Elevated complement factor H levels in asthmatic sputa

The alternative pathway of the complement system is known to play a role in the generation of asthmatic airway inflammation, but its regulatory complement protein, factor H has not been investigated in this disease.

Our aim was to determine the local bronchial complement factor H (CFH) levels in asthma, and to investigate its relationship with complement activation, systemic CFH concentrations and clinical characteristics of patients.

Induced sputum and plasma were collected from 21 healthy and 26 asthmatic subjects, and complement factor H and SC5b-9 concentrations were assessed by ELISA. Total protein concentrations were determined by biuret-reaction based microassay system from induced sputa.

CFH was detectable in 81 % of healthy and 100 % of asthmatic subjects, while SC5b-9 exceeded the detection limit in 62 % of healthy subjects and 85 % of asthmatic patients. Sputum CFH concentrations and CFH/protein ratios were increased in samples from asthmatic patients, and correlated with loss of lung function, asthma control, severity and medication intensity, but not with plasma CFH concentrations. Sputum CFH/protein ratios were in positive correlation also with sputum eosinophilic cell counts in asthma. SC5b-9 concentrations were not higher in the asthmatic sputa, although they correlated with sputum CFH concentrations.

CFH level is elevated on asthmatic airway surface, and may be associated with uncontrolled inflammation in asthma.