• Lung function FEV1 [ Time Frame: days ] [ Designated as safety issue: Yes ]
  
• Suppression of monocyte activation and alveolar macrophage activation by dexamethasone ex-vivo [ Time Frame: Days ] [ Designated as safety issue: No ]
  
• Effect of corticosteroids on release of cytokines from macrophages [ Time Frame: Once ] [ Designated as safety issue: No ]
  

• Exhaled NO [ Time Frame: Days ] [ Designated as safety issue: No ]
  
• Biopsy eosinophils [ Time Frame: Once ] [ Designated as safety issue: No ]
  
• Sputum eosinophils [ Time Frame: Once ] [ Designated as safety issue: No ]
  

Inclusion Criteria:

The final diagnosis of severe asthma will be made according to the screening steps we have set up. The definition will require the presence of one or both major criteria (treatment with continuous or near continuous oral corticosteroids and/or requirement for treatment with high dose inhaled steroids) and two minor criteria.

Patients who do not fit the criteria of severe asthma will not be entered into the study.

Age 18-60; both sexes.

For the investigation of fiberoptic bronchoscopy, other additional inclusion criteria will be imposed:

1. Post-bronchodilator FEV1 greater than 40% on the day of the bronchoscopy
2. No evidence of an exacerbation of asthma within the past 4 weeks.
3. Ability to cooperate with procedures
4. Ability to give consent
5. Current smokers, and ex-smokers with greater than 10 pack years history of smoking.

Exclusion criteria

Pregnancy or unreliable contraceptive measures in child-bearing woman. he bronchoscopist has determined the subject is clinically appropriate for bronchoscopy

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Exclusion Criteria:

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