Dynamics of dendritic cell phenotype and interactions with CD4⁺ T cells in airway inflammation and tolerance

An emerging concept is that different types of dendritic cells (DCs) initiate different immune outcomes, such as tolerance vs inflammation. In this study, we have characterized the DCs from the lung draining lymph nodes of mice immunized for allergic airway inflammation or tolerance and examined their interactions with CD4⁺ T cells. The DC population derived from tolerized mice was predominantly CD11c⁺, B220⁺, Gr-1 ⁺, CD11b^-, and MHC class II^low, which resembled plasmacytoid-type DCs whereas DCs from the inflammatory condition were largely CD11c⁺, B220^-, Gr-1^-, CD11b⁺, and MHC class II^hlgh resembling myeloid-type DCs. The DCs from the tolerogenic condition were poor inducers of T cell proliferation. DCs from both conditions induced T cell IL-4 production but the T cells cultured with tolerogenic DCs were unresponsive to IL-4 as indicated by inhibition of STAT6 activation and expression of growth factor-independent 1, which has been recently shown to be important for STAT6-activated Th2 cell expansion. Our data suggest that airway tolerance vs inflammation is determined by the DC phenotype in lung draining lymph nodes.