Littoral cells of the lymph node sinuses in venous congestion based on scanning electron microscopic data

The littoral cells of the sinuses in the popliteal lymph nodes have been studied in Wistar rats under physiological conditions of hemodynamics and 1 h after ligation of the caudal vena cava. Intercellular clefts (1-4 mcm wide) are demonstrated to exist between the littoral cells of the internal wall of the marginal sinus. Presence of fenestrae in the peripheral thinned areas of cytoplasm is specific for these cells. The diameter of the fenestrae is 60-1,000 nm however, the fenestrae with the diameter up to 100 nm predominate. Lining of the medullar sinuses is also characterized by a high content of fenestrae, the maximal diameter of the fenestrae being the same as in the marginal sinus, although most of the fenestrae have the diameter 50-500 nm. No open intercellular clefts between the littoral cells of the medullar sinuses are revealed. In some cases, penetration of lymphocytes through the lining of the sinuses is observed. Under venous congestion, the diameter and amount of the fenestrae, size and amount of open intercellular clefts in the lining of the lymphatic sinuses increase significantly. This demonstrates its increasing permiability, having an essential importance for compensation of circulatory disturbances in the zone of the venous congestion.     

Peritoneal macrophages introduced into mouse foot pads enter the germinal center of regional lymph nodes nonspecifically.

Male mice were injected into their foot pads with sheep erythrocytes (SRBC) to form lymph follicles in the germinal centers in the popliteal lymph nodes. 4 weeks later, peritoneal macrophages labeled with carbon from syngeneic donors sensitized with SRBC or typhoid-paratyphoid bacilli (TAB) were separately injected into the foot pads as well. The popliteal lymph nodes were histologically examined at 6 h to 5 days after injection. Labeled macrophages appeared in the marginal sinus, migrated straight across the cortex from the marginal sinus to the lymph follicles and then entered the germinal centers. There was no difference in the mode of appearance, migration and localization of labeled macrophages in the regional lymph nodes between the mice given labeled macrophages from SRBC-sensitized donors and those given macrophages from TAB-sensitized donors. The entrance of lymph macrophages into the germinal centers of the regional lymph nodes would be immunologically nonspecific. After the injection of Pelikan ink into the foot pads, the macrophages which have taken up carbon in the peripheral tissue reached the regional lymph nodes via the afferent lymphatics and then entered the germinal centers, mainly through the medullary pole of the lymph follicles, after migrating along their immediate exterior from their marginal sinus to their medullary pole.     

Interrelationships of B- and T-cell areas in peripheral immune organs of the albino rat after hind limb autotransplantation

Using 68 3-month-old male albino rats, it was established that the pattern of the changing interrelationships of B- and T-cell areas in the spleen and in the popliteal, inguinal and medial iliac lymph nodes regional for the experimental limb during the initial stage after hind limb autotransplantation, with or without sciatic nerve alloplasty, represents a universal type of initial response of the peripheral immune organs to external challenge which takes place in three steps: 1) an increase in the number and size of the lymph nodules, 2) enlargement of T-cell areas, 3) an increase in the number of structures containing antibody-forming cells (the medullary cords in the lymph nodes and the splenic cords). Sciatic nerve alloplasty gives rise to expansion of the medullary cords in the lymph nodes and the marginal zone and cords in the spleen, with parallel significant enlargement of T-cell areas.     

Structural organization of the compensation process in the lymph nodes in venous stasis

Transmission and scanning electron microscopy was used to study the structural organization of the lymph nodes during venous congestion. At the early period (1 h of venous congestion) one could see an increased number of the fenestrated cells in the venous part of the capillary whereas at the later period (after 6 h to 3 days) a rise of the microvesicular transport via endotheliocytes of the arterial part of the capillary and via fenestras of the venous part. Within 7 to 14 days one could see activation of the microvesicular transport via the indicated parts of the capillary. At all the stages of venous congestion the fluid contained by the parenchyma of the lymph node penetrates via fenestras and intercellular fissures to the marginal sinus, while only via fenestra to the cerebral sinuses.     

