Late cutaneous allergic responses in isolated IgE-dependent reactions

Nasal response to a single antigen challenge in patients with allergic rhinitis - inflammatory cell recruitment persists up to 48 hours

BACKGROUND

Allergen challenge in some patients with respiratory allergy is followed by an early and a late reaction.

OBJECTIVE

To evaluate the duration of mediator release and inflammatory cell recruitment during the late antigen-induced nasal response.

METHODS

Eight patients with seasonal allergic rhinitis due to grass pollen underwent local challenge with the relevant allergen, a non-relevant allergen (Parietaria judaica), and nebulized saline solution. Nasal lavages were performed at baseline and 6, 24, 48, 72 h after challenge. Eosinophil cationic protein (ECP), leukotriene C4 (LTC4), leukotriene B4 (LTB4) myeloperoxidase (MPO) and prostaglandin D2 (PGD2) levels were radioimmunoassayed and histamine concentration was measured by an automated fluorometric method.

RESULTS

Nasal challenge with the relevant antigen induced a response 6 h after stimulation, which subsided within 24 h. Eosinophilia, observed in the nasal lavages collected from 6 to 24 h after this challenge, was accompanied by ECP release. Neutrophilia were found in the nasal lavages collected from 6 to 24 h after challenge. The increase in neutrophil number correlated with MPO levels and LTB4 concentrations, but not with the intensity of nasal obstruction. Antigen challenge also induced significant recruitment of mononuclear cells 48 h after provocation. The challenge significantly raised histamine, but not PGD2, levels in the nasal lavages collected 6 h after provocation. A trend towards an increase in LTC4 levels in the nasal lavages collected 6 h after specific antigen challenge was also found. Nasal challenge with a non-relevant allergen or with saline solution did not cause either inflammatory cell recruitment or mediator release.

CONCLUSION

Nasal challenge with the relevant antigen can induce a late response characterized by local accumulation of eosinophils, neutrophils and mononuclear cells persisting for 48 h and accompanied by release of ECP, MPO, LTB4 and histamine. These results indicate that a single antigen challenge in patients with allergic rhinitis causes prolonged inflammatory alterations which may contribute to the development of airway hyperreactivity.

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.

Chemical mediators in atopic dermatitis: involvement of leukotriene B4 released by a type I allergic reaction in the pathogenesis of atopic dermatitis

BACKGROUND

The mediators produced from a type I allergic reaction have not yet been able to explain the pathogenesis of atopic dermatitis (AD).

OBJECTIVE

The purpose of this study was to elucidate the involvement of leukotriene (LT) B4 produced from a type I allergic reaction in the pathogenesis of AD.

METHOD

The release of LTB4 was measured both in vitro, in passively sensitized and antigen-challenged human skin slices, as well as in vivo, in skin chambers on patients with AD.

RESULTS

LTB4 was released from in vitro human skin by stimulation of the antigen (54.9 +/- 14.6 pg/g wet weight of skin by antigen challenge and 28.0 +/- 11.1 pg/g in control skin, P <.002). Antigen-specific release of LTB4 and histamine was also observed in vivo in nonlesional skin from the patients with AD by using the skin chamber technique.

CONCLUSION

LTB4 release during type I allergic reaction in human skin has been determined in vitro. The released LTB4 possibly contributes to cellular response at the acute inflammatory lesion of AD.

Macrophage Colony-Stimulating Factor Stimulates Synthesis and Secretion of a Mouse Homolog of a Human IgE-Dependent Histamine-Releasing Factor by Macrophages In Vitro and In Vivo

Treatment of murine resident peritoneal macrophages with macrophage-CSF (M-CSF) up-regulated the synthesis of a discrete set of proteins, including a 26-kDa protein (p26). The sequence of 20 NH2-terminal amino acids of the purified p26 was identical with the mouse homolog of a human IgE-dependent histamine-releasing factor (HRF). Among macrophage activators tested (M-CSF, granulocyte-macrophage-CSF, IL-3, TNF-α, IFN-γ, and LPS), only M-CSF could up-regulate the p26 HRF synthesis by cultured macrophages. M-CSF not only increased the levels of p26 HRF mRNA and protein, but also stimulated the secretion of an N-glycosylated p26 HRF with a m.w. of 30 kDa. Repeated injections of M-CSF into mouse peritoneal cavity for 4 days elicited macrophages expressing abundant p26 HRF. A single i.p. injection of M-CSF failed to increase the p26 HRF level in peritoneal macrophages of thioglycollate-, LPS-, or adjuvant-treated mice, while M-CSF challenge to OVA-immunized mice caused macrophage infiltration and overproduction of p26 HRF, similarly as did OVA challenge. The Ag-specific priming for enhanced synthesis and secretion of p26 HRF by M-CSF was also demonstrated in cultured macrophages prepared from OVA-immunized mice. An i.p. injection of M-CSF or recombinant p26 HRF triggered eosinophil recruitment, even in the absence of the Ag, in the sensitized mice, but not in normal mice. Furthermore, recombinant p26 HRF could induce eosinophilia without marked macrophage and lymphocyte infiltrations. Our results suggest that p26 HRF secreted by M-CSF-stimulated macrophages may be an important mediator for the late phase allergic inflammation.

Molecular basis of allergic diseases

This review examines our current understanding of the mechanisms underlying allergic diseases. The IgE molecule plays a central role in the pathogenesis of immediate hypersensitivity reactions by virtue of its capacity to bind specifically to high-affinity IgE receptors on mast cells and mediate the release of various mast cell-derived mediators and proinflammatory cytokines on exposure to allergen. Clinically significant allergic responses are followed by a late-phase response dominated by eosinophils and T lymphocytes. The majority of T cells in allergic responses are memory T cells secreting helper type 2 (TH2)-like cytokines, i.e., interleukin (IL)-4, IL-5, IL-13, but not interferon-gamma. These cytokines regulate IgE synthesis and promote eosinophil development, thus contributing to allergic inflammatory responses. Failure to control immune activation early in the course of allergic disease blunts responses to glucocorticoid therapy and contributes to disease progression. The identification of key cells and molecules involved in the initiation and maintenance of allergic inflammation is likely to become an important target in the treatment of this common group of illnesses.

