[The tonsils as MALT (mucosa-associated lymphoid tissue) of the nasal mucosa]

One of the most effective defense mechanisms of the nasal mucosa is its immune response leading to the synthesis of antibodies directed against inhaled antigens. In order to understand the immunology of the upper respiratory tract it is essential to know whether this response takes place within the mucosa itself or within regional lymphoid organs. The authors investigated cell populations involved in immune processes within the mucosa and as a model of a lymphoid organ, in the tonsil. Using a range of monoclonal cell surface markers, the authors concentrated on antigen-presenting cells, the B-cell differentiation, and T-cell subpopulations and their corresponding activation markers. The findings demonstrate that the normal mucosa has no organized lymphoid structures and few or no early, maturing, or activated B-lymphocyte stages. The antibody-producing plasma cells found within the mucosa can therefore not be regarded as locally formed. On the contrary, the palatine tonsils demonstrate a typical lymphoid structure and contain all activation and differentiation stages of B-lymphocytes from premature to plasma cells. This would suggest that the human nasal mucosa is not capable of providing a local immune response, but is dependent on lymphoid organs like the tonsil, as the regional "mucosa-associated lymphoid tissue" (MALT).