Regulation of helper T cell differentiation and recruitment in airway inflammation

CD4(+) helper T type 1 (Th1) and Th2 cells are critical mediators of inflam matory diseases. Although T cells represent only a fraction of the leukocyt es that are found in the lung during inflammation, they play a critical rol e in coordinating the immune response to infectious agents and allergens. T cells have the ability to rapidly expand in response to specific stimuli a nd to differentiate into effector cells that, through the production of sol uble factors such as cytokines and chemokines, communicate with other cells to initiate a cascade of inflammatory events. The objective of this review is to outline the cellular and molecular mechanisms involved in the genera tion and recruitment of Th1 and Th2 cells in the lung. Defining these mecha nisms should lead to improved immunopharmacological strategies for prophyla xis and therapy.