Regulatory cells and the control of respiratory infection.

The role of distinct CD4+ T-cell populations in regulating the nature and strength of immune responses is well documented, and has in the past principally focused on the mutual antagonism between Th1 and Th2 cells, which secrete interferon (IFN)-gamma and interleukin (IL)-4, respectively. However, the recent identification of T cells that secrete high levels of IL-10 and/or transforming growth factor-b, but not IFN-g or IL-4, called regulatory T (Tr) cells has prompted a paradigm shift in our understanding of the regulation of immune responses following infection. In this review, we focus on the role of antigen-specific Tr cells in the lungs following infection with various respiratory pathogens and discuss the targeting of Tr in the development of new therapies for immune-mediated diseases, such as allergy.