Background: Increased transforming growth factor beta1 (TGF-beta1) levels have been reported in bronchoalveolar lavage fluid and bronchial biopsy specimens from asthmatic patients. However, systemic TGF-beta1 levels have not been reported in asthma.
Objective: To evaluate the levels of plasma TGF-beta1 in asthmatic patients and matched, healthy controls to determine the associations with atopic status, disease severity, and duration.
Methods: Asthmatic patients and healthy controls were recruited prospectively from a university hospital outpatient department between January 2001 and May 2002. Plasma TGF-beta1 and serum IgE levels were estimated using established methods. Patients were classified as atopic or nonatopic based on the presence or absence of serum specific IgE directed to common allergens.
Results: Of the 56 patients recruited for the study, 32 were atopic and 24 nonatopic. The median value of plasma TGF-beta1 was significantly higher in nonatopic asthmatic patients (2.5 ng/mL) compared with controls (1.5 ng/mL, P = .002) and atopic asthmatic patients (1.4 ng/mL, P = .008). The median absolute neutrophil count in the nonatopic asthmatic patients (4.0 x 10(9)/L) was significantly higher compared with atopic asthmatic patients (3.0 x 10(9)/L) and healthy controls (3.5 x 10(9)/L) (P = .01 and P = .04). There was no significant correlation between the duration or severity of asthma and plasma TGF-beta1 levels. The distribution of moderate-persistent asthma cases was similar in atopic and nonatopic groups.
Conclusion: Compared with atopic asthmatic patients and healthy controls, patients with nonatopic asthma have elevated plasma TGF-beta1 levels and leukocytosis. These data suggest that nonatopic asthmatic patients exhibit an altered inflammatory response, perhaps to a respiratory infection.