Erythropoiesis in an avian thymus

Combined morphological and analytical studies with the EMMA-4 analytical electron microscope have enabled very early erythroid cells to be identified within the cortex of enlarging thymic lobes of Quelea quelea . These early erythroid cells have pale cytoplasm (sometimes with ferritin-like crystals present), slightly pachychromatic nuclei and have fewer cell organelles (mitochondria) than lymphocytes. Counts for iron were approximately 70% lower than counts from mature erythrocytes found free in the cortex. Iron was also recorded from some epithelial reticular cells and pyknotic nuclei; no iron was recorded from small lymphocytes (thymocytes) in the cortex. The presence of very early erythroid cells is a further indication that erythropoiesis occurs in situ in the avian thymus.

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Tracing of cells of the avian thymus through embryonic life in interspecific chimeras.

Journal of Experimental Medicine ◽

10.1084/jem.142.1.17 ◽

1975 ◽

Vol 142 (1) ◽

pp. 17-40 ◽

Cited By ~ 288

Author(s):

N M Le Douarin ◽

F V Jotereau

Keyword(s):

Stem Cells ◽

Hatching Time ◽

Branchial Arches ◽

Before And After ◽

Embryonic Life ◽

Blood Stem Cells ◽

Avian Thymus ◽

Respective Contribution ◽

Marking Technique ◽

Different Origins

Differences in the structure of the interphase nucleus between two species of birds, the Japanese quail (Coturnix coturnix japonica) and the chick (Gallus gallus) has been used to distinguish cells from different origins in interspecies combinations. This biological cell marking technique was applied to thymus histogenesis. Using various combinations between components of quail and chick thymic rudiments, the respective contribution of endodermal epithelium, mesenchyme, and blood-borne extrinsic elements to the histogenesis of thymus was analyzed. It was demonstrated that the whole lymphoid population of the thymus is derived from immigrant blood-borne stem cells which are chemically attracted by the endoderm of the 3rd and 4th pharyngeal pouch. The latter is determined to differentiate into thymic epithelial reticulum as soon as the 15-somite stage, and is able to attract blood stem cells even when transplanted in an heterotopic position such as the ventral body wall of the embryo. It was shown that the thymic mesenchyme originates from the neural crest mesectoderm which colonizes early the 3rd and 4th branchial arches. It participates in the formation of perivascular mesenchyme, but does not give rise to lymphocytes. From heterospecific transplantations of quail thymuses into chick embryo (and inversely) at various stages of development is appeared that the thymic rudiment becomes attractive for lymphoid stem cells at a precise stage of its evolution for each species. The attractivity period lasts about 24 h for the quail and 36 h for the chick. Then, the inflow of stem cells becomes very low until the end of the incubation period. At this time, a second wave of lymphocytoblasts invades the thymus and the primitive embryonic lymphoid population is completely renewed around the hatching time. Competent thymic stem cells are present in the blood before and after the period of physiological thymic attractivity. The identity of basophilic cells appearing in the thymus during its histogenesis and lymphoid stem cells has been demonstrated from the analysis of quail-chick chimeric thymuses.

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Parvalbumin and calretinin in the avian thymus

Anatomy and Embryology ◽

10.1007/bf00185943 ◽

1993 ◽

Vol 188 (4) ◽

Cited By ~ 17

Author(s):

Elisabeth Kir�ly ◽

MarcoR. Celio

Keyword(s):

Avian Thymus

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On the differentiation and origin of myoid cells in the avian thymus

Anatomy and Embryology ◽

10.1007/bf00174622 ◽

1990 ◽

Vol 181 (3) ◽

Cited By ~ 14

Author(s):

R. Seifert ◽

B. Christ

Keyword(s):

Myoid Cells ◽

Avian Thymus

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Ultrastructural studies on erythropoiesis in the avian thymus

Cell and Tissue Research ◽

10.1007/bf00237726 ◽

1979 ◽

Vol 199 (1) ◽

pp. 37-61 ◽

Cited By ~ 27

Author(s):

Marion D. Kendall ◽

Judith A. Frazier

Keyword(s):

Ultrastructural Studies ◽

Avian Thymus

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Cells expressing Ia antigens in the avian thymus.

Journal of Experimental Medicine ◽

10.1084/jem.160.6.1803 ◽

1984 ◽

Vol 160 (6) ◽

pp. 1803-1819 ◽

Cited By ~ 62

Author(s):

F P Guillemot ◽

P D Oliver ◽

B M Peault ◽

N M Le Douarin

Keyword(s):

Epithelial Cells ◽

Apparent Molecular Weight ◽

Cell Types ◽

Adherent Cells ◽

Thymic Development ◽

Cell Network ◽

Accessory Cells ◽

Ia Antigens ◽

Avian Thymus ◽

Species Specific

The various cell types expressing Ia antigens in the chick and quail thymus have been studied by means of monoclonal antibodies (mAb) prepared by using chick and quail thymic adherent cells (macrophages and dendritic cells) as immunogens. Three reagents were selected by the following criteria: (a) they react with a surface determinant carried by thymic adherent cells and bursal lymphocytes, (b) they can be used to immunoprecipitate from spleen cell membrane extracts molecular entities of an apparent molecular weight close to 55,000, which can be fractionated into monomers at approximately 30,000 mol wt in dissociating conditions. Among these three reagents, two are strictly species specific, i.e., they recognize either chick (TaPl) or quail (TaCl) Ia determinants, whereas the third, TaC2, recognizes both chick and quail Ia molecules. Chimeric thymuses in which the epithelioconnective stroma is derived from the quail thymic primordium and the whole hemopoietic cell population (lymphocytes and accessory cells) are of chick origin were constructed as previously described by our group (20). The different mAb were applied on normal (quail and chick) and chimeric thymuses. It appears that the thymus is divided into two compartments in terms of the nature of cells expressing Ia: the cortex, in which class II antigens are exclusively expressed by endodermal epithelial cells, and the medulla, where the majority of nonlymphoid cells are Ia-positive cells of hemopoietic origin. A few epithelial cells only are present in the thymic medulla. They are closely intricated with the sessile Ia-positive cells, whose precursors penetrate the thymus along with the lymphocyte progenitors and which are renewed in the course of thymic development. In contrast, the epithelial reticulum, expressing Ia both in the cortex and medulla, contributes a stable thymic component. During early thymic ontogeny, the hemopoietic cells expressed detectable levels of Ia antigen before the epithelial cell network.

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