Nasal-associated lymphoid tissue (NALT) orchestrates immune responses to Ags in the upper respiratory tract. Unlike other lymphoid organs, NALT develops independently of lymphotoxin-α (LTα). However, the structure and function of NALT are impaired in Ltα-/- mice, suggesting a link between LTα and chemokine expression. In this study we show that the expression of CXCL13, CCL19, CCL21, and CCL20 is impaired in the NALT of Ltα-/- mice. We also show that the NALT of Cxcl13-/- and plt/plt mice exhibits some, but not all, of the structural and functional defects observed in the NALT of Ltα-/- mice. Like the NALT of Ltα-/- mice, the NALT in Cxcl13-/- mice lacks follicular dendritic cells, BP3+ stromal cells, and ERTR7+ lymphoreticular cells. However, unlike the NALT of Ltα-/- mice, the NALT of Cxcl13-/- mice has peripheral node addressin + high endothelial venules (HEVs). In contrast, the NALT plt/plt mice is nearly normal, with follicular dendritic cells, BP3+ stromal cells, ERTR7+ lymphoreticular cells, and peripheral node addressin+ HEVs. Functionally, germinal center formation and switching to IgA are defective in the NALT Ltα-/- and Cxcl13-/- mice. In contrast, CD8 T cell responses to influenza are impaired in Ltα-/- mice and plt/plt mice. Finally, the B and T cell defects in the NALT of Ltα-/- mice lead to delayed clearance of influenza from the nasal mucosa. Thus, the B and T cell defects in the NALT of Ltα-/- mice can be attributed to the impaired expression of CXCL13 and CCL19/CCL21, respectively, whereas impaired HEV development is directly due to the loss of LTα. Copyright © 2005 by The American Association of Immunologists, Inc.