High-affinity immunoglobulin E receptor (Fc epsilon RI)-bearing eosinophils, mast cells, macrophages and Langerhans' cells in allergen-induced late-phase cutaneous reactions in atopic subjects

We have used in situ hybridization (ISH) and immunohistochemistry (IHC) to investigate the kinetics of the expression for Fc epsilon RI mRNA (alpha-, beta- and gamma-chains), the alpha-chain protein product, as well as the phenotype of the mRNA- or protein-positive cells in allergen-induced late-phase skin reactions in atopic subjects. Compared with diluent controls, there were significant increases in the total number of mRNA+ cells for the alpha-, beta- and gamma-chains for Fc epsilon RI at all time-points (6, 24 and 48 hr) after allergen challenge (P < 0.01). By double IHC/ISH significant increases in alpha-, beta- and gamma-chain mRNA+ macrophages, eosinophils, mast cells and CD1a+ cells were also observed after allergen challenge (P < 0.05). The distribution of Fc epsilon RI subunit (alpha-, beta-, or gamma-chain) mRNA+ co-localization was CD68+ macrophages (42-47%), EG2+ eosinophils (33-39%), tryptase+ mast cells (5-11%) and CD1a+ Langerhans' cells (2-4%). Using single IHC, significant increases in the total number of Fc epsilon RI protein+ cells (P < 0.01) were observed 24 and 48 hr after allergen challenge. Double IHC showed that the distribution of Fc epsilon RI+ cells was tryptase+ mast cells (33%), CD68+ macrophages (36%), EG2+ eosinophils (20%), CD1a+ Langerhans' cells (4%) and unidentified cells (7%), at the 24-hr allergen-challenged sites. These observations suggest that the cutaneous late-phase reaction in man is associated with up-regulation of Fc epsilon RI on eosinophils, macrophages, mast cells and Langerhans' cells.

Atopic dermatitis and food hypersensitivity reactions

OBJECTIVE

To determine the role of food hypersensitivity in atopic dermatitis and to determine whether patients with atopic dermatitis who had food hypersensitivity could be identified by screening prick skin tests using a limited number of food allergens.

STUDY DESIGN

Patients with atopic dermatitis attending the Arkansas Children's Hospital Pediatric Allergy Clinic underwent allergy prick skin testing to a battery of food antigens. Patients with positive prick skin tests underwent double-blind, placebo-controlled food challenges.

RESULTS

One-hundred sixty-five patients were enrolled and completed the study. Patients ranged in age from 4 months to 21.9 years (mean 48.9 months). Ninety-eight (60%) patients had at least one positive prick skin test. A total of 266 double-blind, placebo-controlled food challenges were performed. Sixty-four patients (38.7% of total) were interpreted as having a positive challenge. Seven foods (milk, egg, peanut, soy, wheat, cod/catfish, cashew) accounted for 89% of the positive challenges. By use of screening prick skin tests for these seven foods we could identify 99% of the food allergic patients correctly.

CONCLUSIONS

This study confirms that most children with atopic dermatitis have food allergy that can be diagnosed by a prick skin test for the seven foods.

Immunologic basis of chronic allergic diseases: clinical messages from the laboratory bench

During the past decade there have been significant advances in our understanding of the mechanisms underlying allergic responses. Immediate hypersensitivity reactions are mediated primarily by mast cells in an IgE-dependent manner. After the local release of various mediators, proinflammatory cytokines, and chemokines, there is a cell-mediated response that is dominated by eosinophils and T lymphocytes. The majority of T cells in early allergic reactions are memory T cells secreting helper type 2 (TH2)-like cytokines, i.e. IL-4, IL-5, and IL-13, but not interferon-gamma. These cytokines regulate IgE synthesis and promote eosinophil differentiation and cell survival, thus contributing to allergic inflammatory responses. Failure to control immune activation early in the course of allergic inflammation may blunt the response to glucocorticoid therapy and contribute to long-term morbidity of disease. The identification of key cells and cytokines involved in the initiation and maintenance of allergic inflammation is likely to become an important therapeutic target in the future management of this important group of diseases.

Clinical applications of cytokines: new directions in the therapy of atopic diseases

OBJECTIVES

This review will enable the readers to understand the pathogenesis of allergic inflammation, and the role of various cells and cytokines in allergic diseases. Pathogenic cytokines may become key therapeutic targets in the future treatment of allergic diseases.

DATA SOURCES

MEDLINE literature search limited to the English language was performed using the relation between specific cytokines and allergic inflammation as well as therapy of allergic diseases. Relevant articles referenced in retrieved sources and current texts on ctyokines and allergic responses were also utilized.

RESULTS

The mechanism underlying allergic inflammation involves complex interactions between various cells and cytokines. The immediate reaction is caused mainly by mast cells and followed by a cell mediated response that involves eosinophils, mononuclear cells, neutrophils, T lymphocytes and macrophages. The majority of T cells in early allergic reactions are T helper type 2 (TH2)-like producing IL-4, IL-5, IL-13 but not IFN-gamma. These cytokines regulate IgE synthesis, promote eosinophil differentiation and survival, and induce vascular endothelial adhesion molecules, thus contributing to allergic inflammation.

CONCLUSIONS

Although studies of cytokine modulation have utilized animal models of allergic diseases, the increasing availability of recombinant cytokines and cytokine antagonists is likely to lead to more wide scale applications in allergic diseases.

