Interleukin-1 beta: a possible mediator of lung inflammation and airway hyperreactivity.

Interleukin-1 (IL-1), a peptide released from monocytes/macrophages, plays an important role in the inflammatory and immune responses. Airway hyperreactivity and the underlying airway inflammation are common features in asthma pathology. We investigated and characterized the inflammatory alterations induced within the guinea-pig respiratory system by IL-1 beta. Injection of IL-1 beta (1-6 micrograms/animal) into the pleural space resulted in a dose-dependent inflammatory response, as shown by the formation of pleural exudate and leucocyte recruitment. A threshold dose of IL-1 beta (1 micrograms/animal) markedly potentiated the inflammatory reaction triggered by the classical proinflammatory agent croton oil, underlining the amplifying role of IL-1 beta in the inflammatory events. The inflammatory process induced by intrapleural injection of IL-1 beta (6 micrograms/animal) was associated with the development of a hyperreactive phenomenon which involved both the peripheral and large airways. In fact, increased contractile activity of histamine was evident in the tracheas and parenchymal strips isolated from guinea-pigs exposed to IL-1 beta. These results provide evidence for a possible role of IL-1 beta in the genesis of airway inflammation and bronchial hyperreactivity.