Tissue targeting of T cells by DCs and microenvironments

With the rapid growth in our understanding of tissue-selective lymphocyte trafficking, the complexity of this phenomenon has begun to unravel. It is now becoming clear that effector and memory T cells are endowed with a topographical memory of the site of primary antigen encounter. During activation of naive T cells in secondary lymphoid tissues, a combinatorial access code of adhesion molecules and chemokine receptors is generated that targets T cells to the corresponding peripheral tissues. Recently, an intrinsic ability of dendritic cells to induce tissue-selective T cells was demonstrated. Furthermore, an important role for local tissue microenvironments has been shown. However, the crucial factors responsible for the programming of distinct patterns of T-cell migration have yet to be identified. Here, we attempt to correlate the present knowledge with our view of the mechanisms for this instructive process.