Interleukin-8 secretion in patients with allergic rhinitis after an allergen challenge: interleukin-8 is not the main chemotactic factor present in nasal lavages.

BACKGROUND: Interleukin-8 (IL-8) is a chemotactic cytokine for neutrophils and primed eosinophils. In allergic rhinitis, allergen exposure triggers leucocyte recruitment. OBJECTIVE: We evaluated in this study IL-8 secretion and the neutrophil chemotactic activity in nasal lavages collected after a nasal allergen challenge. Moreover, the participation of IL-8 in the neutrophil chemotactic activity was quantified. METHODS: Four healthy subjects and 19 patients with allergic rhinitis were exposed to a nasal allergen challenge. As a control, saline challenge was performed in four patients with allergic rhinitis. Concentration of IL-8 was measured by ELISA in nasal lavages collected before and after challenge. Neutrophil chemotactic assay was developed using a 48-well chemotaxis microassembly. RESULTS: After allergen challenge, the healthy subjects, the four patients receiving saline and one patient exposed to allergen did not respond; seven patients presented a single early reaction and 11 patients a dual response. For healthy subjects and the four patients exposed to saline, the level of IL-8 did not increase after challenge in comparison with that at baseline. After allergen challenge, two peaks of IL-8 release were observed for patients with allergic rhinitis during the early (30 min to 1 h 30 min) and the late periods (3 h 30 min to 9 h 30 min), however the difference was not significant for the early period. During the late period, a significant increase in IL-8 concentrations was detected for the patients developing a dual response, whereas the difference was not significant for those presenting only an early reaction. The neutrophil chemotactic activity of nasal lavages from patients with allergic rhinitis collected during the early and the late reactions (17 +/- 2.1 and 23.3 +/- 2.8 neutrophils per high power field (hpf), respectively) was significantly higher than the activity of lavage fluid collected at baseline (9.2 +/- 1.8 neutrophils per hpf). Nevertheless, the addition of a neutralizing anti-IL-8 antibody inhibited weakly the chemotactic activity of lavage fluid from rhinitic patients collected during the early or the late periods (18 and 11% of inhibition) (P = NS). CONCLUSION: These data show that allergen challenge increased significantly the secretion of IL-8 for the patients with allergic rhinitis. However, neutralization of IL-8 in nasal lavages by a specific antibody revealed that the role of this chemokine in granulocyte infiltrate was limited, suggesting that IL-8 acts in connection with other chemotactic factors in this recruitment.

Allergen-stimulated T lymphocytes from allergic patients induce vascular cell adhesion molecule-1 (VCAM-1) expression and IL-6 production by endothelial cells.

Adhesion of inflammatory cells to endothelium is a critical step for their transvascular migration to inflammatory sites. To evaluate the relationship between T lymphocytes (TL) and vascular endothelium, supernatants from allergen-stimulated TL obtained from patients sensitive to Dermatophagoides pteronyssinus (Dpt) versus healthy subjects were added to endothelial cell (EC) cultures. TL were stimulated by autologous-activated antigen-presenting cells (APC) previously fixed in paraformaldehyde to prevent monokine secretion. Two parameters were measured: the expression of adhesion molecule and the production of IL-6. Related allergen-stimulated TL supernatants from allergic patients induced an increase of VCAM-1 and intercellular adhesion molecule-1 (ICAM-1) expression when supernatants of the control groups (TL exposed to an unrelated allergen or not stimulated or TL obtained from healthy subjects) did not. E-selectin expression was not modulated whatever the supernatant added to EC culture. IL-6 production by EC was significantly enhanced after activation with related allergen-stimulated TL supernatants from allergics compared with control supernatants. Induction of VCAM-1 expression was inhibited by adding neutralizing antibodies against IL-4, whereas IL-6 production and ICAM-1 expression were inhibited by anti-interferon-gamma (IFN-gamma) antibodies. Enhanced production of IL-4 and IFN-gamma was detected in related allergen-stimulated TL supernatants from allergic subjects compared with the different supernatants. These data suggest that allergen-specific TL present in the peripheral blood of allergic patients are of Th1 and Th2 subtypes. Their stimulation in allergic patients may lead to the activation of endothelial cells and thereby participate in leucocyte recruitment towards the inflammatory site.

Abnormal IgG4 antibody response to aeroallergens in allergic patients.

Various studies have suggested the involvement of immunoglobulin G4 (IgG4) antibodies (Ab) in the physiopathology of allergic disorders. Recently, an abnormal IgG4 Ab production in response to immunization has been reported in some atopic patients. Thus, in order to evidence in allergic patients, a potential abnormal IgG4 Ab response to aeroallergens following natural exposure, we compared, in 34 patients sensitive to Dermatophagoides pteronyssinus and in 16 healthy subjects, the IgG4 Ab response to D. pteronyssinus, grass pollen and cat dander, using a solid-phase radioimmunoassay. Since some patients were also sensitive to grass pollen and/or to cat dander, we analyzed, in all patients, the IgG4 Ab responses both towards the allergen(s) they were sensitive to (sensitizing allergen) or not (unrelated allergen). The results showed that 90% of the patients produced levels of antisensitizing allergen(s) IgG4 Ab significantly higher than the controls; this IgG4 Ab response was correlated with the corresponding specific IgE Ab level. In addition, among these patients, around 40% presented high levels of IgG4 Ab to the unrelated allergen(s). Thus, in allergic patients, while specific IgE Ab define the nature of the sensitizing allergen, the presence of IgG4 Ab directed against various allergens seems in relation with an abnormal isotype regulation associated with atopic disorders.

Interleukin-6 and interleukin-1 alpha production is associated with antigen-induced late nasal response.

BACKGROUND: Cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 alpha, IL-6 and granulocyte macrophage-colony stimulating factor (GM-CSF) are able to potentiate allergic inflammation and seem to be implicated in the development of the late allergic reaction. METHODS: To study the time course of cytokine production, sequential lavages were performed after nasal allergen challenge. Thirteen patients with allergic rhinitis and four healthy subjects were exposed to grass pollen (n = 6 and n = 2, respectively) or dust mite allergen (n = 7 and n = 2, respectively). RESULTS: Among the patients with allergic rhinitis, a single early response (single responders) developed in four, eight exhibited a dual response (dual responders) and one patient as well as the four healthy subjects did not respond. In addition to the measurement of IL-1 alpha, IL-6, TNF-alpha and GM-CSF concentrations by ELISA, the release of histamine, tryptase, and eosinophil cationic protein was also evaluated by radioimmunoassay performed on nasal lavage fluids. Concerning mediator levels in nasal lavage fluid, neither histamine release nor cytokine elevation were noted in healthy subjects. As previously described, histamine, tryptase and eosinophil cationic protein were released in single and dual responders. Concerning cytokines, TNF-alpha was undetectable in the majority of nasal lavages and an increase in GM-CSF concentration was occasionally observed whatever the type of response. In contrast, an increase in IL-1 alpha and IL-6 levels was observed for dual responders during the early period (12.6 +/- 3 and 9.2 +/- 2 pg/ml, respectively; p < 0.01 in both cases) and at a higher level during the late period (14.5 +/- 4, p not significant and 16.7 +/- 8 pg/ml, respectively; p < 0.01) when compared with baseline values (7.2 +/- 2.2 and 2 +/- 0.7 pg/ml, respectively). For single responders IL-1 alpha and IL-6 secretion was detected mainly during the early period. CONCLUSION: These data suggest a role for IL-1 alpha in the induction and perennisation of the inflammatory reaction in allergic rhinitis, whereas the role of IL-6 remains to be investigated.