5 research outputs found
A thymus szerkezete a huszonegyedik század elején = Structure of the thymus at the beginning of the 21th century
Absztrakt:
A thymus klasszikus hisztológiai tulajdonságai: a kéreg- és velőállomány, a
Hassall-testek és a mirigyekre jellemző lebenyezettség. Az anti-páncitokeratin
festése azt mutatja, hogy a kérgi és velőhámsejtek keratinmintázata különböző. A
velőállomány további kompartmentekre kĂĽlönĂĽl: keratinpozitĂv hálĂłzatra Ă©s
keratinnegatĂv terĂĽletre. A keratinpozitĂv hálĂłzat összeköttetĂ©sben áll a kĂ©rgi
hámreticulummal, mĂg a keratinnegatĂv terĂĽlet folyamatos a septumok kötĹ‘szöveti
állományával. A keratinnegatĂv terĂĽletnek, a toknak Ă©s a septumnak a
támasztószövete reticularis kötőszövet. A kéregállományt a tok és a septumok
reticularis kötőszövetétől folyamatos bazális membrán választja el, de a
keratinnegatĂv terĂĽletek Ă©s a keratinpozitĂv hálĂłzat határánál a bazális membrán
szakadozottá válik. Ez az immunhisztokémiai lelet az első, amely magyarázhatja,
hogy miĂ©rt nincs a velőállományában vĂ©r-thymus barrier. A keratinnegatĂv terĂĽlet
és a septumok támasztószövetének azonossága azt sugallja, hogy a sövények és a
keratinnegatĂv terĂĽletek azonos eredetűek. A thymus tokja Ă©s sövĂ©nyei a
cranialis ganglionlĂ©cbĹ‘l származnak, ezĂ©rt feltĂ©telezzĂĽk, hogy a keratinnegatĂv
terĂĽlet is ganglionlĂ©c-eredetű. A velőállomány vĂ©rerei a keratinnegatĂv
területben helyezkednek el, ezért minden, a thymusból kilépő vagy abba belépő,
immunolĂłgiailag kompetens sejtnek keresztĂĽl kell mennie a keratinnegatĂv
terĂĽleten. Ez azt sugallja, hogy a keratinnegatĂv terĂĽlet a thymus
tranzitzónája. A hematoxilin-eozin festés alapján megjelenő kéreg-velő határt
nem reprezentálja sejtes háttĂ©r, de a keratinpozitĂv hálĂłzat Ă©s a keratinnegatĂv
terület között húzódó határt sejtes összetétele határozza meg
(epithelium-mesenchyma). FeltĂ©telezzĂĽk, hogy a keratinnegatĂv terĂĽlet Ă©s a
keratinpozitĂv hálĂłzat között lĂ©vĹ‘ határ a thymus valĂłdi szövettani Ă©s
funkcionális határa. Orv Hetil. 2019; 160(5): 163–171.
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Abstract:
The classical histological features of the thymus are the cortex and medulla, the
Hassall’s bodies as well as the lobules. Anti-pan-cytokeratin
immunocytochemistry shows that the keratin staining pattern of the cortical and
medullary epithelial cells is different. The medulla is further
compartmentalized: it consists of keratin-positive network and keratin-negative
areas. Histology of the keratin-negative area is identical with the connective
tissue of the septae. The basal lamina is continuous at the capsule and septae,
but it becomes discontinuous at the border between the keratin-positive network
and keratin-negative area. This immunohistochemical finding is the first
histological sign, which may explain that the medulla has no blood-thymus
barrier. The supporting tissue of the keratin-negative area is identical with
that of the septae. The connective tissue of thymic capsule and septae develops
from the cranial neural crest cells, therefore we hypothesize that the
keratin-negative area has neural crest origin. Blood vessels of the thymic
medulla localize in the keratin-negative area. Every emigrating or immigrating
immunologically competent cells should enter the keratin-negative area,
therefore this area is the transit zone of the thymus. The hematoxylin-eosin
staining of the thymus shows that the thymic cortico-medullary border does not
represent cellular background. However, the border between keratin-positive
network and keratin-negative area is determined by cellular identity (epithelial
and mesenchymal tissues). Therefore, it can be assumed that the real
histological and functional border is the border between the keratin-positive
network and the keratin-negative area. Orv Hetil. 2019; 160(5): 163–171
A novel aspect of the structure of the avian thymic medulla.
We provide evidence for the compartmentalization of the avian thymic medulla and identify the avian thymic dendritic cell. The thymic anlage develops from an epithelial cord of the branchial endoderm. Branches of the cord are separated by primary septae of neural crest origin. The dilation of the primary septae produces the keratin-negative area (KNA) of the thymic medulla and fills the gaps of the keratin-positive network (KPN). Morphometric analysis indicates that the KNA takes up about half of the volume of the thymic medulla, which has reticular connective tissue, like peripheral lymphoid organs. The KNA receives blood vessels and in addition to pericytes, the myoid cells of striated muscle structure occupy this area. The myoid cells are of branchial arch or prechordal plate origin providing indirect evidence for the neural crest origin of the KNA. The marginal epithelial cells of the KPN co-express keratin and vimentin intermediate filaments, which indicate their functional peculiarity. The basal lamina of the primary septum is discontinuous on the surface of the KPN providing histological evidence for the loss of the blood-thymus barrier in the medulla. In the center of the KNA, the dendritic cells lie in close association with blood vessels, whereas the B-cells accumulate along the KPN. The organization of the KPN and KNA increases the "surface" of the so-called cortico-medullary border, thereby contributing to the efficacy of central tolerance