Levels of Eosinophil Cationic Protein and Myeloperoxidase from Chronic Middle Ear Effusion in Patients with Allergy and/or Acute Infection

BACKGROUND AND OBJECTIVE: Allergy may play a role in the middle ear inflammation that leads to otitis media with effusion. The purpose of this study was to determine whether an elevated mediator correlated with the patient's disease and thus could be used to differentiate allergy vs. infection as the cause of the middle ear inflammation.

METHODS: We evaluated 57 individuals with otitis media with effusion, 32 with persistent effusion but no recent acute infection, 14 with recent infection and purulent otitis media with effusion, and 11 healthy subjects. The mediator activity of eosinophils and neutrophils in effusion was studied in patients characterized as having allergy by positive intradermal skin test results and positive radioallergosorbent test results. Eosinophils were characterized by measurement of eosinophil cationic protein in the effusion. Neutrophils were characterized by measurement of myeloperoxidase in the effusion. The levels of eosinophil cationic protein and myeloperoxidase in patients with and without allergy were correlated to patient history.

RESULTS: Significantly elevated levels of both eosinophil cationic protein and myeloperoxidase indicated that inflammation in the ear of patients with otitis media with effusion was characterized by a pronounced involvement of both eosinophils and neutrophils. Eighty-nine percent of all patients with disease had allergy. A higher ratio of myeloperoxidase to eosinophil cationic protein in patients with purulent otitis media with effusion indicated that in patients with a superimposed acute infection, neutrophil activity was increased even further. The level of eosinophil cationic protein was elevated only during the effusion of patients with allergies as compared with controls ( p < 0.01). Among 29 cases of nonpurulent otitis media with effusion, 96.5% had allergic immune-mediated disease proved by skin testing, which was related clinically to their ear disease. Eighty-nine percent (89.6%) of these patients had eosinophil cationic protein levels greater than 10 μg/L.

CONCLUSION: Middle ear eosinophil cationic protein may be used as a marker of related allergy.

Passive transfer of immediate hypersensitivity and airway hyperresponsiveness by allergen-specific immunoglobulin (Ig) E and IgG1 in mice

In a proportion of atopic asthmatics, exposure to a relevant antigen is followed by chronic inflammation in the airways leading to altered airway responsiveness (AR). However, the mechanisms underlying the development of airway hyperresponsiveness still remain unclear. To elucidate the relationship between IgE-mediated reactions and airway hyperresponsiveness, a murine model of passive sensitization and airway challenge with ovalbumin (OVA) was developed using anti-OVA IgE and IgG antibodies from murine B cell hybridomas. Passive sensitization by intravenous injection of anti-OVA IgE resulted in immediate cutaneous hypersensitivity and, after airway challenge with OVA on two consecutive days, increased AR in BALB/c and SJL mice. Increased numbers of eosinophils were observed in bronchoalveolar lavage fluid, in cells extracted from the lungs, and in the peribronchial areas of BALB/c mice passively sensitized with IgE and challenged through the airways compared with nonsensitized mice. Eosinophil peroxidase activity was also elevated in lung tissue from these mice. Passive sensitization with anti-OVA IgG1 but not IgG2a or IgG3 was similarly associated with development of skin test reactivity and increased AR after airway challenge, accompanied by an increase in eosinophils in bronchoalveolar lavage fluid. These data suggest that IgE/IgG1-mediated reactions together with local challenge with antigen can result in allergic inflammation resulting in altered airway function.

Effect of cetirizine and prednisolone on cellular infiltration and cytokine mRNA expression during allergen-induced late cutaneous responses

BACKGROUND

The ability of cetirizine to inhibit eosinophil infiltration into the sites of allergen-induced cutaneous late-phase reactions is controversial. A previous skin biopsy study gave negative results with 15 mg of cetirizine as a single dose.

OBJECTIVE

To confirm these findings we have used cetirizine (30 mg daily) for 5 days and compared the results with prednisolone (20 mg daily for 5 days) as a positive control. The effect of these agents on mRNA positive cells for interleukin-3 (IL-3), interleukin-4, interleukin-5 and granulocyte/macrophage-colony stimulating factor (GM-CSF) was also evaluated.

METHODS

A double-blind, placebo-controlled cross-over study (n = 12) was followed. After each treatment 30 biological units (BUs) of Dermatophagoides pteronyssinus or Phleum pratense were injected intradermally and the early (15 min) and late-phase response sizes (6 and 24 h) were measured. Skin biopsies were taken at 24 h for immunocytochemistry and in situ hybridization.

RESULTS

Cetirizine but not prednisolone inhibited the early-phase response (37%, P = 0.004). In contrast prednisolone, but not cetirizine, significantly inhibited the size of the late-phase reaction at 24 h (70%, P = 0.021). This was associated with significant decreases in total (MBP+) and activated (EG2+) eosinophils (P = 0.019 and 0.014, respectively), as compared with placebo. There were also clear but non-significant reductions in interleukin-3, interleukin-4, interleukin-5 and granulocyte/macrophage-colony stimulating factor mRNA+ cells.

CONCLUSION

Prednisolone, but not cetirizine, inhibited both the magnitude of the allergen-induced late-phase response and the accompanying local eosinophil infiltration. These corticosteroid effects were associated with a reduction in cells expressing mRNA for 'TH2-type' cytokines.

Food allergy in atopic dogs

The food sensitive dog provides a good animal model for food allergy, whose allergic reaction can be followed serially with repeated challenges both in skin and by oral challenges and by endoscopic direct visualization and serial biopsies. This model is proving useful in showing reduced allergenicity in food allergens-soy, wheat, cow's milk by thioredoxin treatment. Recently Dr. Buchanan has cloned the gene for the NADP-thioredoxin reductase (NTR) which he transferred into barley seeds with a bacterial vector. He is attempting to do the same with wheat and soy seeds to produce genetically hypoallergenic foods. The canine model for food allergy provides an excellent model in which to test such bio-engineered potentially hypoallergenic foods.