Morphofunctional reorganization of the kidneys in lymphatic outflow disturbance

In 115 Wistar male rats structures and rates of tissue blood flow have been studied in the cortical and medullary renal substance histologically, polarographically (estimation of the volumetric tissue blood flow by hydrogen clearance). Systemic arterial (peritoneal aorta), venous (caudal vena cava) and lymphatic (renal lymph nodes) pressures have been measured, normal and after ligation of the thoracic duct at early (1-3 days), middle (1 month) and late (2-3 months) periods. In 1-3 days edema and dystrophy of the renal parenchyma, decrease of the blood flow rate in the cortical and its increase in the renal medullary substance, as well as a sharp elevation of pressure in the lymph nodes are observed. In 1 month of the experiment together with dystrophy and edema moderate sclerosis, decreasing blood flow rate in the cortical and medullary substance are noted. Increase of the systemic arterial and venous pressure and decreasing pressure in the lymph nodes, as well as a sharp increase of the renal nodes mass are revealed. In 2-3 months of the experiment, together with sclerosis of the renal parenchyma, elevated blood flow rate is observed in the kidneys and decreasing pressure in the lymph nodes up to its initial value takes place.     

Structural changes in the lymph node sinuses in acute blood loss]

By means of light and scanning electron microscopy sinuses of the popliteal lymph nodes have been studied in 50 Wistar male rats. After modelling of an acute hemorrhage in the animals (in 15, 120 min and 1 day) volume of the medullary and marginal sinuses increases essentially, while blood stream intensity decreases in peripheral tissues. Amount of fenestrae in the sinusal lining decreases, that is, perhaps, caused by edema of cytoplasm in the lining cells and accompanied with formation of numerous cytoplasmic protrusions into the sinusal lumen. In 3 days the blood stream level in the peripheral tissues restores, structural organization of the littoral cells in the lymphatic sinuses normalizes. The data obtained demonstrate that during the first day after the acute hemorrhage decrease of hematolymphatic exchange intensity in lymph nodes and enhancement of transitory lymph flow in them take place.     

S-100-immunoreactive giant macrophages in lymphoid tissues of the guinea pig

Giant cells containing S-100 protein of the lymphoid tissues in the guinea pig were studied by immunohistochemistry using S-100 antiserum. S-100-immunoreactive giant cells were dendritic in shape, contained one or two irregular-shaped, euchromatic nuclei, phagosomes of various diameter, numerous mitochondria and microfilaments in the perikaryon, and extended cell processes free of cell organelles. These cells predominantly lined the superficial cortex facing the subcapsular sinus, were less numerously scattered in the medulla of lymph nodes and located at the marginal zone of the spleen. They also stained with S-100 alpha monoclonal antiserum and showed active phagocytosis for aldehyde-fixed red cells or colloidal carbon in the popliteal lymph node and spleen. S-100-immunoreactive giant cells also appeared in the corticomedullary zone of the thymus and in the interfollicular area of the Peyer's patches of the gut. Small sinus macrophages, which exhibited active phagocytosis for colloidal carbon but were less active for red cells in the popliteal lymph node and spleen, were not stained with S-100 antiserum. These findings indicate that S-100-immunoreactive giant cells of the lymph node and spleen are a subpopulation of macrophages different from S-100-negative cells of the small type.     

Ultrastructural organization of the endotheliocytes of iliac lymph node capillaries in pregnancy (morphometric study)

Using light and electron microscopy and morphometry, the morphological changes in the lymph nodes of arterial and venous parts of capillaries were studied on the 11th, 17th and 21st days of pregnancy in rats. Ultrastructural changes in endothelial cells of blood vessels in the uterine lymph nodes during normal pregnancy are of adaptive nature and are possibly responsible for the relief of the blood congestion in the system of the inferior vena cava and for the improvement of the utero-placental circulation.     

