Morphological characterisation of the vestibular folds as larynx-associated lymphoid tissue in the adult bactrian camel (Camelus bactrianus)

Ultrastructure and composition of the lymphoid follicles (LF) found in the vestibular folds (FVC) of the bactrian camel were examined by immunohistochemistry, scanning and transmission electron microscopy. Immunohistochemical examination revealed that CD³ and CD²⁰ positive lymphocytes, CD⁶⁸ positive macrophages were distributed in the different areas of follicles at different ratio. The positive follicular dendritic cells (FDC) were only found in germinal centres. Electron microscopy revealed that non ciliated microvillous cells with irregular microvilli, displaying features characteristic of microvillous cells (M cells), were present in the follicle-associated epithelium (FAE) that covered the lymphoid follicles. The bright germinal centre (GC) contained lymphoblasts, follicular dendritic cells, apoptotic lymphocytes and macrophages. The distribution of high endothelial venules (HEVs) was observed in the parafollicular area (PFA). The morphological findings of LF suggested that the presence of lymphoid follicles and inflammatory cells in the FVC was common, and was part of the normal histological morphology of larynx in the camel. As an active component of the larynx associated lymphoid tissue (LALT) in the camel, the FVC were inductive sites for the common mucosal immune system as well as important components in larynx defense.