Lympho-myeloid és hemopoietikus szervek fejlődésbiológiája: embryomanipuláció = Development of the lympho-myeloid and hemopoietic organs: embryo manipulation

A pályázat fő célja volt a bursai szekréciós dendritikus (BSDC), a follikuláris dendritikus (FDC) és a Langerhans sejtek (LC) eredetének és differenciálódásának vizsgálata. BSDC véreredetű sejtek terminális differenciálódásuk függ az anyai eredetű antigénektől. A A fertőző bursa betegséget okozó vírus először a BSDC-ben mutatható ki, bizonyítva, hogy a BSDC az elsőrendű célsejtje a vírusoknak. 5-fluorouracil okozta heterophil depléció eliminálja a vírusfertőzés okozta mortalitást és a súlyos klinikai tüneteket és emeli a BSDC-k számát. A heterophil granulocyták a BSDC-vel együtt jelentős szerepet játszanak a fertőző bursa betegség (Gumboro) klinikai tüneteinek kialakulásában. Az LC haptén kezelés hatására kivándorolnak az epidermisből és subcután előforduló lymphoid nodulusokban jelennek meg. A lép ellipszoidhoz-asszociált sejtei (EAC) hemopoietikus eredetűek. Az EAC az egyetlen olyan phagocyta tulajdonságú sejt, amely internalizálja a β-galactozidázt ez pedig elindítja az EAC migrációját a T dependens területek (PALS) és a csíracentrumok felé. Monoklonális antitest (E5G12) felismeri az EAC-t és az FDC-t is, mely lehetőséget adott kettős festésre (β-gal hisztokémia és E5G12 immuncytokémia). A kettős festés egyértelmű bizonyítékot szolgáltatott arra, hogy a lép csíracentrumok FDC-jei EAC eredetűek. A csirke embryok vérében perifériás vér fibrocyták jelen vannak, melyek hozzájárulnak a lép organogenesiséhez. Ez a munka vezetett az a lép ellipszoidok körüli Schweigger-Seidel hüvely tokjának felfedezéséhez. A csirkék gastrointestinalis traktusában oesophagealis és pylorus tonsillak kerültek leírásra. | The origin and differentiation of bursal secretory dendritic (BSDC), follicular dendritic (FDC), and Langerhans cells (LC) have been studied. BSDC are blood-borne hemopoietic cells, and their differentiation depends on maternal antigen. The antibody against infectious bursal disease viruses indicates that the BSDC are primary targets of the IBDV. Depletion of heterophil granulocytes by 5-fluorouracil results in elimination of major clinical symptoms and mortality, increase the number of BSDC. After hapten treatment the Langerhans cells migrate out of the epidermis and appear in the subcutaneous lymph nodules. The splenic ellipsoid-associated cells (EAC) are blood-borne cells. They exclusively internalize the β-galactosidase, which initiate their migration to the T dependent region (PALS) and germinal centers. Monoclonal antibody E5G12, recognizes EAC and splenic FDC. Double-staining (β-galactosidase histochemistry) and E5G12 immunocytochemistry provided clearcut evidence that the EAC were precursors of FDC. No double labeled cells were found in the GC of the GALT, which might indicate that the origin of splenic and GALT FDC have had different origin. The presence of the avian peripheral blood fibrocytes in the circulation contribute to the splenic extracellular matrix, which forms arround the ellipsoid a discontinuous sheath, what we called "capsule of Schweigger-Seidel sheath" (CSS). We have identified oesophageal and duodenal tonsils, which are specific for the birds

Avian coronavirus infection induces mannose-binding lectin production in dendritic cell precursors of chicken lymphoid organs

The aim of this immunocytochemical study was to compare mannose-binding lectin (MBL) production induced by avian coronavirus in the spleen and caecal tonsil (CT). One-day-old specific-pathogen-free (SPF) chickens were experimentally infected with six QX field isolates and the H120 vaccine strain. In the negative control birds, the spleen was MBL negative, while the CT showed scattered MBL-positive cells in close proximity and within the surface epithelium and germinal centre (GC)-like cell clusters. MBL was detectable in the ellipsoid-associated cells (EACs) and cell clusters in the periarterial lymphoid sheath (PALS) by 7 days post infection (dpi). In both organs, the MBL-positive cells occupy antigen-exposed areas, indicating that GC formation depends on resident precursors of dendritic cells. The majority of MBL-positive EACs express the CD83 antigen, providing evidence that coronavirus infection facilitated the maturation of dendritic cell precursors. Surprisingly, co-localisation of MBL and CD83 was not detectable in the CT. In the spleen (associated with circulation), the EACs producing MBL and expressing CD83 are a common precursor of both follicular (FDC) and interdigitating dendritic cells (IDC). In the CT (gut-associated lymphoid tissue, GALT) the precursors of FDC and IDC are MBL-producing cells and CD83-positive cells, respectively. In the CT the two separate precursors of lymphoid dendritic cells provide some ‘autonomy’ for the GALT

