Grass pollen immunotherapy inhibits seasonal increases in basophils and eosinophils in the nasal epithelium.

BACKGROUND: Symptoms of allergic rhinitis are accompanied by infiltration of the nasal mucosa with inflammatory cells, predominantly eosinophils and metachromatic cells (basophils and mast cells). Specific immunotherapy (IT) reduces mucosal eosinophilia and numbers of metachromatic cells in the epithelium. A specific marker distinguishing basophils from mast cells was recently developed. OBJECTIVES: The basophil-specific monoclonal antibody 2D7 was used to determine the influence of subcutaneous IT on numbers of nasal mucosal basophils compared with the effects of IT on neutrophils, eosinophils and mast cells. METHOD: During a randomized, placebo-controlled trial of grass pollen IT in 44 adults with severe summer hay fever, nasal biopsies were taken at baseline, out of the pollen season, and at the peak of the pollen season following 2 years treatment. Biopsies were processed for immunohistochemistry for basophils (2D7+), mast cells (AA1+), eosinophils (MBP+) and neutrophils (neutrophil elastase+). RESULTS: In placebo-treated (PL) patients there were significant seasonal increases in basophils (P < 0.01), mast cells (P < 0.05) and eosinophils (P = 0.002) in the nasal submucosa. In IT-treated patients significant increases in 2D7+ cells (P < 0.01) and eosinophils (P = 0.01) but not AA1+ cells (P = 0.9) were observed. These differences were significant between groups for eosinophils (P < 0.05). In the epithelium there were seasonal increases in AA1+ cells and eosinophils in both groups (PL: P < 0.01, IT: P < 0.05 for both). The between-group difference was significant for eosinophils (P = 0.05). Basophils were observed in the epithelium of six out of 17 in the placebo group and one out of 20 in the IT group (P = 0.03). Neutrophil numbers remained constant in both epithelium and submucosa. CONCLUSION: Successful grass pollen immunotherapy was associated with inhibition of seasonal increases in basophils and eosinophils, but not mast cells or neutrophils within the nasal epithelium. Immunotherapy may act, at least in part, by reducing seasonal recruitment of basophils and eosinophils into the epithelium.

Immunohistochemical detection of human basophils in late-phase skin reactions.

BACKGROUND: Human basophils are difficult to detect with classic histochemical stains at sites of allergic inflammation. The 2D7 anti-basophil monoclonal antibody was used to identify basophils in skin during the late-phase response to a cutaneous allergen challenge. METHODS: The 2D7 monoclonal antibody was used on protease-digested sections of skin biopsy specimens obtained 6 and 24 hours after an allergen or buffer challenge. The skin chamber technique was used to compare buffer- and allergen-challenged sites at 6 hours, and intradermal injection of allergen was used to compare allergen-challenged sites at 6 and 24 hours. RESULTS: Dramatic increases in the numbers of 2D7+ cells and in tissue staining by 2D7 were observed 6 hours after allergen challenge compared with buffer challenge. Histamine levels in skin chamber fluid varied with 2D7+ cell concentrations. By 24 hours, 2D7+ cells and tissue staining appeared to diminish but were still detectable in the allergen-challenged sites. Basophils localized primarily in and around blood vessels, whereas mast cells remained mostly in the superficial dermis. Mast cells were 2D7- in both the allergen- and buffer-challenged skin. Metachromatic staining of 2D7+ basophils with toluidine blue was absent in these tissue sections. CONCLUSIONS: The 2D7 monoclonal antibody provides a more sensitive and precise marker than histochemical staining for human basophil involvement during the late-phase response to an allergen challenge. Basophil infiltration was observed at 6 hours only after allergen challenge and persisted at similar levels by 24 hours.

The immediate and late allergic response to segmental bronchopulmonary provocation in asthma.

The response to antigen is an important factor in the development of airway inflammation. Segmental bronchoprovocation (SBP) with antigen and subsequent bronchoalveolar lavage (BAL) have provided valuable insight into the mechanisms of allergic inflammation. To determine the features of allergic airway response in asthma, 19 subjects with mild asthma underwent antigen SBP in a dose-dependent manner. The amount of antigen used in SBP was 0 (saline), and 1, 5, or 20% of the antigen dose required to drop the FEV1 by 20% (APD20). BAL was done at 5 min and 48 h after SBP. BAL histamine levels increased modestly 5 min after antigen SBP. At 48 h, there was a marked increase in eosinophils and IL-5 concentration even in airway segments where the release of histamine was small. Moreover, eosinophils correlated with IL-5 levels at 48 h (r = 0.63; p < 0.001), but not with BAL histamine concentrations at 5 min. GM-CSF levels did not increase after antigen SBP and did not correlate with eosinophils. These observations indicate that asthmatic subjects can develop a dose-dependent response to antigen SBP that is characterized by a modest increase in histamine immediately after antigen exposure, and marked eosinophilia, which appears proportionately greater than the histamine response and relatively greater than what is seen in allergic nonasthmatic subjects. This feature might be important to the eventual development of airway inflammation in asthma.

