Regulation of tolerance in the respiratory tract: TIM-1, hygiene, and the environment.

In this chapter we will discuss the regulation of immune responses in the respiratory mucosal system, rather than in the gastrointestinal mucosal system. However, because the lung and gastrointestinal tracts derive developmentally from a common endoderm, immune mechanisms in the respiratory and gastrointestinal tracts are likely to be very similar. Therefore, concepts that are learned about the respiratory tract are likely to benefit the understanding of tolerance in the gastrointestinal tract. We will discuss the regulation of immune responses in asthma, the role of respiratory tolerance, mediated by dendritic cells and regulatory T cells in the lung. In addition, we will discuss a genetic approach to better understand respiratory tolerance and the discovery of the TIM gene family, which regulates the development of Th2 responses, asthma, and tolerance. Finally, we will discuss the association in humans of TIM-1 and atopy, and the relationship between TIM1, hygiene, and the environment.