The development and structure of mouse nasal-associated lymphoid tissue: an immuno- and enzyme-histochemical study

This study deals with the structure and development of Nasal-Associated Lymphoid Tissue (NALT) in the mouse. NALT is present in the nasal cavity on both sides at the entrance of the pharyngeal duct. The lymphocytes are organized in B- and T-cell areas covered by an epithelium in which M-cells are present. Immuno- and enzyme-histochemistry showed that NALT is already present at birth. Before birth, accumulations of Ia-positive dendritic cells and a few B lymphocytes were the first signs of the formation of NALT. These cell accumulations occurred just under the epithelium in the nasal floor. At birth, NALT could be distinguished as an accumulation of mainly B lymphocytes and Ia positive dendritic cells in a network of reticulum cells. The covering simple epithelium showed crypt-like invaginations. B- and T-cell areas appeared at seven days after birth. High endothelial venules (HEV) were observed from day 7 onward; from day 14 they could be stained with the HEV-specific monoclonal antibody MECA-325. Ia-positive dendritic cells increased in number during ontogeny. They occurred both in NALT and between the covering epithelial cells. Also, some epithelial cells expressed the Ia-antigen. The number of acid phosphatase positive macrophages increased steadily during ontogeny. The cells were mainly observed in the connective tissue surrounding NALT and just under the epithelium. They displayed antigenic determinants characteristic of macrophages (Moma-1, Moma-2). The structure and development of NALT are compared with those of other parts of the mucosa-associated lymphoid tissue.