Mucosa-associated lymphoid tissues (MALT) play a critical role as inductive sites for the initiation of antigen-specific protective immunity against pathogens penetrating the mucus membranes. Nasopharynx-associated lymphoid tissue (NALT), situated at the bottom of the rodent nasal cavity, is thought to be an important site for the induction of antigen-specific immune response to inhaled antigens. In addition, we have recently shown that tear duct-associated lymphoid tissue (TALT), present in the murine tear duct bridging the ocular and nasal cavities, is involved in the induction and regulation of both nasal and ocular immunity. Interestingly, cellular requirements for the organogenesis of NALT and TALT are quite different from those of other MALT (e.g. Peyer's patches; PPs) and peripheral lymphoid tissues. Moreover, mucosal imprinting molecules of NALT and TALT inducer cells are totally independent of currently known chemokines and adhesion molecules in PPs and lymph nodes, such as the CXCR5-CXCL13,alpha4beta1 integrin-vascular cell adhesion molecule-1 (VCAM1), and CCR9-CCL25 axes. NALT and TALT lymphocytes are also independent of these tissue-specific migration molecules.
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