Summary
The ultrastructure of the micro-environment of the fully functional rat thymus was studied. The thymus consists of two discrete compartments, viz., an epithelial and a mesenchymal compartment. Thymus fibroblasts/fibrocytes, mast cells and granulocytes, are restricted to the mesenchymal compartment. The thymocyte maturation process seems to occur in the epithelial compartment in a network of reticular epithelial cells. The cortex is finely meshed and filled with proliferating thymocytes and some scattered macrophages. Moreover, in the medulla vacuolated epithelial cells form part of a loosely meshed reticulum which is filled with thymocytes and interdigitating cells (IDCs). IDCs frequently contain Birbeck granules and appear to be phagocytic. Together with macrophages, they probably enter the thymus, predominantly in the cortico-medullary region, and cross the separating wall between the two compartments. Some functional aspects of the non-lymphoid cells and in particular the IDCs, which form the micro-environment of the thymus, are discussed with respect to T-cell development.
Similar content being viewed by others
References
Bearman RM, Levine GD, Bensch KG (1978) The ultrastructure of the normal human thymus: a study of 36 cases. Anat Rec 190:755–782
Beelen RHJ, Fluitsma DM, Hoefsmit ECM (1980) Milky spots in the omentum. Cellular compositon of milky spots and fine structures of milky spot macrophages and reticulum cells. J Reticuloendothel Soc 28:585
Beller DI, Unanue ER (1978) Thymic macrophages modulate one stage of T-cell differentiation in vitro. J Immunol 121:1861–1864
Beller DI, Unanue ER (1980) Ia antigens and antigen-presenting function of thymic macrophages. J Immunol 124:1433–1441
Birbeck MS, Breathnach AS, Everall JD (1961) An electron microscopic study of basal melanocytes and high-level clear cells (Langerhans cells) in vitiligo. J Invest Derm 37:51–64
Chapman WL, Allen JR (1971) The fine structure of the thymus of the fetal and neonatal monkey (Macaco mulatta). Z Zellforsch 114:220–233
Clark SL (1963) The thymus in mice of strain 129/J, studied with the electron microscope. Am J Anat 112:1–33
Furth, R van, Cohn ZA, Hirsch JG, Humphrey JH, Spector WG, Langevoort HL (1972) The mononuclear phagocyte system: a new classification of macrophages, monocytes and their precursor cells. Bull WHO 46:845
Gaudecker, B von, Müller-Hermelink HK (1980) Ontogeny and organization of the stationary non-lymphoid cells in the human thymus. Cell Tissue Res 207:287–306
Haelst U van (1967) Light and electron microscopic study of the normal and pathological thymus of the rat. I. The normal thymus. Z Zellforsch 77:534–553
Hoefsmit ECM, Kamperdijk EWA, Balfour BM (1980) Reticulum cells and macrophages in the immune response. In: Furth R van (ed) Mononuclear phagocytes. Martinus Nijhoff Publishers, The Hague, pp 1809
Hoshino T (1963) Electron microscopic studies of the epithelial reticular cells of the mouse thymus. Z Zellforsch 59:513–529
Hwang WS, Ho TY, Luk SC, Simon GT (1974) Ultrastructure of the rat thymus. Lab Invest 31:473–487
Kaiserling E (1977) Strukturen und Reaktionsformen des normalen Lymphknotens. In: Seifert G (ed) Non-Hodgkin Lymphome. Gustav Fischer Verlag, Stuttgart New York, pp 10
Kamperdijk EWA, Raaymakers EM, Leeuw JHS de, Hoefsmit ECM (1978) Lymph node macrophages and reticulum cells in the immune response. I. The primary response to paratyphoid vaccine. Cell Tissue Res 192:1–23
Klug H, Mager B (1979) Ultrastructure and function of interdigitating cells in the guinea pig thymus. Acta Morphol Acad Sci Hung 27:11–19
Kobayashi M, Hoshino T (1976) Occurrence of Birbeck granules in the macrophage of mouse lymph nodes. J Electr Microsc 25:83–90
Mandel T (1968) Ultrastructure of epithelial cells in the cortex of guinea pig thymus. Z Zellforsch 92:159–168
Meyler FJ (1960) Over de mechanische activiteit van het ε-isoleerde, volgens Langendorff doorstroomde, zoogdierhart. Acad Thesis, Amsterdam, The Netherlands
Mosier DE, Pierce CW (1972) Functional maturation of thymic lymphocyte populations in vitro. J Exp Med 136:1484–1500
Owen JT (1972) The origin and development of lymphocyte populations. In: Ontogeny of acquired immunity. A Ciba Found Symp, North Holland, Elsevier, p 35
Pease DC (1964) Histological techniques of electron microscopy, 2nd ed, Acad Press, New York London, pp 234
Raviola E, Karnovsky MJ (1972) Evidence for a blood-thymus barrier using electron-opaque tracers. J Exp Med 136:466–498
Reynolds ES (1963) The use of lead citrate at high pH as an electron-opaque stain in electron microscopy. J Cell Biol 17:208–212
Rhee HJ van der, Burgh-de Winter CPM van der, Daems WTh (1979) The differentiation of monocytes into macrophages, epithelial cells and multinucleated giant cells in subcutaneous granulomas. Cell Tissue Res 197:355–378
Rouse RV, Ewijk W van, Jones PP, Weissman IL (1979) Expression of MHC antigens by mouse thymic dendritic cells. J Immunol 122:2508–2515
Stingl G, Katz SI, Shevach EM, Wolff-Schreiner EC, Green I (1978) Detection of Ia antigens on Langerhans cells in guinea pig skin. J Immunol 120:570–578
Törö I, Oláh I (1966) Electron microscopic study of guinea pig thymus. Acta Morphol Acad Sci Hung 14:275–290
Veerman AJP (1974) On the interdigitating cells in the thymus-dependent area of the rat spleen: a relation between the mononuclear phagocyte system and T-lymphocytes. Cell Tissue Res 148:247–257
Veerman AJP, Hoefsmit ECM, Boeré H (1974) Perfusion fixation using a cushioning chamber coupled to a peristaltic pump. Stain Technol 49:111–112
Veldman JE (1970) Histophysiology and electron microscopy of the immune response. Acad Thesis, Groningen, The Netherlands
Wekerle H, Cohen I, Feldman M (1973) Thymus reticulum cell cultures confer T cell properties on spleen cells from thymus deprived animals. Eur J Immunol 3:745
Wolff K (1972) The Langerhans cell. Curr Probl Dermatol 4:79–145
Zinkernagel RM, Callahan GN, Althage A, Cooper S, Klein PA, Klein J (1978a) On the thymus in the differentiation of “H-2 self-recognition” by T-cells: evidence for dual recognition? J Exp Med 147:882
Zinkernagel RM, Callahan GN, Althage A, Cooper S, Streilein JW, Klein J (1978b) The lymphoreticular system in triggering virus plus self-specific cytotoxic T-cells: evidence for T help. J Exp Med 147:897–911
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Duijvestijn, A.M., Hoefsmit, E.C.M. Ultrastructure of the rat thymus: The micro-environment of T-lymphocyte maturation. Cell Tissue Res. 218, 279–292 (1981). https://doi.org/10.1007/BF00210344
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00210344