Immunohistological comparison of granulated cell proteins in induced immediate urticarial dermographism and delayed pressure urticaria lesions

Urticarial dermographism and delayed pressure urticaria are two forms of physical urticaria which are well defined clinically and histologically. Previous studies have shown eosinophil granule protein deposition in urticarial reactions, including chronic urticaria, solar urticaria and delayed pressure urticaria. To evaluate and compare the involvement of granulated inflammatory cells in urticarial dermographism and delayed pressure urticaria, we studied sequential biopsies of induced lesions of urticarial dermographism and delayed pressure urticaria by indirect immunofluorescence, to detect eosinophil granule major basic protein (MBP) and neutrophil granule elastase. Biopsies from dermographic lesions at time 0, 5 min, 15 min, 2 h and 24 h, showed few infiltrating eosinophils, with minimal extracellular MBP deposition, and a few infiltrating neutrophils, with minimal neutrophil elastase deposition, throughout the evolution of the lesions. Sequential biopsies of delayed pressure urticaria at time 0, 20 min, 6, 12 and 24 h, showed eosinophil infiltration with extensive MBP deposition beginning at 20 min, and neutrophil infiltration with variable elastase deposition beginning at 20 min. Control tissue specimens from normal volunteers showed neutrophil infiltration and slight degranulation, but no eosinophil infiltration or degranulation. Comparison of urticarial dermographism with delayed pressure urticaria showed marked differences in the patterns of infiltration. Delayed pressure urticaria, with eosinophil and neutrophil degranulation, was strikingly similar to the IgE-mediated late phase reaction. In contrast, eosinophil and neutrophil involvement in urticarial dermographism was minimal. Considering the extent of eosinophil granule protein deposition and the biological activities of the eosinophil granule proteins, the findings in delayed pressure urticaria point to an important pathophysiological role of eosinophils in the disease.

Relationship between oral challenges with previously uningested egg and egg-specific IgE antibodies and skin prick tests in infants with food allergy

BACKGROUND

Positive skin prick test (SPT) and RAST reactions to egg that had never previously been ingested have been observed in infants with food allergy. The likelihood of having clinical hypersensitivity reactions when egg is first ingested and the predictive value of SPT and RAST remain to be elucidated.

OBJECTIVE

We investigated the relationship between egg-specific IgE antibodies and positive SPT reaction to egg, and the development of clinical hypersensitivity on the first exposure, in infants with food allergy.

METHODS

The patient group consisted of 21 infants with food allergy and positive SPT and/or RAST reaction to egg, which they had never previously ingested; the control group of 12 infants had food allergy and negative test results. All subjects underwent double-blind placebo-controlled food challenges with egg.

RESULTS

Thirteen of 21 patients (61%) and one of 12 control subjects (8%) had positive reactions to challenges (p < 0.01). Thirteen positive reactions to challenges (93%) elicited immediate symptoms. Late-onset eczema occurred in two children. SPT results showed a high sensitivity (0.92) and negative predictive accuracy (0.92), whereas specificity (0.57) and positive predictive accuracy (0.61) were poor. RAST did not have any diagnostic advantage over SPT.

CONCLUSIONS

In infants with food allergy SPT with egg may be helpful in predicting which patients will react to the first exposure.

Type III allergy skin testing. Position statement for EAACI Subcommittee on Skin Tests and Allergen Standardization

Immune-complex-mediated hypersensitivity has been implicated in a small number of allergic respiratory conditions. These include EAA and ABPA. In addition, there is some evidence of type IV hypersensitivity in EAA and BFL, together with activation of complement via the alternative pathway (4, 8, 26). Positive immediate skin tests are now usually regarded as an essential criterion for the diagnosis of ABPA. These reflect the presence of antigen-specific IgE, but this test is not specific for ABPA, as other atopic subjects may also be sensitized to A. fumigatus without any evidence of the parenchymal features that are required to diagnose ABPA. For FL, skin tests with currently available antigens show poor discrimination between affected patients and exposed but healthy individuals. There is little evidence that vascular deposition of immune complexes in the skin contributes to the delayed skin responses in EAA, and skin tests in FL are not specific for type III hypersensitivity. Further refinement of methodology and antigen extracts may improve the specificity of skin tests in FL, but in many cases the aetiology of EAA is multifactorial and the true causative antigens may not have been identified. Therefore, the diagnosis of EAA remains based on history and clinical findings, supported by the presence of precipitins, and sometimes by bronchial biopsy and lavage appearances (25).

Interleukin 5 expressing allergen-specific T-lymphocytes in patients with house dust mite sensitization: analysis at a clonal level

Interleukin 5 (IL-5) is a T-cell lymphokine known to stimulate development, functional activity, and in vitro survival of eosinophils. Tissue and blood eosinophilia occurring during allergic responses of the immune system are potentially mediated by IL-5 secreting T-cells. To test this hypothesis a series of allergen-specific T-cell clones were established from peripheral blood and skin lymphocytes of patients with atopic dermatitis and house dust mite sensitization. In addition, alloreactive T-cell clones were also prepared from peripheral blood lymphocytes of healthy donors. Cloned T-cells were analyzed for IL-5 mRNA expression and IL-5 secretion by means of in vitro gene amplification using the reverse transcriptase polymerase chain reaction and IL-5 specific oligonucleotide hybridization, as well as IL-5-specific ELISA. A majority of allergen-specific long-term cultured T-cell clones (84%) of different donors and of either phenotype (CD8+ or CD4+) disclosed IL-5 transcripts on stimulation with lectins. Almost all clones exhibiting IL-5 transcripts also released immunoreactive IL-5 protein into their culture supernatants. In contrast, only 2% of alloreactive T-cell clones obtained from healthy donors and none of alloreactive T-cell clones of one atopic patient investigated expressed detectable amounts of IL-5 mRNA in response to lectin stimulation, all of whom were CD4+. These results suggest that eosinophilia observed in allergic responses in the peripheral blood and in tissues at the site of induced late-phase cutaneous reaction may be associated with IL-5 release by allergen-specific T-cells.

