ABSTRACT
Thymic epithelial reticular cells together with lymphocytes constitute the thymic parenchyma. Morphologically they are characterized by the stellate aspect forming a cytoreticulum, a large and vesicular nucleus, a tonofilament-rich cytoplasm, and abundance of desmosomes. Besides the role of providing a structural support for lymphocytes, epithelial reticular cells are responsible for the secretion of thymic hormones which promote lymphocyte proliferation and maturation. Clinical evidence is now appearing suggesting such thymic hormones' use as therapeutic agents against immunodeficiency diseases and cancer.
Subject(s)
Thymus Gland/cytology , Chromatin/ultrastructure , Cytoplasmic Granules/ultrastructure , Cytoskeleton/ultrastructure , Desmosomes/ultrastructure , Epithelial Cells , Epithelium/metabolism , Epithelium/physiology , Epithelium/ultrastructure , Euchromatin , Humans , Thymus Gland/metabolism , Thymus Gland/physiology , Thymus Hormones/metabolismABSTRACT
Thymic involution is normally a slow process, but can be accelerated by some pathological or experimental conditions. In this paper it is suggested that cold may be an agent to artificially induce thymic involution in the golden hamster. Animals kept at low temperature for 2 months exhibited a high degree of thymus atrophy, histologically characterized by an intense lymphocyte depletion with a concomitant loss of a clearly-distinguished cortico-medullary arrangement. In these animals, thymic white fat was largely replaced by brown adipose tissue. The role of low temperature as a direct or indirect agent to induce thymic involution is discussed.
Subject(s)
Cold Temperature , Thymus Gland/anatomy & histology , Adipose Tissue/anatomy & histology , Animals , Cricetinae , Male , Mesocricetus , Thymus Gland/physiologySubject(s)
Antigens, Helminth/immunology , Parabiosis , Schistosoma mansoni/immunology , Schistosomiasis/immunology , Animals , Granuloma/parasitology , Intestines/pathology , Liver/pathology , Liver Diseases, Parasitic/immunology , Macrophage Migration-Inhibitory Factors , Male , Mice , Mice, Inbred C3H , Spleen/pathology , T-Lymphocytes/immunologyABSTRACT
The phenomenon of autofluorescence is reported in the thymus of rabbits; besides reticular epithelial cells, Hassall's bodies also emit autofluorescence. The staining of thymic corpuscle by fluorescein isothiocyanate is also described. This staining is important not only because FITC is commonly used in immunofluorescence and may lead to misinterpretations due to false-positive results, but also for it permits a good precision in the observation of the relationship between Hassall's bodies and reticular epithelial cells. Some hypothesis are set up to explain the autofluorescence, and the fluorochromization of Hassall's bodies by acid fluorochromes.
