Anatomy and cytology of the thymus in juvenile Australian lungfish, Neoceratodus forsteri

Abstract

The anatomy, histology and ultrastructure of the thymus of a dipnoan, the Australian lungfish, Neoceratodus forsteri , was studied by light and transmission electron microscopy. The thymic tissue showed clear demarcation into a cortex and medulla with ample vascularization. Large cells including foamy and giant multinucleated cells with periodic acid Schiff/Alcian blue positive staining properties were localized mainly in the medulla. The major cellular components were epithelial cells and lymphoid cells. The epithelial cells were classified by location and ultrastructure into six sub-populations: capsular cells, cortical and medullary reticular cells, perivascular endothelial cells, intermediate cells, nurse-like cells and Hassall-like corpuscles. Myoid cells were found mainly in the cortico-medullary boundary and medulla. Macrophages and secretory-like cells were also present. These findings will provide a base of knowledge about the cellular immune system of lungfish.

Morphological and immunohistochemical characterisation of the thymus in juvenile turbot (Psetta maxima, L.)

“…In our work, thymic nurselike cells were visualised in the inner zone of the organ as was earlier stated in O. mykiss (Flaño et al 1996). In other fish species such as Cyprinus carpio (Romano et al 1999b), N. forsteri (Mohammad et al 2007) and D. puntazzo (Romano et al 1999a), thymic nurse-like cells were identified at the boundary of the outer and inner zones, whereas in Siniperca chuatsi this cell type was located in the outer zone of the thymus (Xie et al 2006). While thymic nurse cells were immunoreactive to anti-CYT antibodies in fish (Flaño et al 1996) as in mammals (Pezzano et al 2001), no immunoreaction of this cell type to anti-CYT antibody was observed in this study.…”

“…In some fish species such as Neoceratodus forsteri (Mohammad et al 2007), S. sanguineus (Gorgollon 1983) and D. puntazo (Romano et al 1999a), analogous structures to the Hassall's corpuscles of mammals have been reported. However, their existence seems to be controversial (Chilmonczyk 1992), since in other species such as O. mykiss ) and R. rutilus (Zapata 1981) Hassall's corpuscles were not observed.…”

“…To be precise, thymocytes are not strictly included within the cytoplasm of thymic nurse cells. Thymocytes are surrounded by cytoplasmic projections of a thymic nurse cell and thus both cell types are apposing their plasma membranes (Flaño et al 1996;Xie et al 2006;Mohammad et al 2007). At least in mammals, this cell association is related to positive or negative selection of thymocytes depending on their TCR binding affinity to numerous self-peptide-MHC complexes (Pezzano et al 2001).…”

“…The morphology and cellular composition of fish thymus vary greatly, especially their epithelial components (Gorgollon 1983;Castillo et al 1990;Chilmonczyk 1992;Romano et al 1999a;Xie et al 2006;Mohammad et al 2007). Reticulo-epithelial cells (RECs) have been described and classified mainly by means of transmission electron microscopy.…”

The first finding of Hassall's corpuscles in the thymi of cultured sturgeons

“…They were described in lungfish (Mohammad et al 2007), in teleosts (Bowden et al 2005) and in mammals (Furukawa et al 2012).…”