Background: We have shown that interleukin-5 (IL-5) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are present in sputum from patients experiencing acute asthma attacks, by eosinophil survival assay. The viability of guinea-pig eosinophils was significantly increased in the presence of such sputum extracts after 3 days' culture, and it was inhibited by the addition of anti-IL-5 and anti-GM-CSF antibodies. However, the contribution of IL-5 to the increase in eosinophil viability was less than expected from the values of IL-5 measured by enzyme-linked immunosorbent assay (ELISA). Therefore, we speculated that something in sputum inhibited the function of IL-5.
Objective: Transforming growth factor-beta (TGF-beta) was the only cytokine we tested that inhibited the prolongation of survival of guinea-pig eosinophils induced by IL-5. The objective of this study is to detect TGF-beta in the same sputum.
Methods: Guinea-pig eosinophils were cultured with or without anti-TGF-beta antibody in the presence of sputum extracts, and the eosinophil viability was counted after 3 days. Measurement of TGF-beta 1 in sputum was performed by ELISA.
Results: Eosinophil viabilities with and without anti-TGF-beta antibody were 79.7 +/- 2.9% and 69.0 +/- 2.7%, respectively, and the difference between them was statistically significant (P < 0.05, n = 9). The concentration of TGF-beta 1 in the sputum was 21.7 +/- 3.3 ng/mL (n = 9).
Conclusion: These observations suggest that TGF-beta is present in sputum from patients with bronchial asthma.