Immature peritoneal mast cells in neonatal rats express the CTMC phenotype, as well as functional IgE receptors.

The purpose of this study was to investigate the relationship between the differentiation and maturation of mast cells and the expression of IgE receptors on their surface in neonatal animals in vivo. Another aim was to clarify whether connective tissue mast cells (CTMC) undergo a maturation process involving a transdifferentiation from mucosal mast cells (MMC) during this period of time. Mast-cell phenotypes were studied in terms of the profiles of proteinases and proteoglycan. In 1-week-old rats, the mast-cell granules stained with Alcian blue rather than with safranin (AB+/S-) in the Alcian blue/safranin staining sequence, normally regarded as a property of MMC. However, the AB+/S-stained proteoglycan was degradable by nitrous acid and stained with berberine sulphate, thus indicating that it contained heparin rather than chondroitin sulphate. The mast cells expressed rat mast-cell proteinase (RMCP) I rather than RMCP II, which is normally found in MMC. The mast cells of 1-week-old rats expressed functional IgE receptors, by showing a dose-dependent IgE-mediated histamine release of mast cells. About 70% of the IgE receptors on the mast cells were occupied by IgE. In 2- to 3-week-old rats, there was a progressive increase in mast cells stained with both Alcian blue and safranin or with safranin alone, i.e. they gradually changed towards the staining properties of CTMC (AB-/S+). The expression and the degree of IgE occupancy of the receptors increased in 1- to 3-week-old animals. This was paralleled by an increment in cell size and in the content of heparin, histamine and serotonin in the mast cells. The findings thus indicate that the peritoneal mast cells of neonatal rats express the CTMC phenotype and undergo a maturation process at from 1 to 3 weeks of age, without involving a transdifferentiation from MMC. The maturation of the mast cells is accompanied by an increase in the expression of functional IgE receptors on the cell surface. production was detectable as early as in 1-week-old rats.

[Differences in the structure of the posterior parietal (lumbar) lymphatic bed of the peritoneal cavity in human fetuses and newborns]. / Razlichiia v stroenii zadnego parietal'nogo (poiasnichnogo) limfaticheskogo rusla briushnoi polosti u plodov i novorozhdennykh cheloveka.

The study was performed in 150 corpses of human 8.5-36 wks old fetuses and 10 newborns using the complex of macro-microscopic methods. Primary lymphatic structures of lumbar region (sacs and canals) are transformed into lymphatic plexuses (9.5-10.5 wks) with the following formation of anlages of lumbar lymph nodes inside the invaginations. Variants of lumbar tracts and trunks structure arise during magistralization of lymphatic plexuses (14.5-19.5 wks) and reflect its depth and topographic variant. In intensive, medium and weak magistralization monomagistral, intermediate and plexiform forms develop. Topographic variant of magistralization provides the appearance of right-sided (20%), left-sided (20%) and relatively even bilateral (60% cases) organization of lumbar lymphatic bed on the whole.

Peritoneal lymphatic stomata of the diaphragm in the mouse: process of their formation.

BACKGROUND: Lymphatic stomata are channels connecting the peritoneal cavity with the lymphatics in the diaphragm. The process of sequential formation of the stomata has not been studied. The objective of this study was to examine the morphogenesis of the lymphatic stomata in mice. METHODS: Ultrathin sections of diaphragms from ddY mice obtained on embryonic day 18 and postnatal days 0, 4, and 10 were observed with a transmission electron microscope. RESULTS: By embryonic day 18 and postnatal day 0, lymphatics were already observed in the submesothelial connective tissue on the peritoneal side of the fetal diaphragm. The lymphatic endothelial cells, but not the mesothelial cells covering the diaphragm, protruded short cytoplasmic processes into the submesothelial connective tissue, and these almost reached the basal surfaces of individual mesothelial cells. By postnatal days 4 and 10, the lymphatic endothelial cells frequently protruded cytoplasmic processes into the submesothelial connective tissue, and the endothelial cell processes broke the continuity of both the basal lamina beneath the mesothelial cells and the submesothelial connective tissue. Neighboring endothelial processes formed a pair of U-shaped folds that were connected with each other via intercellular junctions at the apexes of the U-shaped folds. The disassembly of the intercellular junctions between the U-shaped folds was observed, and the basal surface of the mesothelial cell faced the lymphatic lumen. Dehiscence of the intercellular junctions between the mesothelial cells overlaying the lymphatics was observed, and lymphatic stomata were present. On the pleural side of the diaphragm, lymphatics were already present on embryonic day 18, but it was not observed that the endothelial process spanned the submesothelial connective tissue to the basal surface of the mesothelial cell. CONCLUSIONS: These results suggest the following process of the formation of the lymphatic stomata. (1) Neighboring lymphatic endothelial cells span the submesothelial connective tissue to the basal surfaces of mesothelial cells. (2) The lymphatic stomata are formed by the disassembly of the intercellular junctions between the neighboring endothelial cells and between the mesothelial cells overlying the endothelial cells.

Immunofluorescence analysis of B-1 cell ontogeny in the mouse.

In order to further understand the developmental aspects of B-1 cells, we characterized the ontogeny of this B cell population in the spleen and peritoneal cavity of BALB/c mice. Although there are B-1 cells in the spleen within the first 1-3 weeks after birth, they do not at any stage represent the majority of splenic B cells. Splenic B-1 cells reach peak levels at approximately 9 days after birth. The mesenteric lining that covers the small intestine of 7-day-old mice contains a population of IgM+ B cells, while at the same age, there are few lymphoid cells in the peritoneal cavity. Between 7 and 8 days after birth there is an influx of B cells into the peritoneal cavity. At 8 days, the first detectable peritoneal B cells appear to be of the B-1 type based on expression of IL-5 receptor and CD5. However, these peritoneal B-1 cells do not express Mac-1. This antigen is not expressed by the majority of peritoneal B-1 cells until 3 weeks. This study indicates that the majority of early splenic B cells are not B-1 cells and it suggests that the mesenteric tissues surrounding the gut contain B lymphocytes which traffic into the peritoneal cavity where they then reside.