Control of IL-5 production by human helper T cells as a treatment for eosinophilic inflammation: comparison of in vitro and in vivo effects between selective and nonselective cytokine synthesis inhibitors.

BACKGROUND: Helper T cells are involved in the pathophysiologic condition of asthma, so modulation of cytokine production may be effective therapy.
OBJECTIVE: We aimed to selectively control the synthesis of IL-5 by helper T cells and tested in vivo effects using a murine asthma model.
METHODS: The effect of dexamethasone, FK506, cyclosporin A, and nonactin (a macrolide compound produced by Streptomyces griseus) on cytokine production by allergen-specific T-cell clones was determined. The effect of these agents and an anti-IL-5 neutralizing antibody on airway eosinophilic inflammation was investigated in a murine asthma model.
RESULTS: Dexamethasone, FK506, and cyclosporin A suppressed the production of IL-2, IL-4, and IL-5 by human helper T cells, which shows a similar concentration-response relationship in each case. Cyclosporin A and dexamethasone inhibited airway eosinophilia in vivo. Nonactin suppressed IL-5 synthesis but not IL-2 or IL-4 synthesis, and it also significantly suppressed airway eosinophilia.
CONCLUSION: Nonactin only suppressed IL-5 synthesis and was as effective against eosinophilia as cyclosporin A and dexa-methasone, which indicates that IL-5 is a reasonable therapeutic target in allergic disorders that are accompanied by eosinophilic inflammation.