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 viabihty 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 Tratnsforming growth factor-β (TGF-β) 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-β in the same sputum. Methods Guinea-pig eosinophils were cultured with or without anti-TGF-β antibody in the presence of sputum extracts, and the eosinophil viability was counted after 3 days. Measurement of TGF-βl in sputum was performed by ELISA. Results Eosinophil viabilities with and without anti-TGF-β 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-β1 in the sputum was 21.7 ± 3.3 ng/mL (n = 9).
Conclusion These observations suggest that TGF-β is present in sputum from patients with bronchial asthma.