBMC) in both atopic (AT) and nonatopic (NC) volunteers.

METHODS

Freshly isolated PBMC were fixed in 4% paraformaldehyde (PFA). Surface staining with 22E7, a noncompetitive anti-FcepsilonRI-alpha antibody, allowed identification of basophils. Permeabilization by 0.1% saponin allowed staining of intracellular cytokines with specific monoclonal antibodies (mAbs). Two series of experiments utilizing different protocols and anticytokine mAbs were performed. The first protocol required a two-stage fluorochrome staining technique. The availability of fluorochrome-conjugated mAbs allowed a simpler, one-stage labelling procedure for the second protocol.

RESULTS

With the first protocol, IL-4 (but not IFN-gamma), immunoreactivity was detectable in a majority (median 77%) of peripheral blood basophils from both AT and NC subjects (n=8). Basophil IL-4 immunoreactivity was again evident in experiment 2 but did not differ significantly between AT and NC subjects--either evaluated as percentage of IL-4+ basophils (AT median=66%, NC median=38.4%, P=0.41) or IL-4-specific mean fluorescence (AT median=0.85, NC median=0.3, P=0.07).

CONCLUSIONS

This simple technique allowed the study of intracellular cytokine expression in unstimulated blood basophils. It demonstrated constitutive basophil expression of IL-4 (but not IFN-gamma) in all subjects, with no significant increases in atopics.

Allergen-induced proliferation and interleukin-5 production by bronchoalveolar lavage and blood T cells after segmental allergen challenge

In order to detect and characterize allergen-specific T cells in the airways of atopic asthmatics, we measured proliferation and cytokine production by bronchoalveolar lavage (BAL) T cells isolated from Dermatophagoides pteronyssinus (Der p)-sensitive asthmatics and nonatopic control subjects, and compared the results with those generated using peripheral blood (PB) T cells. BAL and PB mononuclear cells were collected 24 h after segmental allergen challenge by fibreoptic bronchoscopy and venepuncture, respectively. T cells purified from BAL and PB were stimulated with autologous, irradiated antigen-presenting cells and D. pteronyssinus extract or a control, nonallergen antigen (M. tuberculosis purified protein derivative [PPD]). IL-5 and IFN-gamma concentrations were measured in culture supernatants by ELISA, and T-cell proliferation by 3H-thymidine uptake. D. pteronyssinus-induced proliferation of T cells derived from both BAL and PB was elevated in asthmatics when compared with control subjects (p < 0.05), whereas PPD-induced proliferation was equivalent in both compartments. In the asthmatics, D. pteronyssinus-induced proliferative responses of equivalent numbers of BAL and PB T cells obtained after allergen challenge were statistically equivalent. Nevertheless, BAL T cells stimulated with D. pteronyssinus produced significantly greater amounts of IL-5 than did PB T cells (p < 0.05). Allergen-induced proliferation and IL-5 production by BAL T cells in the asthmatics after segmental allergen challenge correlated with the percentages of eosinophils in the BAL fluid (p < 0.01). Further, BAL T cells from asthmatic patients produced significantly higher amounts of IL-5 than did the same number of cells from nonatopic control subjects (p < 0.05). We conclude that, in D. pteronyssinus-sensitive asthmatics, allergen-specific T cells can be detected in the bronchial lumen after allergen challenge and that allergen-induced proliferation and IL-5 production by these cells correlates with local eosinophil influx. Although bronchial luminal T cells show an equivalent proliferative response to allergen stimulation as compared with PB T cells, they do produce more IL-5, consistent with the hypothesis that local differentiation or priming of these cells within the bronchial mucosal environment results in upregulation of allergen-induced IL-5 secretion.

Increases in CD4+ T lymphocytes, macrophages, neutrophils and interleukin 8 positive cells in the airways of patients with bronchiectasis

BACKGROUND

Bronchiectasis is a chronic suppurative lung disease characterised by irreversible dilation of the bronchi and persistent purulent sputum. The immunopathology of the disease was studied using a quantitative immunostaining technique with particular reference to T lymphocytes, macrophages, and granulocytes.

METHODS

Bronchial mucosal biopsy specimens were obtained by fibreoptic bronchoscopy from 12 patients with bronchiectasis (six receiving inhaled steroids) and 11 normal healthy controls. Immunostaining (APAAP method) was performed on frozen cryostat sections with a panel of monoclonal antibodies to total leucocytes (CD45), T lymphocyte phenotypic markers (CD3, CD4, CD8), macrophages (CD68), eosinophils (EG2), and neutrophils (elastase).

RESULTS

There was a mononuclear cell infiltrate in both patients with bronchiectasis and normal controls, but an overall increase in total leucocyte cell numbers (CD45+ cells) was identified in those with bronchiectasis (median values 422 cells/mm2 versus 113 cells/mm2 in control tissue, p < 0.001). Intense infiltration of CD3+ T lymphocytes was observed compared with healthy controls (292 cells/mm2 and 40 cells/mm2, respectively, p < 0.001). This comprised predominantly CD4+ T cells (118 cells/mm2) rather than CD8+ T cells (47 cells/mm2). CD3+ cells counts were reduced in those subjects on inhaled steroids compared with those not receiving inhaled steroids (197 cells/mm2 versus 369 cells/mm2, p < 0.05), as were CD4+ cell counts (82 cells/mm2 versus 190 cells/mm2, p < 0.05). Neutrophil and macrophage cell numbers were also increased in patients with bronchiectasis (114 cells/mm2 and 213 cells/mm2, respectively) compared with controls (41 neutrophils/mm2 and 40 macrophages/mm2). EG2+ (activated) eosinophil numbers were much lower than T cells, macrophages, and neutrophils in patients with bronchiectasis but were increased compared with controls (36 cells/mm2 versus 0 cells/mm2, p < 0.001). In view of the markedly increased neutrophil counts in patients with bronchiectasis, biopsy specimens were immunostained for interleukin 8 (IL-8) which was highly significantly increased compared with controls (47 cells/mm2 versus 15 cells/mm2, p < 0.01). IL-8+ cells were less prominent in steroid treated patients than in patients not receiving treatment (30 cells/mm2 versus 60 cells/mm2, p < 0.05). A further characteristic of bronchiectasis was mucous gland hypertrophy. Gland area comprised up to 40% of the tissue in some bronchiectasis sections while no hypertrophy was noted in control biopsy specimens (p < 0.05).