A common cold virus, rhinovirus 16, potentiates airway inflammation after segmental antigen bronchoprovocation in allergic subjects.

Many patients with asthma have increased wheezing with colds. We hypothesized that rhinovirus colds might increase asthma by augmenting airway allergic responses (histamine release and eosinophil influx) after antigen challenge. Seven allergic rhinitis patients and five normal volunteers were infected with rhinovirus type 16 (RV16) and evaluated by segmental bronchoprovocation and bronchoalveolar lavage. Segmental challenge with saline and antigen was performed 1 mo before infection, during the acute infection, and 1 mo after infection. Lavage was performed immediately and 48 h after antigen challenge. Data were analyzed by two-way analysis of variance, and a P value of < or = 0.05 was considered to be significant. All volunteers inoculated with RV16 developed an acute respiratory infection. BAL fluid obtained from allergic rhinitis subjects during the acute viral infection, and 1 mo after infection, showed the following significant RV16-associated changes after antigen challenge: (a) an enhanced release of histamine immediately after local antigen challenge; (b) persistent histamine leak 48 h afterwards; and (c) a greater recruitment of eosinophils to the airway 48 h after challenge. These changes were not seen in non-allergic volunteers infected with RV16 and challenged with antigen, nor in allergic volunteers repetitively challenged with antigen but not infected with RV16, nor in RV16 infected allergic volunteers sham challenged with saline. We conclude that rhinovirus upper respiratory infection significantly augments immediate and late allergic responses in the airways of allergic individuals after local antigen challenge. These data suggest that one mechanism of increased asthma during a cold is an accentuation of allergic responses in the airway which may then contribute to bronchial inflammation.

Release of histamine and tryptase during continuous and interrupted cutaneous challenge with allergen in humans.

To help in understanding the patterns of in vivo mediator release in human allergic skin reactions, we have used a skin chamber model to challenge the denuded bases of skin blisters of 11 sensitive subjects with pollen antigens (Ags) and codeine (C), a mast cell degranulator. Challenges were performed either (1) continuously for 6 hours or (2) in an intermittent fashion that is, Ag or C for the first hour, buffer for the next 4 hours, and then Ag or C during the sixth hour. Fluids in the overlying chamber were assayed for levels of the mast cell components, histamine and tryptase. There was peak release of both histamine and tryptase during the first hour of Ag incubation (89 +/- 11 ng/ml and 1428 +/- 260 ng/ml, respectively). At continuous Ag-challenge sites, there was a plateau of histamine levels (8.0 to 9.5 ng/ml) during the next 4 hours, whereas tryptase levels decreased progressively to baseline levels. Challenge of continuous Ag-incubation sites with C, a mast cell activator, led to another peak release of both histamine and tryptase. At interrupted Ag-challenge sites, histamine levels decreased abruptly, and tryptase levels decreased progressively after the first hour. Rechallenge of such sites with Ag during the sixth hour induced a peak release of histamine but no increase in tryptase levels. Continuous challenge with C for up to 5 hours in other sites induced an initial peak histamine release without a subsequent plateau. However, such a plateau of histamine (but not tryptase) release occurred after an initial C challenge if Ag was subsequently incubated in a continuous fashion.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of histamine and tryptase in vivo after prolonged cutaneous challenge with allergen in humans.

The patterns of in vivo release of histamine and tryptase were determined during prolonged Ag incubation in atopic individuals, using skin chambers placed over denuded skin blister sites. However, the patterns of histamine and tryptase release over a period of up to 9 h of Ag exposure were different. Whereas rates of release of both histamine and tryptase peaked within 1 h in an Ag dose-response fashion, that of tryptase decreased progressively thereafter and was not different from buffer challenge sites from the 5th to 9th h at all concentrations of Ag tested. The rate of histamine release reached a plateau after 2 h and remained at a constant low level throughout the 3rd to 9th h of Ag incubation. Rechallenge of the sites continuously exposed to Ag with a different second Ag at the 6th h resulted in a second peak of release of both histamine and tryptase. This persistence of in vivo histamine but not tryptase release during the later time points of the cutaneous allergic response differs from what has been demonstrated in vitro with dispersed mast cells. Whether this reflects basophil participation at these time points or an as yet undetermined mechanism for release of histamine but not tryptase by mast cells is not known. These novel patterns of mediator release after prolonged Ag exposure in vivo may have clinical relevance to allergic diseases during which atopic subjects are exposed to Ag over several hours to days.