Animal models of asthma: Potential usefulness for studying health effects of inhaled particles

Asthma is now recognized to be a chronic inflammatory disease that affects the whole lung. Incidence appears to be increasing despite improved treatme nt regimens. There is substantial epidemiological evidence suggesting a rel ationship between the incidence and severity of asthma ( e. g., hospitaliza tions) and exposure to increased levels of air pollution, especially fine a nd ultrafine particulate material, in susceptible individuals. There have b een a few studies in animal models that support this concept, but additiona l animal studies to test this hypothesis are needed. However, such studies must be performed with awareness of the strengths and weaknesses of the cur rently available animal models. For studies in mice, the most commonly used animal, a broad spectrum of molecular and immunological tools is available , particularly to study the balance between Th1 and Th2 responses, and inbr ed strains may be useful for genetic dissection of susceptibility to the di sease. However, the mouse is a poor model for bronchoconstriction or locali zed immune responses that characterize the human disease. In contrast, alle rgic lung diseases in dogs and cats may more accurately model the human con dition, but fewer tools are available for characterization of the mechanism s. Finally, economic issues as well as reagent availability limit the utili ty of horses, sheep, and primates.