Structural changes in popliteal lymph nodes in the graft vs. host reaction to H-Y antigen in male C57BL/6-strain mice

Regional popliteal lymph nodes in intact, control and experimental (I, II, III groups, respectively) have been studied by means of the morphometric method in male C57Bl/6 line mice at the pick of the reaction produced by injection of spleen cells and mesenteric lymph nodes obtained from syngenic females and repeatedly immunized to H-Y antigen (10 animals in each group). Injection of the cell suspensions from the immunized and intact females of the C57Bl/6 mice result nearly in two-fold increasing mass of the regional popliteal node at the expense of enlarged size of all its zones. Changes in cytoarchitectonics of the node structural components result from redistribution of certain cellular elements. The essential changes in the cell composition of the lymph nodes in the II and III male groups are accompanied with an increasing part of the stromal reticular cells. Simultaneously, content of small lymphocytes decreases significantly. In the III group of mice there is a sharp increase in the content of young forms of the lymphoid line cells in all structural components of the node, as well as in eosinophilic granulocytes in medullary cords. In the dark cortical zone of the nodes (III group) there occur tissue basophils (mast cells), that, together with increasing number of acidophilic granulocytes and appearance of neutrophilic cells, demonstrates that there is an inflammatory reaction in the organ studied as a response to the lymphocytic suspension injected. In the experimental group of the animals a complete disappearance of plasma cells is noted in the node cortex, but some increase of their part takes place in the medullary cords.     

Degree of chromatin activity and the RNA level in lymphocytes of popliteal lymph nodes of dogs after administration of an antigen]

In the experiment performed on 127 dogs by means of cytospectrofluorometric analysis, using fluorochrome acridine orange in dynamics up to 1 year, changes in the level of chromatin activation and RNA content have been studied in lymphocytes of the germinative centers and the crown of lymphoid nodules, in the paracortical zone and medullary cords of the regional and contralateral popliteal lymph nodes, after subcutaneous injection of antigen (BCG vaccine, 0.2 mg/kg) into the lateral area of the foot of the left pelvic extremity. The immune response is accompanied with a periodical increase in the level of chromatin activation and RNA content in populations of lymphocytes in the regional and contralateral popliteal lymph nodes with maximum in 6 h, 3-7 days, 1-3 months after the antigen injection. The intensity of these processes has an unequal level in lymphoid cells of various structural components; it is higher in lymphocytes of the contralateral lymph node.     

Structural-functional transformations of the ileal lymph nodes in pregnancy complicated by blood loss]

The microanatomic organization of iliac lymph nodes was studied in 24 pregnant Wistar rats (pregnancy term 21 days) after simulation of acute hemorrhage in them. A considerable decrease of a relative area occupied by a marginal sinus was revealed. This shows transport functional changes of lymph nodes in pregnancy complicated by hemorrhage.     

Germinal centers and the B-cell system

Summary Germinal centers of the rabbit appendix were studied for the presence of complement receptors, immunoglobulin and alkaline phosphatase. In popliteal lymph nodes, de novo-developing germinal centers were studied with respect to these markers up to 21 days after sheep red blood cell (SRBC)-stimulation. In addition, the possible presence of antigen (SRBC) receptor-bearing cells in these germinal centers was investigated.The results may be summarized as follows: 1) Germinal centers in the appendix as well as those in popliteal lymph nodes were rich in complement receptor-bearing cells. Complement-receptor density did not significantly change during a germinal-center reaction. 2) Immunoglobulins were present only at very low densities on the surface of lymphoid cells in the densely populated area of germinal centers. In germinal centers of popliteal lymph nodes lymphoid cells in the thinly populated area again showed higher densities. Immunoglobulins possibly complexed with antigen on the surface of follicular dendritic cells were not observed in the initial phase of a germinal center reaction. In contrast, in germinal centers of the appendix, immunoglobulin was present in excessive amounts throughout the thinly populated area, possibly complexed with antigen, which is also abundantly present. 3) Reticular staining patterns of alkaline phosphatase were present in the densely populated area, but absent in the thinly populated area of germinal centers in both appendix and popliteal lymph nodes. Primary follicles and young germinal centers were alkaline phosphatase-negative. 4) Antigen receptor-bearing cells were detected in germinal centers of popliteal lymph nodes as early as 5 days after SRBC-stimulation, reaching a maximum at day 10.In conclusion, with the present experimental approach, microenvironmental differences were shown between the densely populated area and the thinly populated area of germinal centers. However, no indication was obtained for a postulated maturation event of the lymphocytes within germinal centers, or for functional differences that may exist between germinal centers in the appendix and popliteal lymph nodes.     