A beta 2-agonist, procaterol, inhibits basophil migration

Beta 2-receptor agonists have recently been reported to be effective on allergen-induced late-phase reaction (LPR) in addition to their inhibitory effect on immediate-phase reaction, although the precise mechanism is not fully understood. In this study, we tested the effect of a selective beta 2-agonist, procaterol, on human basophil migration, which may be an important characteristic of LPR. Procaterol inhibited IL-8- and C5a-induced basophil migration in a dose-dependent fashion; 10(-7) M of procaterol reduced 30% of migration induced by both factors. The action of procaterol was rapid since the inhibition of migration was detected without preincubation and was not via the toxic effect on basophils as assessed by trypan blue test. The results of this study extend the repertoire of anti-inflammatory actions of beta 2-agonists.

Mechanisms of the human allergic response. Clinical implications

During the past decade, there have been enormous strides made in our understanding of the mechanisms underlying the human allergic response. In particular, interleukin-4 and interleukin-5 play a critical role in this process. This article details the understanding of the mechanisms underlying the regulation of allergic response, which is critical to the development of new treatment of allergic diseases.

Assessment of eosinophil and neutrophil participation in atopic dermatitis: comparison with the IgE-mediated late-phase reaction

We hypothesized that repeated IgE-mediated late-phase reactions are critical in the pathogenesis of atopic dermatitis (AD). Prior studies have shown that extracellular deposition of eosinophil granule major basic protein (MBP) occurs in lesional AD skin, despite a paucity of infiltrating eosinophils, and that deposition of both neutrophil and eosinophil granule proteins occurs in the IgE-mediated late-phase reaction. We evaluated the participation of both eosinophil and neutrophil granule proteins in AD. Cutaneous biopsy specimens and serum and urine samples were obtained from 22 patients with AD. Lesional tissue was examined by means of immunofluorescence for neutrophil elastase and lactoferrin and for eosinophil granule MBP, eosinophil-derived neurotoxin (EDN), and eosinophil cationic protein (ECP). Serum levels of elastase, MBP, EDN, and ECP and urine levels of MBP, EDN, and ECP were measured. Marked extracellular deposition of at least one of the eosinophil granule proteins was present in the dermis of 15 of the 22 AD skin specimens, but minimal or no extracellular neutrophil elastase or lactoferrin deposition was observed in any specimens. Serum and urine levels of MBP, EDN, and ECP in the patients were elevated when compared with those of normal controls, whereas serum levels of neutrophil elastase were not elevated. Serum MPB levels correlated with extent of body surface involvement. These results suggest that eosinophil degranulation occurs in AD but that neutrophil degranulation does not. Although eosinophil degranulation is prominent in both the late-phase reaction and in AD, the lack of neutrophil degranulation in AD demonstrates differences in the inflammatory reactions.

Dexamethasone inhibits basophil migration

Glucocorticoids have been shown to inhibit the local accumulation of basophils during the allergen-induced late-phase reaction (LPR). Since migration is an essential step in the recruitment of basophils from the circulation, we examined whether the widely used glucocorticoid, dexamethasone (DEX), directly acts on basophils to inhibit the migration caused by C5a, interleukin (IL)-3, and IL-8. When purified basophils were preincubated with various concentrations of DEX, a dose-dependent inhibition was observed; DEX at concentrations as low as 1 nM reduced the number of migrated basophils by 30-40%; at higher concentrations, it showed a slightly stronger inhibitory effect. There was no significant difference in the effect of DEX on the migration caused by the three chemoattractants. The action of DEX took place rapidly; apparent inhibition was observed even when migration was initiated without preincubation. Although the inhibitory effect of this agent was not reversed when DEX was removed by washing, the inhibition was not mediated by the toxicity as measured by the trypan-blue exclusion test. These results indicate that the in vivo blocking effect of glucocorticoids on basophil accumulation during LPR is mediated in part by direct action to inhibit the migration of basophils.

Reversibility of the allergen-provoked late asthmatic response by an inhaled beta 2-adrenoceptor agonist

There is uncertainty about the relative contributions of bronchial smooth muscle contraction, mucosal oedema and mucus plugging to airflow obstruction in the allergen-induced late asthmatic response (LAR). We systematically studied the ability of the inhaled beta 2-agonist salbutamol to reverse the LAR in eight subjects after allergen bronchoprovocation. Salbutamol reversed the LAR by restoring FEV1 to a level similar to the initial value measured at the same time of day (18.00 h) on the previous evening. For the eight subjects studied, this initial FEV1 value, measured after abstaining from beta-agonists for 8 h, was a mean +/- SEM 90.7 +/- 5.6% of predicted, which suggests further bronchodilation may have been possible at this time. We then studied six of the eight subjects in an identical protocol with saline challenge substituted for allergen bronchoprovocation to answer the question whether further bronchodilation was possible at that time after salbutamol in the absence of an LAR. After salbutamol on the allergen challenge day the FEV1 for the six subjects was 84.1 +/- 7.0% of predicted, compared with 94.0 +/- 3.7% of predicted at the same point on the saline challenge day (P < 0.05). We conclude that, although the LAR may be effectively reversed by beta 2-agonists, there is evidence for some residual airway narrowing, presumably related to mucosal oedema, exudate and mucus plugging.

The effect of immunotherapy on the cutaneous late phase response to antigen

BACKGROUND

This study used the skin chamber model to evaluate prospectively the effect of immunotherapy (IT) on the cutaneous early and late phase response (LPR) to epicutaneous antigen challenge.

METHODS

Nine subjects with allergic rhinitis were studied at three time points: before starting IT, after 3 months of IT, and after 6 months of IT. Skin chamber histamine content was measured hourly for 12 hours, and cell counts performed hourly during hours 6 to 12. An intradermal skin test was placed, and the reaction was measured hourly for 12 hours. Skin biopsy specimens were obtained 8 hours after intradermal placement and evaluated for cellular infiltrate and major basic protein deposition. Serum antigen-specific IgG and IgE levels were measured at each time point to confirm physiologic effect of IT.

