Distribution of S-100 positive dendritic cells in bovine pharynx, tonsils, and retropharyngeal lymph nodes

Dendritic cells (DCs) are professional antigen-presenting cells. However, the distribution of bovine DCs in the pharynx, tonsil, and retropharyngeal lymph nodes has not yet been documented. To address this issue, immunohistochemistry was conducted using S-100 protein as a marker for DCs. It was observed that S-100 positive Langerhans cells (LCs) were primarily found in the basal layer of the pharyngeal epithelium. Some DCs were found in the outer layer of the epithelium and their dendrites extended out towards the epithelial surface. In the tonsil, S-100 positive DCs were found either in follicular germinal centers or in the T-cell areas. It is worth noting that the S-100 positive DCs were not only distributed in the cortex, but also in the medulla of bovine retropharyngeal lymph nodes. The distribution patterns of bovine DCs in the pharynx, tonsil, and retropharyngeal lymph nodes have an important implication for our understanding of the interaction between pathogens and host.