Antigen-dependent rescue of nose-associated lymphoid tissue (NALT) development independent of LTbetaR and CXCR5 signaling.

Nose-associated lymphoid tissue (NALT) in the rodent upper respiratory tract develops postnatally and is considered to be independent of several factors known to be involved in the organogenesis of LN and Peyer's patches (PP). In this study we demonstrate that at least two different pathways result in NALT development. Following NALT anlage formation the intrinsic pathway relies on a signaling cascade including those mediated through the chemokine receptor CXCR5 and the lymphotoxin beta receptor (LTbetaR). This allows for the formation of high endothelial venules and thereby the recruitment of lymphocytes into NALT. Alternatively, high endothelial venule formation and lymphocyte recruitment can be induced in the NALT anlage by environmental signals, which are independent of LT-betaR and chemokine receptor CXCR5 signaling but in part rely on CD40 ligand. Thus, our study identifies a novel mechanism that facilitates the rescue of NALT development at late stages in adult life independent of the canonical LTbetaR-CXCR5 signaling axis.