RESULTS

Six months of IT significantly (p < 0.05) decreased both early and LPR skin test reactivity and skin chamber histamine for hours 1 to 3, 4 to 6, and 9 to 12. Skin chamber LPR cellular influx decreased significantly (p < 0.05) for neutrophils only. Decrease in LPR histamine after 6 months of IT was significantly correlated with both decrease in mononuclear cells (R2 = 0.817, p = 0.002) and decrease in neutrophils (R2 = 0.813, p = 0.009). Also significantly correlated were decrease in LPR skin test reactivity, with percent change in skin chamber mononuclear cells (R2 = 0.800, p = 0.009) and decrease in early skin test reactivity (R2 = 0.675, p = 0.01). Biopsy specimens showed no consistent change in either dermal cellular infiltrate or deposition of major basic protein.

CONCLUSION

IT significantly attenuates cutaneous histamine release and skin test reactivity and is accompanied by a decrease in skin chamber LPR neutrophil influx without significantly altering the dermal infiltrate at 8 hours.

[Asthma: an inflammatory disease]

Asthma is a bronchial disease, which is often allergic. Progress in the knowledge of its physiopathology allowed the demonstration of the local bronchial inflammatory process. The arguments supporting this new approach are experimental, clinical and therapeutical. This new approach is confirmed by the real therapeutical revolution, bronchial anti-inflammatory treatment based on inhaled corticosteroids. Furthermore, this approach was clearly synthetized by a new definition of asthma, which resulted from a recent international consensus.

Bronchial provocation with cat allergen: correlation between the individual IgE-CRIE pattern and the occurrence of a late allergic reaction

Twenty-one mild asthmatic patients allergic to cat dander underwent a bronchial provocation test (BPT) with a cat extract. An early allergic response (EAR) was observed in all 21 patients and a late allergic response (LAR) in 8/21 patients. In the EAR, the patients with subsequent LAR had a greater fall in FEV1. Their baseline FEV1, and total dose of inhaled allergen were not significantly different from patients who did not develop a LAR, but their serum specific IgE level was higher. Crossed immunoelectrophoresis (CIE) of the same cat extract showed that it contained eight different proteins. An IgE-CRIE was obtained from all 21 patients, using radiolabelled anti-IgE and autoradiography. Radiolabelled standards allowed a semiquantitative scoring of the radiostaining. The CRIE pattern of the eight patients with LAR showed a higher score of radiostaining and a greater number of proteins bound to IgE. The two major allergen cat albumin and Fel dI bound equally to IgE of patients with and without LAR whereas another protein (antigen No. 7) bound to IgE of 100% of patients with LAR but of only 38% of patients without LAR. These data suggest that the pattern of the IgE response to specific proteins of a cat extract may be related to the occurrence of LAR after BPT with this allergen.

The late-phase reaction: role of IgE, its receptor and cytokines

Late phase IgE-mediated reactions (LPR) likely play a major role in the pathogenesis of chronic allergic diseases. Although a number of cellular and humoral alterations in LPR sites have been described recently, the pathogenesis of the LPR is still unclear. LPR follow IgE-mediated but not opiate-induced mast-cell activation suggesting different patterns of mast cell mediator release and/or additional effects of the antigen-IgE interaction. Granulocyte accumulation in developing LPR is accompanied by altered expression of adhesion molecules on local vascular endothelium. Lymphocytes and the cytokines they produce play an important role in developing and perpetuating LPR. These findings point to the likely complex pathogenesis of LPR with implications for the therapy of allergic diseases.

Regular inhaled salbutamol and airway responsiveness to allergen

Regular inhaled beta 2 agonist causes tolerance to the acute protective effect of beta 2 agonist against bronchoconstriction induced by chemical stimuli such as AMP, histamine, and methacholine. We examined a more clinically relevant stimulus, inhaled allergen, in a double-blind, cross-over, random-order trial in 13 mild atopic asthmatics, who had not used beta 2 agonist for at least 4 weeks. We compared regular inhaled salbutamol (200 micrograms four times daily for 2 weeks) with placebo (2 weeks) for effects on bronchodilator response, baseline methacholine, and allergen airway responsiveness, and on the acute protective effect of salbutamol against both stimuli. Baseline forced expiratory volume in 1 s (FEV1), bronchodilator response, and methacholine responsiveness were the same during both treatment periods. After regular salbutamol, the allergen PC20 (provocation concentration producing a 20% FEV1 decrease) fell by 0.91 (SD 0.66) (p = 0.0009) doubling doses, and the protective effects of salbutamol on methacholine and allergen were both significantly reduced (p = 0.026 and 0.025, respectively). Taking into account the reduced baseline allergen PC20, the post-salbutamol allergen PC20 was almost 2 doubling doses (1.94 [1.43], p < 0.01) lower during salbutamol treatment. Thus, 2 weeks of regular inhaled salbutamol increased airway responsiveness to allergen but not to methacholine, and caused tolerance to the protective effect of salbutamol on bronchoconstriction induced by both stimuli. These effects of inhaled beta 2 agonist provide further evidence to support detrimental effects of their regular use.

