The relationship of sputum eosinophilia and sputum cell generation of IL-5.

BACKGROUND: Eosinophil recruitment to the airway after antigen challenge is regulated by many factors, including airway cell generation of cytokines. OBJECTIVES: The purpose of this study was to determine the relationship between sputum cell generation of IL-5 and the appearance of eosinophils in the sputum after antigen challenge. METHODS: Sputum samples from 11 allergic subjects were collected before and again 4 and 24 hours after antigen challenge. In 6 of these subjects, induced sputum samples were also obtained 48 hours and 7 days after challenge. Sputum leukocyte differential and cell counts and eosinophil-derived neurotoxin levels were determined. Sputum cells were then cultured with PHA (10 microg/mL) to stimulate IL-5 and IFN-gamma, which were measured in culture supernatants. RESULTS: An increase in sputum eosinophils and eosinophil-derived neurotoxin levels was detected at 4 hours after antigen challenge, with peak values at 24 hours. In contrast, significant increases in ex vivo generation of IL-5 by sputum cells was not seen until 24 hours after challenge. At 24 hours, PHA-induced IL-5 correlated with airspace eosinophil values (r (s) = 0.78, P <.01). In addition, the ratio of IFN-gamma/IL-5 decreased at 24 hours (P <.05) and had an inverse correlation with sputum eosinophils (r (s)= -0.68, P <.05). CONCLUSION: Although eosinophils are increased in the airway lumen as early as 4 hours, the ex vivo generation of IL-5 by sputum cells is first noted in samples obtained 24 hours after antigen challenge. This suggests that the early (4 hours) recruitment of eosinophils to the airway lumen may be regulated by factors other than IL-5 or that mucosal cells (rather than airspace cells) contribute to the IL-5 generation at this time point. Furthermore, IL-5 generation by airspace cells may be more responsible for either eosinophil recruitment or retention at later time points.

Late allergic airway response to segmental bronchopulmonary provocation in allergic subjects is related to peripheral blood basophil histamine release.

BACKGROUND: Basophil histamine release has been found to correlate with the presence and severity of allergic disease. However, it remains to be established whether airway response to antigen is related to basophil involvement and its release of histamine. OBJECTIVE: The purpose of this study was to investigate whether the intensity of airway response to an inhaled antigen challenge in allergic subjects is related to IgE-dependent peripheral blood basophil histamine release. METHODS: The response to segmental bronchoprovocation with antigen was examined in 34 subjects with allergic rhinitis. Bronchoalveolar lavage samples were obtained 5 minutes (immediate response) and 48 hours (late response) after allergen challenge. Peripheral blood maximal basophil histamine release (MBHR) in response to in vitro antigen stimulation was determined in each subject before segmental bronchoprovocation. RESULTS: Bronchoalveolar lavage samples obtained during immediate response showed an increase in histamine, whereas the late response was noted for a marked enhancement in airway cells, particularly eosinophils. Interestingly, a significant correlation (r = 0.73, p < 0.0001, Spearman Rank test) was noted between MBHR and intensity of bronchoalveolar lavage eosinophilia at 48 hours. Furthermore, subjects with high (> or = 20%) MBHR had significantly higher total cells and eosinophils in bronchoalveolar lavage fluid 48 hours after antigen segmental bronchoprovocation when compared with subjects with low (< 20%) MBHR. CONCLUSION: Our data suggest that the intensity of airway eosinophilia in response to antigen challenge is correlated with the magnitude of basophil mediator release in allergic subjects.

The effect of T-cell depletion on enhanced basophil histamine release after in vitro incubation with live influenza A virus.

A number of mechanisms participate in virus-induced asthma. Previously, we described enhanced basophil histamine release (HR) during an experimentally induced rhinovirus infection and after in vitro incubation of peripheral blood mononuclear cells (PBMC) with influenza virus. This study extends our previous observations and examines the effect of influenza A virus on basophil leukotriene C4 (LTC4) release as well as the effect of T-cell depletion on virus-enhanced basophil HR. PBMC were isolated from ragweed-allergic subjects and incubated with live influenza A virus or control medium (allantoic fluid). After incubation with influenza A, ragweed antigen (AgE) stimulated LTC4 and HR were enhanced (P less than 0.05). To further define the role of T cells in virus-enhanced basophil secretion, PBMC were isolated and divided into two aliquots. In one aliquot, T cells were removed by magnetic bead separation of mouse monoclonal anti-CD3-coated lymphocytes. T-cell-depleted and nontreated PBMC suspensions were incubated with influenza A or control medium, collected, and challenged with AgE to release histamine. Basophil HR was enhanced in the virus-treated group of PBMC that had not undergone T-cell depletion. In contrast, virus incubation did not enhance HR in the T-cell-depleted fraction. Finally, preliminary analysis of the supernate from virus-treated leukocytes indicates the presence of interferon-gamma. These findings suggest that T cells, and their cytokine products, play an integral role in the process by which viruses enhance basophil HR.