Role of lymphotoxin and homeostatic chemokines in the development and function of local lymphoid tissues in the respiratory tract.

Secondary lymphoid organs are strategically placed to recruit locally activated antigen presenting cells (APCs) as well as naïve, recirculating T and B cells. The structure of secondary lymphoid organs - separated B and T zones, populations of specialized stromal cells, high endothelial venules and lymphatic vessles - has also evolved to maximize encounters between APCs and lymphocytes and to facilitate the expansion and differentiation of antigen-stimulated T and B cells. Many of the general mechanisms that govern the development and organization of secondary lymphoid organs have been identified over the last decade. However, the specific cellular and molecular interactions involved in the development and organization of each secondary lymphoid organ are slightly different and probably reflect the cell types available at that time and location. Here we review the mechanisms involved in the development, organization and function of local lymphoid tissues in the respiratory tract, including Nasal Associated Lymphoid Tissue (NALT) and inducible Bronchus Associated Lymphoid Tissue (iBALT).