T-lymphocytes in rat lymphoid follicles are a subset of T helper cells.
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Biomedical subjects
Publications and source records attributed to F G Kroese.
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The spleen of the snake Python reticulatus, was investigated as to its general histology as well as the presence of immune complex trapping cells both at the light and electron microscopical level. Histological examination revealed that the spleen of this reptile was encapsulated and contained some trabeculae. In the splenic parenchyma two different regions could be distinguished: viz. red and white pulp. The white pulp appeared to be arranged around "central arterioles" and their smaller branches extending towards the periphery of the white pulp. The red pulp was composed of blood sinusoids and cell cords. Electron microscopy revealed at least three types of non-lymphoid cells in the white pulp of the spleen of python: reticulum cells, forming the framework; some macrophages and dendritic cells predominantly located in the periphery of the white pulp. Of these types of non-lymphoid cells, only dendritic cells were able to trap and to retain intravenously injected horseradish peroxidase (HRP)-rabbit-anti-HRP immune complexes on their cell surface as determined by enzymehistochemistry at the light and electron microscopical level. These dendritic cells were frequently found in association with collagen fibres and did not engulf large quantities of carbon particles. These data suggest that dendritic cells in the spleen of the python might be the phylogenetic precursors of the mammalian follicular dendritic cells.
By means of immunohistoperoxidase techniques and the use of HRP-anti-HRP complexes, follicular dendritic cells in chicken spleen can be characterized both at the light-microscopical and ultrastructural level. In contrast to findings in mammals follicular dendritic cells in chicken spleen exhibit evident acid-phosphatase activity and possess considerable numbers of primary lysosomes. After intravenous injection of immune complexes a transient immune complex-trapping occurs in the peripheral parts of the Schweigger-Seidel sheath. The immune complex-trapping cells in the Schweigger-Seidel sheath and germinal centre show an identical enzyme histochemical pattern and only minor differences in ultrastructural characteristics. Shortly after intravenous injection of immune complexes and carbon particles these compounds show an identical distribution pattern; however, in the following days these distribution patterns become divergent.
Using horse-radish peroxidase (HRP)-anti-HRP immune complexes, 'antigen trapping' was studied in the spleen of the turtle, Chrysemys scripta elegans. It was found that antigen-trapping cells were situated in the periellipsoidal lymphocyte sheath of the white pulp only. The antigen-trapping cells have a dendritic character and a large lobulated nucleus. Carbon injections revealed that these cells do not phagocytose. The results are discussed with respect to the phylogeny of antigen-trapping cells.
The morphology of the spleen of the Red-eared Slider, Chrysemys scripta elegans, has been described. The outer surface of the spleen is covered by a thin fibromuscular capsule, from which a number of trabeculae extend into the parenchyma. The parenchyma of the spleen shows a definite demarcation into a red and white pulp. The white pulp is composed of two lymphoid compartments: lymphoid tissue surrounds both central arterioles and ellipsoids, forming the periarteriolar and periellipsoidal lymphocyte sheath (PALS and PELS, respectively). The ellipsoids consist of a thick layer of reticular tissue, enclosing a capillary with cuboidal endothelium. In contrast with the PALS, reticular fibers are rarely found in the PELS. Even after severe stimulation with paratyphoid vaccine, germinal centers are not found in the spleen of C.s. elegans. The red pulp of the spleen is composed of a system of venous sinuses and cords.
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Morphological and histochemical examination of the blood and connective tissue of the freshwater snail Lymnaea stagnalis injected with various types of foreign particulate materials has shown the existence of free as well as fixed phagocytic cells. The morphology of the fixed phagocytes is described, and the phagocytic system of the snail is compared with that of other molluscan species.
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Studies presented examine the origin of IgA plasma cells in B lineage chimeric mice constructed by reconstituting lethally irradiated mice with a mixture of syngeneic bone marrow cells and peritoneal cells from Ig heavy chain allotype congenic donors. In these mice, essentially all B cells in spleen and Peyer's patches are derived from the bone marrow donor; however Ly-1 B lineage cells which have been mainly detected in the peritoneum are derived from the peritoneal cell donor. Surprisingly, roughly half of the IgA plasma cells in the lamina propria of the gut are also derived from the peritoneal cell donor, suggesting an important role for peritoneally-derived B cells in the mucosal immune response.