Absence of specific IgE antibodies in allergic contact sensitivity to formaldehyde

Immunologic reactions are customarily divided into two broad categories, cell-mediated and antibody-mediated. An interplay between these two pathogenetic principles is indicated by reactions such as cutaneous basophil hypersensitivity, late-phase reaction, and cutaneous lesions indistinguishable from regular allergic contact dermatitis lesions after sensitization with IgE antibodies against certain haptens. In the present study, 23 patients with a history of a positive epicutaneous test to formaldehyde participated. On retest, 15 showed a positive reaction. Eight patients were Phadiatop positive, indicating an atopic diathesis, and eight had a history of or ongoing atopic dermatitis. On RAST test, only two, nonatopic patients had specific IgE antibodies to formaldehyde. In the cellular infiltrates of biopsies from epicutaneous test sites, cells reactive with monoclonal antibodies against IgE were found in positive and negative formalin tests, both in atopics and nonatopics, as well as in control biopsies from nonlesional skin. Double immunofluorescence staining experiments showed that IgE occurred on Langerhans' cells. The proportion of IgE-positive cells correlated to the level of serum IgE, but not to atopy. These cells were also found both in the epidermis and in the dermis in nonatopic patients. ICAM-1 occurred on keratinocytes in all patient groups. This study does not support the hypothesis that specific IgE antibodies are active in the pathogenesis of contact sensitivity to formaldehyde either in atopic or in nonatopic patients.

Basophil mediator release in atopic dermatitis

Basophils have been implicated as a source of histamine and pro-inflammatory eicosanoids in atopic dermatitis. However, mechanisms regulating basophil mediator release are not understood. An H3 receptor involved in the control of histamine synthesis and release has been identified in nervous tissue. In this study we have investigated 1) release of histamine, leukotriene C4, and prostaglandin D2 from anti-immunoglobulin E (IgE)-stimulated basophils of adults with atopic dermatitis and unaffected individuals and 2) specific H3 receptor-dependent basophil mediator release, using an H3 receptor agonist and antagonist. Basophil-rich leukocyte fractions were prepared by dextran sedimentation of venous blood from 19 patients with atopic dermatitis (five male, 14 female, mean age 30.6 years, range 19-59 years) and 15 unaffected individuals (five male, 10 female, mean age 27.6 years, range 19-50 years). Anti-IgE (0.78-78.0 micrograms/ml) stimulation of basophils induced a concentration-dependent release of histamine and leukotriene C4, but not prostaglandin D2. Histamine release was maximally induced by 7.8 micrograms/ml anti-IgE with no significant (Mann-Whitney U test) difference between atopic basophils (n = 17; 43.65 +/- 4.16% mean +/- SEM) and normal basophils (n = 13; 52.23 +/- 4.39%). LTC4 release was maximal from atopic basophils incubated with 2.6 micrograms/ml anti-IgE (n = 5; 0.99 +/- 0.29 pg/10(6) cells) and from normal basophils incubated with 0.78 microgram/ml anti-IgE (n = 5; 25.38 +/- 5.79 pg/10(6) cells). Anti-IgE-stimulated release of leukotriene C4 from atopic basophils was significantly less than from normal basophils at all concentrations (p < 0.05). Basophils were co-incubated with anti-IgE (2.6 and 7.8 micrograms/ml) and either the H3 receptor agonist, (R)alpha-methylhistamine (10(-8) and 10(-7) M), or the H3 receptor antagonist thioperamide (10(-6) and 10(-5) M). Neither drug modulated anti-IgE-induced release of histamine (atopics, n = 10; normals, n = 8). These results indicate 1) that basophils from adults with atopic dermatitis release the same amount of histamine as, but less leukotriene C4 than, basophils of unaffected adults and 2) that H3 receptors are not involved in anti-IgE release of histamine from basophils. These data do not support a role for increased basophil release of histamine as a mediator in the itch and erythema of atopic dermatitis in adults.

The involvement of eosinophils in the patch test reaction to aeroallergens in atopic dermatitis: its relevance for the pathogenesis of atopic dermatitis

Atopic dermatitis (AD) is considered a T-cell mediated disease. Activated T-cells, mainly of the CD4-subtype, are abundantly present in lesional AD skin. Although not many intact eosinophils are present, deposits of eosinophil derived major-basic-protein (MBP) and eosinophil-cationic-protein (ECP) suggest eosinophil involvement. After patch testing AD patients with aeroallergens, an eczematous reaction develops after 24-48 hr at the site of application. This patch test reaction shows macroscopic resemblance to lesional AD skin and does not take place in normal individuals, asthma and allergic rhinitis patients. Lymphocytes together with eosinophils infiltrate into the dermis 2-6 hr after allergen application. Twenty-four to forty-eight hours after patch testing, eosinophils are in an activated state since they release ECP (being EG2-positive). At this point in time eosinophils have also infiltrated the epidermis. Here they are EG2-negative. Forty-eight to seventy-two hours after patch testing the eczematous reaction decreases. This coincides with disappearance of eosinophils from both the dermis and the epidermis; then, a dendritic staining pattern can be observed in the epidermis with anti-eosinophil peroxidase. Thus, eosinophils infiltrate the dermis and epidermis after patch testing AD patients with aeroallergens and release part of their granular constituents. Recent in vitro investigations revealed that eosinophils from the circulation of AD patients react more powerfully in in vitro test systems such as chemiluminescence, chemotaxis and endothelial adherence and transmigration. It is very likely that this activated (= primed) state is caused by the influence of lymphocyte-derived cytokines like IL-3, IL-5 and GM-CSF, since activated lymphocytes in the circulation (and tissue) may release these cytokines. The primed state of the eosinophils may facilitate tissue infiltration. The subsequent activation of eosinophils within the tissue leading to mediator release and the function of these mediators need to be further elucidated. The close similarity between the cellular events after a patch test reaction to aeroallergens in AD patients and those present in lesional AD skin suggests that the patch test reaction may be a helpful in vivo model to study the pathogenesis of AD. The prominent involvement of lymphocytes and eosinophils in this reaction also suggests some similarity with late phase reactions (LPR) observed in the skin after intracutaneous allergen challenge.