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 különül: keratinpozitív hálózatra és keratinnegatív területre. A keratinpozitív hálózat összeköttetésben áll a kérgi hámreticulummal, míg a keratinnegatív terület folyamatos a septumok kötőszöveti állományával. A keratinnegatív területnek, a toknak és a septumnak a támasztószövete reticularis kötőszövet. A kéregállományt a tok és a septumok reticularis kötőszövetétől folyamatos bazális membrán választja el, de a keratinnegatív területek és a keratinpozitív hálózat határánál a bazális membrán szakadozottá válik. Ez az immunhisztokémiai lelet az első, amely magyarázhatja, hogy miért nincs a velőállományában vér-thymus barrier. A keratinnegatív terület és a septumok támasztószövetének azonossága azt sugallja, hogy a sövények és a keratinnegatív területek azonos eredetűek. A thymus tokja és sövényei a cranialis ganglionlécből származnak, ezért feltételezzük, hogy a keratinnegatív terület is ganglionléc-eredetű. A velőállomány vérerei a keratinnegatív területben helyezkednek el, ezért minden, a thymusból kilépő vagy abba belépő, immunológiailag kompetens sejtnek keresztül kell mennie a keratinnegatív területen. Ez azt sugallja, hogy a keratinnegatív terület a thymus tranzitzónája. A hematoxilin-eozin festés alapján megjelenő kéreg-velő határt nem reprezentálja sejtes háttér, de a keratinpozitív hálózat és a keratinnegatív terület között húzódó határt sejtes összetétele határozza meg (epithelium-mesenchyma). Feltételezzük, hogy a keratinnegatív terület és a keratinpozitív hálózat között lévő határ a thymus valódi szövettani és funkcionális határa. Orv Hetil. 2019; 160(5): 163–171. | 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

Coronavirus infection retards the development of the cortico-medullary capillary network in the bursa of Fabricius of chicken

Coronavirus infection delays the development of the cortico-medullary (CM) capillary network which results in retarded development of bursal follicles. The smaller size of the medulla in the coronavirus-infected birds may lead to a lower number of B lymphocytes and bursal secretory dendritic cells, which negatively affects the reactivity and efficacy of the immune system. Contrary to the wild-type infectious bronchitis virus (IBV) strain, infection induced by H120 vaccine virus exerts only a moderate influence on caveolin-1 expression of the CM capillary web and on follicular development compared to the untreated controls

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

Hemangioblast commitment in the avian allantois: cellular and molecular aspects.

We recently identified the allantois as a site producing hemopoietic and endothelial cells capable of colonizing the bone marrow of an engrafted host. Here, we report a detailed investigation of some early cytological and molecular processes occurring in the allantoic bud, which are probably involved in the production of angioblasts and hemopoietic cells. We show that the allantois undergoes a program characterized by the prominent expression of several "hemangioblastic" genes in the mesoderm accompanied by other gene patterns in the associated endoderm. VEGF-R2, at least from stage HH17 onward, is expressed and is shortly followed by transcription factors GATA-2, SCL/tal-1, and GATA-1. Blood island-like structures differentiate that contain both CD45(+) cells and cells accumulating hemoglobin; these structures look exactly like blood islands in the yolk sac. This hemopoietic process takes place before the establishment of a vascular network connecting the allantois to the embryo. As far as the endoderm is concerned, GATA-3 mRNA is found in the region where allantois will differentiate before the posterior instestinal portal becomes anatomically distinct. Shortly before the bud grows out, GATA-2 was expressed in the endoderm and, at the same time, the hemangioblastic program became initiated in the mesoderm. GATA-3 is detected at least until E8 and GATA-2 until E3 the latest stage examined for this factor. Using in vitro cultures, we show that allantoic buds, dissected out before the establishment of circulation between the bud and the rest of the embryo, produced erythrocytes of the definitive lineage. Moreover, using heterospecific grafts between chick and quail embryos, we demonstrate that the allantoic vascular network develops from intrinsic progenitors. Taken together, these results extend our earlier findings about the commitment of mesoderm to the endothelial and hemopoietic lineages in the allantois. The detection of a prominent GATA-3 expression restricted to the endoderm of the preallantoic region and allantoic bud, followed by that of GATA-2, is an interesting and novel information, in the context of organ formation and endoderm specification in the emergence of hemopoietic cells