Bovine lingual tonsil: histomorphological characteristics with special reference to the follicular dendritic cells.

In the bovine, the lingual tonsil is localized at the lingual radix. However, as the expansion of the tonsillar tissue was presumed to be much larger than the macroscopically visible part, selected specimens from the bovine tongue were examined to clarify if lymphatic tissue of the lingual tonsil was present rostral of a defined macroscopical landmark, i.e. rostral of the most caudal of the papillae vallatae. The identification of the lymphoreticular system was validated by means of the detection of reticulum cells, especially follicular dendritic cells (FDC). They characterize the tonsillar lymph nodules and distinguish them structurally from unspecific accumulations of lymphocytes. In our study, two monoclonal antibodies, i.e. CNA.42 and D46, detected bovine FDC cells in situ. 'Organized' lymphoid tissue--i.e. solitary lymph nodules and aggregations of lymph nodules, both either with or without surrounding connective tissue, and with or without crypts, but with immunopositive reactions for FDC--could be observed up to 30 mm rostral of the most caudal of the papillae vallatae. As these formations were not identified macroscopically, they shall be referred to as the disseminate part of the lingual tonsil.