Lung dendritic cells promote lung homing by T cells in part via up-regulation of chemokine receptor CCR4.

Background-Recruitment of antigen-specific Th2 cells into the lung is critical for the development of allergic airway inflammation. Although CCR4 and CCR8 are preferentially expressed on Th2 cells and CCR4, CCR8 and CXCR3 ligands are increased in asthma, the specific relative contribution of these receptors to antigen-specific Th2 cell trafficking into the allergic lung is not known.

Th1 and Th2 effector CD4+ T cells orchestrate distinct counterregulatory biological responses. To deliver effective tissue Th1- and Th2-type responses, Th1 and Th2 cell recruitment into tissue must be differentially regulated. We show that tissue-derived STAT1 controls the trafficking of adoptively transferred, Ag-specific, wild-type Th1 cells into the lung. Trafficking of Th1 and Th2 cells is differentially regulated as STAT6, which regulates Th2 cell trafficking, had no effect on the trafficking of Th1 cells and STAT1 deficiency did not alter Th2 cell trafficking. We demonstrate that STAT1 control of Th1 cell trafficking is not mediated through T-bet. STAT1 controls the recruitment of Th1cells through the induction of CXCL9, CXCL10, CXCL11, and CXCL16, whose expression levels in the lung were markedly decreased in STAT1−/− mice. CXCL10 replacement partially restored Th1 cell trafficking in STAT1-deficient mice in vivo, and deficiency in CXCR3, the receptor for CXCL9, CXCL10, and CXCL11, impaired the trafficking of adoptively transferred Th1 cells in wild-type mice. Our work identifies that STAT1 in peripheral tissue regulates the homing of Ag-specific Th1 cells through the induction of a distinct subset of chemokines and establishes that Th1 and Th2 cell trafficking is differentially controlled in vivo by STAT1 and STAT6, respectively.