CONCLUSION

Airway inflammation in bronchiectasis is characterised by tissue neutrophilia, a mononuclear cell infiltrate composed mainly of CD4+ T cells and CD68+ macrophages, and increased IL-8 expression. Inhaled corticosteroid treatment in patients with bronchiectasis is associated with a less marked infiltration by T cells and IL-8+ cells within the bronchial mucosa, although this finding requires confirmation in a prospective placebo controlled trial.

Increased expression of high affinity IgE (FcepsilonRI) receptor-alpha chain mRNA and protein-bearing eosinophils in human allergen-induced atopic asthma

FcepsilonRI receptors play an important role in allergen-induced mediator release and antigen presentation by mast cells, basophils, and monocyte/macrophages in atopic disorders. The expression of FcepsilonRI by tissue eosinophils in atopic asthma after allergen challenge has not been established. For this reason we attempted to identify mRNA and protein product + FcepsilonRIalpha eosinophils in cytospins made from bronchoalveolar lavage (BAL) from atopic asthmatics (n = 9) and nonatopic normal subjects (n = 4) 24 h after segmental challenge with allergen or diluent. Messenger RNA for FcepsilonRIalpha was determined using in situ hybridization and FcepsilonRIalpha protein expression by immunocytochemistry using a mouse monoclonal antibody 22E7. Colocalization of FcepsilonRIalpha receptors to eosinophils was performed using chromotrope 2R. When compared with a control challenge, segmental challenge with Dermatophagoides pteronyssinus induced significant BAL eosinophilia (p = 0.007). The total number of BAL FcepsilonRIalpha mRNA and protein-positive cells also increased in asthmatics, median values 2 (0.7-7.2) and 11.5 (0.6-65.0) x 10(6) cells (p = 0.02) and 0 (0-0.3 x 10(6)) and 3.1 x 10(6) (0.45 - 162.5 x 10(6)) cells (p = 0.007), respectively, for mRNA and protein. Net increases in FcepsilonRIalpha+ cells correlated with the net increases in BAL eosinophils (r = 0.98, p = 0.0001 for mRNA and r = 0.72, p = 0.02 for protein). Colocalization studies with chromotrope 2R revealed that only 4% of FcepsilonRIalpha+ cells were eosinophils after control challenge and, in contrast, 85 to 95% of FcepsilonRIalpha+ cells were eosinophils after allergen. There were no differences in the numbers of FcepsilonRIalpha+ cells or eosinophils in normal control subjects. Our results demonstrated that local endobronchial allergen provocation in atopic asthmatics results in increased synthesis and expression of FcepsilonRIalpha predominantly on BAL eosinophils.

IL-3, IL-5, granulocyte-macrophage colony-stimulating factor receptor alpha-subunit, and common beta-subunit expression by peripheral leukocytes and blood dendritic cells

BACKGROUND

IL-3, IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors consist of cytokine-specific alpha-subunits, which associate with a shared signalling common beta-subunit (beta(c)) to form a high-affinity complex. The expression of IL-3, IL-5, and GM-CSF is upregulated in atopic inflammation, and these cytokines are thought to contribute to pathology through mechanisms that include eosinophil activation.

OBJECTIVE

We sought to examine the distribution of receptor expression between cells relevant to allergic inflammation from individual subjects and to compare atopic and nonatopic individuals.

METHODS

Peripheral blood was obtained from atopic and nonatopic volunteers. Cytokine-receptor expression was examined by flow cytometry with monoclonal antibodies specific for alpha-subunits and beta(c) in combination with phenotypic markers for eosinophils, basophils, neutrophils, dendritic cells, monocytes, and T cells.

RESULTS

Using a ligand-independent system, we confirmed the cellular distribution of IL-5Ralpha, IL-3Ralpha, and GM-CSFRalpha. IL-3Ralpha and GM-CSFRalpha were detected on high-affinity IgE receptor blood dendritic cells. Beta(c) expression was detected on basophils, eosinophils, neutrophils, and, at low levels, on monocytes and dendritic cells. There was intense staining of basophils for IL-3Ralpha relative to IL-5Ralpha, GM-CSFRalpha, and beta(c), whereas eosinophil-staining intensity was similar for IL-3Ralpha, IL-5Ralpha, GM-CSFRalpha, and beta(c). There were no significant differences between atopic and nonatopic subjects in cytokine-receptor staining.

CONCLUSION

IL-3Ralpha and GM-CSRalpha are shown on a newly defined population of Fc(epsilon)RI-high dendritic cells. The intense staining of basophils for IL-3Ralpha, relative to that of IL-5Ralpha and GM-CSFRalpha, is in contrast to eosinophils from the same subjects and may explain the higher sensitivity of basophils to IL-3 compared with IL-5 and GM-CSF. We found no evidence for downregulation of receptor expression in atopic compared with nonatopic subjects, suggesting that these receptors remain accessible as potential targets for therapeutic intervention in atopic allergic disease.