[Show abstract][Hide abstract] 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.
Full-text · Article · Jan 2008 · Journal of Anatomy
[Show abstract][Hide abstract] ABSTRACT: With the exception of Agnatha, fish possess the functional equivalent of the thymus gland found in higher vertebrates. As in other vertebrates, this gland originates from the pharyngeal pouches and ontogenically is the first lymphoid organ to be infiltrated with lymphoid cells. Histology of the structure may differ from one species to another but the cellular component is basically similar. The (paired) gland is surrounded by an epithelial capsule. Within the gland a framework of reticulo-epithelial cells supports the lymphocytes. The age-related involution process, which characterizes the thymus of higher vertebrates, does not necessarily occur in fish. Nevertheless, thymus growth and function may be modulated by those factors that induce its involution such as aging, season, sexual maturity, and stress. The major role played by the thymus in the immune response of higher vertebrates is presumed to occur in fish. Thymus-derived cell dependent immune reactions have been demonstrated in fish. The cells that mediate these functions are designated as T-like cells. So far, cell surface markers equivalent to those of mammalian T lymphocytes have not been characterized. The T lymphocyte specificities are supposed to be acquired within or via the thymic microenvironment. Unfortunately, there is limited data concerned with the cytological and physiological basis of the maturation of thymus-derived cells. Direct involvement of the fish thymus in defense mechanisms has not been investigated extensively. The gland appears to be weakly protected because of its superficial location and is easily exposed to pathogens. Neoplasia is the main pathologic condition reported in the thymus of fish, with little else having been published regarding thymic pathology.
No preview · Article · Jan 1992 · Annual Review of Fish Diseases
[Show abstract][Hide abstract] ABSTRACT: The rainbow trout thymus is a paired organ, organized in 3 adjacent zones. The gland lying on a thick connective tissue layer, is covered by a thin epithelial capsule. Cellular components of thymus are essentially the thymocytes and the epithelial cells. Thymocytes occur mainly in the inner and outer zones but neither cortex nor medulla are clearly delimited. Septa represent a typical epithelial structure associated with thymocytes and blood vessels. Thymus is well vascularized and electron microscopy demonstrates a characteristic relationship between vascular system and lymphoid tissue.
No preview · Article · Feb 1983 · Developmental & Comparative Immunology
[Show abstract][Hide abstract] ABSTRACT: Cellular populations were studied in lymphoid organs of rainbow trout. Kidney appeared to be the most important organ by the number of cells harvested. A high percentage of peroxidase positive cells was measured in kidney, spleen and blood. The use of cortisone and rabbit anti-thymocyte serum showed differences in ratio of sensitive cells from different organs. In fish treated with steroids, cell depletion was verified in each organ but histologic lesions were observed only in thymus. Rabbit anti-thymocyte serum was cytotoxic for the quasi-totality of thymocytes while it destroyed only a part of kidney, spleen and blood cells. No correlations could be made between steroid sensitive cells and anti-thymocyte serum sensitive cells.
No preview · Article · Feb 1982 · Developmental & Comparative Immunology