Morphometric study of the ultrastructural organization of the endotheliocytes of blood capillaries in the iliac lymph nodes of pregnant rats

The ultrastructure of blood capillary endotheliocytes of iliac lymph nodes during pregnancy was investigated in rats. It was found that changes in microcirculation during pregnancy are accompanied by the appearance of the adaptive changes at all levels of lymph node structural organization. They are: increased lumen of arterial and venous part of the capillaries, increased intermediate sinus volume, increased fenestration of both parts of capillaries, a sharp increase in the number of micropinocytous vesicles and activation of transendothelial channel formation.     

High endothelial venules of the lymph nodes express Fas ligand.

Fas (CD95, APO-1) is widely expressed on lymphatic cells, and by interacting with its natural ligand (Fas-L), Fas induces apoptosis through a complex caspase cascade. In this study we sought to survey Fas-L expression in vascular and sinusoidal structures of human reactive lymph nodes. Immunohistochemical Fas-L expression was present in all paracortical high endothelial venules (HEVs), in cells lining the marginal sinus wall, and in a few lymphocytes, but only occasionally in non-HEV vascular endothelium. In the paracortical zone over 60% of all vessels and all paracortical HEVs showed Fas-L expression, whereas in the medullary zone less than 10% of the blood vessels were stained with Fas-L. Normal vessels outside lymph nodes mostly showed no Fas-L expression. We show that in human reactive lymph nodes Fas-L expression is predominantly present in HEVs. Because the circulating lymphocytes gain entry to nodal parenchyma by transendothelial migration through HEVs, the suggested physiological importance of Fas-L expression in these vessels lies in the regulation of lymphocyte access to lymph node parenchyma by possibly inducing Fas/Fas-L mediated apoptosis of activated Fas-expressing lymphoid cells. The Fas-L expressing cells in the marginal sinus might have a similar function for cells accessing the node in afferent lymph.     

Functional morphology of the lymphatic system of the rat uterus during pregnancy

In the regional lymph nodes of the uterus the comparative volume of the paracortical zone significantly increases, especially within the period of the 13th-17th days of pregnancy. In the popliteal lymph node similar effect is not discovered. From the 7th up to the 11th day edema, vasodilatation, infiltration with special leucocytes are revealed. Endothelium of the postcapillary venules is hypertrophied, contains many migrating lymphocytes, which accumulate around the vessels mentioned. The volume of the microcirculatory bed is moderately increased. By the 17th day plasmoblasts, plasmocytes, Motta's cells, monocytes and especially macrophages appear in the paracortical zone. In B-zones and in medullary sinuses blasts, plasma cells, monocytes, macrophages, mitotically deviding cells increase in number. The part of the reticular cells decreases. The tensometric method demonstrates an increasing pressure of lymph in the iliac lymph node at pregnancy. Collateralies appear in the ovarian vein system, in the broad ligament of the uterus, in the lumbar area. The uterine vascular system is supposed to participate in adaptation to pregnancy. In genesis of the regional lymph node changes, discirculatory shifts, predominating during placental organogenesis, combine with phenomena of cell migration and proliferation (clearly revealed by the time when formation of the placenta is completed).     

Ontogeny of the antigen-reactive lymph follicle-forming capacity of the popliteal lymph node in neonatal mice

The ontogenetic development of the reactive lymph follicle-forming capacity of the popliteal lymph node was investigated immunohistochemically in young mice which had received a single injection of hemocyanin (KLH) in a rear footpad at a predetermined age (between 1 and 21 days). The mice were sacrificed at various intervals after injection. In non-stimulated young mice, primary lymph follicles first appeared in the popliteal node at 11 days of age. When KLH was given to 7-day-old or older mice, each draining popliteal node showed a marked increase in B lymphocytes in the extrafollicular zone 3 days after injection and produced a number of "new" lymph follicles outside the pre-existing follicles over the next few days. In mice injected at 2-4 days of age, these nodes showed an increase in B lymphocytes in the outer cortex and had produced several lymph follicles by 8 days of age. The number of lymph follicles produced by each node tended to increase in line with age at injection. These results indicate that neonatal popliteal nodes become able to produce lymph follicles in response to exogenous antigens some time before ontogenetically developing follicles appear. The formation of new lymph follicles observed in draining popliteal nodes after KLH injection at an early postnatal age is discussed in relation to the ontogenetic development of stromal cells (precursors of follicular dendritic cells) that are capable of interacting with B lymphocytes and the extent of B lymphocyte influx into the node induced by KLH stimulation.     