Increases in activated T lymphocytes, eosinophils, and cytokine mRNA expression for interleukin-5 and granulocyte/macrophage colony-stimulating factor in bronchial biopsies after allergen inhalation challenge in atopic asthmatics

Immunohistology and in situ hybridization were used to evaluate the presence, activation status, and cytokine mRNA profile of cells in the bronchial mucosa during human allergen-induced asthma. Fifteen atopic asthmatic subjects underwent inhalation challenge with allergen and with allergen diluent, performed in random order separated by an interval of at least 3 wk. Bronchial biopsies were obtained 24 h after challenge. Immunostaining revealed increases in the numbers of secreting eosinophils (EG2+; P < 0.05) and in interleukin-2 receptor (IL-2R)-positive cells (CD25+; P < 0.01) after allergen compared with diluent challenge. No differences were observed in the numbers of total leukocytes (CD45+), T lymphocytes (CD3+, CD4+, and CD8+), elastase-positive neutrophils, macrophages (CD68+), or mast cell subtypes (MCT+ or MCTC+). In situ hybridization revealed significant increases in the numbers of cells expressing mRNA for IL-5 (P < 0.02) and granulocyte/macrophage colony-stimulating factor (P < 0.01) after allergen compared with diluent challenge. A significant inverse relationship was observed between the number of cells expressing mRNA for IL-4 and for interferon-gamma (r = -0.75, P < 0.02). The results support the view that cytokines possibly from activated T lymphocytes may contribute to local eosinophil accumulation during allergen-induced asthma.

Allergic inflammation

A greater understanding of the basic mechanisms of allergic inflammation is pertinent to the development of new treatments. Previous studies have focused on the role of mediators of hypersensitivity and effector cells, including mast cells and eosinophils. Recent evidence suggests that IgE-dependent activation and tissue eosinophilia are under the local regulation of distinct cytokines. Originally described as products from T lymphocytes, these peptide messengers are produced by alternative cells, including mast cells, eosinophils and the respiratory epithelium. In vitro studies in murine models and using cloned human T lymphocytes indicate the preferential production of "Th2-type" cytokines, including interleukin-4 (IL-4) and IL-5. This review considers the evidence from in vivo studies in humans that "Th2-type" cytokines have a primary role in orchestrating both IgE-dependent events and local tissue eosinophilia. Novel therapeutic approaches might include a broad strategy directed against T lymphocytes, including the use of immunosuppressive agents or anti CD4 antibodies or more precise targeting of IL-4 and/or IL-5.

Recent advances in the pathogenesis of atopic dermatitis

Atopic dermatitis (AD) is an inflammatory skin disorder affecting 5%-10% of children. Although basic mechanisms remain largely speculative, recent studies on the pathogenesis have elucidated new insights, pointing to the importance of food and inhalant allergens. The pathogenesis of AD can be more easily explained by the model of late skin reaction occurring after mast cell activation. The present report highlights some of the more recent developments in the mechanisms of AD which can be important in understanding and treating this troublesome disease.

Inflammatory mechanisms in the passive cutaneous anaphylactic reaction in the rabbit: evidence that novel mediators are involved

1. We have examined the mechanisms of local oedema formation in the passive cutaneous anaphylactic (PCA) reaction in the rabbit. 2. IgE-containing antiserum was injected i.d. and allowed to sensitize skin sites for periods up to 240 h. Antigen (bovine gamma globulin) was injected i.d. or i.v. and local oedema formation assessed by the accumulation of i.v. injected 125I-labelled rabbit serum albumin. Potential inhibitors were mixed with antigen prior to i.d. injection or were administered i.v. 3. Maximum oedema formation was observed when a sensitization period of 48-72 h was used. Oedema formation in the PCA reaction was of short duration with a t 1/2 of approximately 15 min. No evidence of late oedema formation (up to 6 h) was found. 4. Local oedema formation in the PCA was reduced by indomethacin suggesting that vasodilator, oedema-potentiating prostaglandins were released. However, it was likely that other vasodilators were also generated. 5. Antihistamines were poor inhibitors of oedema formation as were PAF antagonists, a 5-lipoxygenase inhibitor, a kallikrein inhibitor, a bradykinin antagonist and anti-C5a antibody. 6. Local oedema formation in the PCA was partially reduced by neutrophil depletion and colchicine suggesting that neutrophil-dependent mediators were involved. 7. Exudate fluid from anaphylactic reactions in the rabbit peritoneal cavity contained permeability-increasing activity when injected into rabbit skin. This activity is now being characterized. 8. A vasodilator prostaglandin appears to be released in the rabbit PCA reaction but none of the established permeability-increasing mediators appears to be involved. Thus, there may be novel inflammatory mediators generated in this reaction which may have relevance for human allergic skin diseases.

Combination of patch test and IgE for dust mite antigens differentiates 130 patients with atopic dermatitis into four groups

BACKGROUND

Patients with atopic dermatitis sometimes have positive responses to patch testing (PT) with dust mite antigens, which is believed to correlate with the elevated levels of specific IgE for those antigens.

OBJECTIVE

The purpose of this study is to identify the correlation between the PT and serum IgE concerning the mite antigens.

METHODS

We studied 130 patients with atopic dermatitis by the PT reaction and the serum level of specific IgE for Dermatophagoides pteronyssinus antigens.

RESULTS

Fifty-one of the 130 patients assessed as PT-positive had either high (32 of 130 patients; 24.6%) or low or no (19 of 130 patients; 14.6%) levels of mite-specific IgE; there was a significant difference between the groups with elevated and low IgE. Similarly, a total of 79 PT-negative patients also showed an elevated or low mite-specific IgE (42 of 130 patients [32.3%] or 37 of 130 patients [28.5%], respectively). It was noted that clinical morphologic findings were peculiar to three of the four groups; however, the patients who were PT-negative with a low IgE (37 of 130 patients) showed no particular clinical lesions.

CONCLUSION

Comparing the results from our 130 patients, there was no correlation between the serum IgE level and the PT reaction for dust mite antigens. Conversely, the results of PT and mite-specific IgE could be used to divide these patients into four distinct groups, each with its own particular clinical morphology, suggesting the heterogeneity of this disease.