Cell Migration and the Thymus

Sainte-Marie, G

doi:10.1007/978-1-4684-0919-2_7

Cited by 7 publications

(2 citation statements)

References 21 publications

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“…Estimates have been made of the number of cells leaving the thymus in several species of animals by measuring the content of lymphocytes in the thymic arterial and venous blood (16)(17)(18)(19). In addition, indirect measurements have been made of the extent of lymphocyte migration from the thymus by way of the lymph stream (20).…”

Section: Discussionmentioning

confidence: 99%

Lymphopoiesis and lymphocyte recirculation in the sheep fetus.

Pearson¹,

Simpson‐Morgan²,

Morris³

1976

The Journal of Experimental Medicine

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The production and the circulation of lymphocytes has been examined in the sheep fetus where neither foreign antigen nor immunoglobulins occur. It was found that as the lymphoid organs increased in size during fetal life, the numbers and the output of lymphocytes in the thoracic duct lymph increased. The recirculating pool of lymphocytes was estimated to be 5.5 +/- 1.5 X 10(8) cells in fetal lambs 95-100 days of age, 5.7 +/- 1.2 X 10(9) cells in fetuses 130-135 days of age, and 1.2 +/0 9.3 X 10(10) cells in fetuses near to term. The rate of addition of lymphocytes to the recirculating pool was 3.2 +/- 1.9 X 10(6) cells/h in fetuses of 100 days and 3.4 +/- 0.9 X 10(7) cells/h in fetuses of 130 days of age. Lymphocytes recirculated from blood to lymph in fetuses; labeled cells injected into the blood stream reappeared in the thoracic duct lymph promptly and reached maximum levels around 12-18 h after they were injected. Labeled lymphocytes were detected subsequently in greatest numbers in the lymph nodes, particularly in the mesenteric lymph nodes and in the interfollicular areas of the Peyer's patches. Chronic drainage of thoracic duct lymph from fetuses in utero for periods of up to 36 days had no obvious effects on the growth or development of the fetus and only minimal effects on the content of lymphocytes in the various lymphoid tissues even though the number of cells in the blood and lymph were reduced to between 20-30% of normal levels. Thymectomy done in fetuses about 2 mo befor cannulation of the thoracic duct reduced the output of cells in the thoracic duct to about 25% of normal levels and caused a significant reduction in the content of lymphocytes in the various lymphoid tissues. Thymectomized fetal lambs subjected to thoracic duct drainage for periods up to 2 wk in utero had a similar complement of lymphocytes in their lymphoid tissues to intact thymectomized fetal lambs. Lymphocytes obtained from the thoracic duct lymph of lambs thymectomized 2 mo previously recirculated from blood to lymph when they were injected intravenously, although they did this at a significantly slower rate than did lymphocytes from normal lambs.

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Section: Discussionmentioning

confidence: 99%

Lymphopoiesis and lymphocyte recirculation in the sheep fetus.

Pearson¹,

Simpson‐Morgan²,

Morris³

1976

The Journal of Experimental Medicine

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“…Other workers cannot differentiate reticulum cells from epithelial cells (Siegler and Rich, 1963;Smith, 1964). Although the lymphoid cell population makes up about 90% of the weight and 99.9% of the mitotic activity of the thymus (Metcalf, 1964), it represents a transient population of cells that (at least in part) originates in bone marrow, and seeds out into lymphoid organs after a period of residence in the thymus (Sainte-Marie, 1973). The thymus has a medulla composed of mixed epithelial, reticulum, and lymphoid cells; this is surrounded by a cortex in which tightly packed lymphoid cells are embedded in a meshwork of epithelial reticular cells.…”

Section: Unicentric Originmentioning

confidence: 99%

Immunopathology

1983

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Tridimensional reconstruction of the rat thymus

Sainte-Marie

1974

Anat. Rec.

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Some aspects of the basic histological features of the thymus are still not adequately known. The architecture of a heterogeneous organ, like the thymus, can be revealed by a tridimensional reconstruction only. We carried out such reconstruction of the cortex, medulla and network of interlobular septa of the rat thymus. The serial sections of a 10-week-old and of a 5-day-old thymus were projected on a cardboard of a thickness proportional to the magnification of the projection. The outlines of the three studied components were traced and cut off. The superposition of the similar cut-offs yielded a model of each of the three thymic components. The models demonstrated that the current description of the organ is not thoroughly realistic. It was found that there exists bridges of cortex crossing the medulla, whereas buds of medulla are present in the area generally occupied by the cortex. The relationship between the medulla and the cortex is more intricate than currently described. The results revealed that the interlobular septa do not form a network of more or less regular walls designed to divide a lobe into comparable lobules. Instead, this network is irregular, being related to the pathway of the main intrathymic blood vessels.The thymus of many species is formed of two lobes which, in fact, could be better considered as two adjacent organs, each lobe or thymus having its own connective tissue capsule (Siegler, '64). The organ is described as being compartmented into lobules by interlobular septa, which are extensions of the capsule penetrating deep into its parenchyma. The septa as known to be incomplete, so that the innermost part of a lobule is continuous with that of neighbouring lobules. The lobules are described or illustrated as being of a grossly comparable size, appearing somewhat like open and rounded alveoles. One component of the organ's parenchyma, the cortex, occupies the periphery of lobules, lining the capsule and the septa. The other component, the medulla, is described as a central mass giving rise to buds or branches, each occupying the middle of a lobule. Some observations led us to suspect that these current descriptions of the organ are not entirely realistic. The architecture of a heterogeneous organ such as the thymus can be revealed only by a tridimensional reconstruction. Accordingly, as a first step, we decided to carry out a tridimensional reconstruction of the cortex, the ANAT. REC., 179: 517-526. medulla, and the network of septa of the rat thymus. MATERIALS AND METHODSThe thymuses of two male Sprague Dawley rats, one 5-day-old and the other 10-week-old, were fixed in a variant of BouinHollande solution and processed for paraffin embedding. The organs were cut serially at 8 p, and sections were stained with the technique of Dominici. Both lobes of the younger rat and the left lobe of the adult rat were reconstructed, every fourth section being projected on cardboard that was proportional in thickness to the magnification of the projection. The limits of the medullary and o...

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Cell Migration and the Thymus

Cited by 7 publications

References 21 publications

Lymphopoiesis and lymphocyte recirculation in the sheep fetus.

Lymphopoiesis and lymphocyte recirculation in the sheep fetus.

Immunopathology

Tridimensional reconstruction of the rat thymus

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