Pathomorphologic characteristics of the regional lymph nodes in hydronephrosis]

The dependence of pathomorphological changes in the regional lymphatic ganglia of the dog's kidney upon the duration of experimental hydronephrosis is shown. The development of necrosis in some of them points out indirectly to the participation of the renal lymphatic system in carrying off the urine saturated with toxic products persisting in it for a long period. Increased dilatation of intermediate and medullary sinuses is connected with continuous inflow of the lymph that contributes to its congestion and then leads to the retrograde flow. A mechanical obstraction appears on the way of lymph and this fact aggravates mechanical insufficiency of the lymph circulation. At the same time this particular case is lymphogenic sclerosis, which is induced by acumulation of disturbed metabolism products in the intermediate tissue brought by the lymph.     

The influence of strong transplantation antigens (Ag-B) on lymphocyte migration in vivo.

The tissue localization of syngeneic thoracic duct lymphocytes was compared to that of allogeneic cells in four rat strain combinations differing at the Ag-B locus (HO → DA, DA → HO, AO → HO, HO → AO). Dual isotope labeling with [³H]uridine and [¹⁴C]uridine was applied in order so that the distribution of allogeneic and syngeneic cells could be followed in one recipient. During the first couple of hours after iv injection, allogeneic lymphocytes usually migrated as easily into the various tissues as did syngeneic cells. However, after 24 and 48 hr, a reduced amount of label associated with allogeneic cells was often measured in the tissues. This reduction differed in magnitude in the different strain combinations and was most pronounced in the lymph nodes. A reduced number of allogeneic cells also appeared in the thoracic duct. By contrast, no reduced localization of allogeneic lymphocytes was measured in the draining popliteal lymph nodes late after sc injection. In preimmunized animals allogeneic cells were rapidly removed from the blood and therefore failed to localize in the lymphoid tissues. Furthermore, the lymph node localization of allogeneic cells was more like that of syngeneic cells in splenectomized rats, as well as in irradiated recipients (when the irradiation was given shortly before cell transfer). It is concluded that transplantation antigens play no essential role in the interaction between recirculating lymphocytes and the venous endothelium at the sites where the large-scale physiological emigration of the cells takes place (the HEVS of the lymph nodes and the marginal zone vessels of the spleen). The elimination of allogeneic cells is found later; it probably takes place in the lymph nodes and spleen. Possible mechanisms responsible for this rapid removal of allogeneic lymphocytes in nonimmunized recipients are discussed.     

Structure of sinuses in the human lymph node

Summary A casting technique has been employed to display in three dimensions, the lymphatic microcirculation within the human lymph node. The casting compound filled the marginal sinus, and diffusely permeated the cortical lymphoid parenchyma. However, deep within the lymph node in the medullary region, the medium remained within the limits of the sinus walls. The casts showed well-defined channels appearing similar to vessels. These converged into larger vessels, which drained into efferent lymphatics leaving the node at the hilus.Electron microscopic examination showed that the outer wall of the marginal sinus and the trabecular side of trabecular sinuses had an intact, continuous endothelium with a basement membrane. However, gaps were present in the inner wall of the marginal sinus, as well as in the parenchymal wall of the trabecular sinus. In the medulla, the sinuses were lined by endothelial cells which appeared similar to macrophages. The sinus lining was incomplete and possessed numerous perforations. These observations indicated that sinus walls adjacent to connective tissue served as a barrier to cell movement, but those adjacent to a large lymphoid cell population had gaps, with cells in apparent transit between sinus lumen and parenchyma.     

Catecholamine and serotonin content in the lymph nodes following deafferentation

Using Falck fluorescent technique in combination with microspectrofluorometry the measurement of catecholamine and 5-hydroxytriptamine level was performed in popliteal lymph nodes of normal dogs and 2 weeks after deafferentation. Maximal catecholamine and 5-hydroxytriptamine content was observed in adrenergic nerve fibers, elements of trabecular-elastic complex and monoaminocytes of medullary substance of intact animals. Biogenic amine level decreased deafferented limb lymph nodes. Monoamine imbalance according to divergent type was registered in a colateral limb, i. e. 5-hydroxytriptamine level was increased and catecholamine level was decreased.