Histology and Ultrastructure of the Lymph Nodes of the Buffalo (Bos bubalus)

Pre‐scapular, femoral and mesenteric lymph nodes from five buffalo calves and five buffalo bulls were studied using light and transmission electron microscopy. The nodes were surrounded with a thin capsule of dense connective tissue and smooth muscles. Subcapsular and trabecular lymphatic sinuses were lined with endothelial cells resting on a basement membrane. The cortex was formed by lymphoid follicles and inter‐follicular lymphocytes. Primary and secondary follicles were observed. The medulla was made up of medullary cords of lymphocytes separated by lymphatic sinuses. These sinuses were lined with a discontinuous epithelium and interestingly crossed by reticular fibres. High endothelial venules were found in the paracortical area. Several lymphocytes were observed infiltrating the wall of these venules. The lymph nodes of the Egyptian water buffalo showed a typical structure compared with the majority of mammals, with no age‐related structural variation.     

Histological, histochemical and immunohistochemical study of the haemal nodes of the dromedary camel

Haemal nodes are lymphoid organs found in various mammals and some birds. The structure of haemal nodes has been described in a number of species but not yet in the camel. Therefore, haemal nodes from 10 camels were studied histologically and tested for CD3, CD22, major histocompatibility complex (MHC) class II/DR, alpha-smooth muscle actin and for the demonstration of acid and alkaline phosphatases. The haemal nodes were of spherical or kidney shape with one or two hili and had a capsule and trabeculae of connective tissue and smooth muscles. The main parenchyma was composed of a cortex and a medulla. The cortex was formed from lymphoid follicles and diffuse interfollicular lymphocytes. The medulla consisted of lymphoid cords separated by medullary sinuses. The interfollicular lymphocytes and those in the medullary cord were CD3-positive. The lymphoid follicles showed CD22-positive cells. MHC class II/DR was expressed by most cells of the parenchyma. There were also subcapsular, peritrabecular and medullary blood sinuses. Afferent and efferent lymphatics and lymphatic sinuses were also found. Acid phosphatase-positive cells were localized mainly in the marginal, the interfollicular zone and in the medullary cord. Alkaline phosphatase positivity was observed in the endothelium of the sinuses and in the lymphoid follicles. The morphology of these organs in the camel allows a classification as haemolymph nodes and suggests involvement in blood and lymph filtration.     

山羊咽扁桃体和咽鼓管扁桃体的组织结构观察

选取健康10月龄奶山羊10头,断头宰杀后取咽扁桃体和咽鼓管扁桃体,应用组织学光镜和电镜制片技术研究咽扁桃体和咽鼓管扁桃体的显微和亚显微组织结构.结果表明:山羊咽扁桃体和咽鼓管扁桃体的黏膜上皮主要由2～3层多边形上皮细胞组成,部分区域只有单层扁平细胞,相邻上皮细胞间空隙很大,上皮细胞表面有丰富的微绒毛.上皮细胞之间和黏膜上皮下方固有层内有大量淋巴细胞浸润.扁桃体的实质部分由数个次级淋巴小结和弥散淋巴组织构成,弥散淋巴组织中有大量分布的淋巴管和毛细血管后微静脉.此外,在紧贴黏膜上皮细胞下方的固有层和淋巴滤泡中可观察到少量的树突状细胞.结果提示山羊的咽扁桃体和咽鼓管扁桃体可作为鼻腔免疫的主要诱导位点和效应部位.     

Histology, immunohistochemistry and ultrastructure of the equine palatine tonsil

The palatine tonsils of five young horses formed 10-12 cm elongated follicular structures extending from the root of the tongue on either side to the base of the epiglottis and lateral to the glossoepiglottic fold. The stratified squamous non-keratinized epithelium of the outer surface was modified into crypts as reticular epithelium by heavy infiltration of lymphoid cells from underlying lymphoid follicles. In places, lymphoid tissue reaching almost to the surface and with only one to two cell layers intact was identified as the lymphoepithelium. Langerhans cells with Birbeck granules were interspersed between epithelial cells. Lymphoid tissue organized in lymphoid follicles constituted the parenchyma of the palatine tonsil. CD4-positive cells were more numerous and CD8-positive lymphocytes less numerous compared with their distribution in the lingual tonsil. B cells and macrophages were also more numerous than in the lingual tonsil and lectins showed a different pattern of attachment. M cells were not observed. High endothelial venules with well-developed vesiculo-vacuolar organelle had structural evidence of transendothelial and interendothelial migration of lymphocytes. Striated muscles as seen in the deeper lamina propria mucosae of the lingual tonsil were absent. The immunohistological and ultrastructural characteristics of the equine palatine tonsil are similar to those of humans but differ from those of the lingual tonsil and are consistent with a role as an effector and inductor immunological organ.     

The parotid, mandibular and lateral retropharyngeal lymph nodes of the camel (Camelus dromedarius)

The parotid, mandibular and lateral retropharyngeal lymph nodes of the dromedary camel were examined using both light and electron microscopy. All three lymph nodes were lobulated. They did not show the characteristic medulla, cortex and paracortex of typical lymph nodes. Instead, they contained lymphatic nodules, dense anodular lymphoid tissue and diffuse lymphoid tissue dispersed throughout the lymph node. Networks of sinuses were present in the diffuse lymphoid tissue. The diffuse lymphoid tissue in the periphery of all lymph nodes examined was characterized by numerous erythrocytes within and around its network of sinuses. The nodal sinuses were contiguous with the septal vessels, which are considered the possible source of erythrocytes seen in this study. The lymph nodes that were seen in this study resembled the haemolymph nodes of other mammals with regard to their content of erythrocytes but were unique in being located in sites that were typical of ordinary lymph nodes. Morphometric analysis has shown that the percentage volume densities of the stroma and the various parenchymal components were similar in the three lymph nodes.     

Theileria parva infection in calves causes massive lymphocyte death in the thymus, spleen and lymph nodes without initial proliferation

In a study of trends and magnitudes of lymphocytes proliferation, destruction or apoptosis eleven 3-month-old healthy calves were experimentally infected with the protozoan parasite Theileria parva, which is reported to cause lymphocyte proliferation. Four control calves were not infected. Infected and non-infected calves were sacrificed on days 9, 12, 16, 19, 23, 24 and 25 to examine lymphoid tissue changes and lymphocyte proliferation, apoptosis or necrosis in the thymus, spleen and lymph nodes. All infected calves developed severe East Coast fever, with enlargement of lymph nodes, dyspnoea, high fever and pulmonary oedema. Lymphocyte proliferation was not observed in lymph nodes, thymus and spleen; instead there were massive deaths of lymphocytes and other cells. The terminal severe disease caused massive lymphoid parenchyma coagulation terminating with caseation, organs and cells being undeterminable histologically. Tissues surrounding the lymph nodes were oedematous. Lymph node and thymus parenchyma were caseated and cortices and medulla indistinguishable because of severe lymphocyte and accessory cell deaths. The lymph node fibrous reticular stroma was necrotic and caseated. Lymphoid follicles in lymph nodes degenerated and lacked germinal centres. Lymph nodes, spleen and thymus were grossly enlarged, hardened, potato or cheese like, but microscopically very hypocellular and in the terminal disease acellular because of massive lymphocytes destruction. In the thymus there was extensive thymocyte and epithelioid cell necrosis and loss of distinction between cortex and medulla. The spleen white and red pulps were indistinguishable because of extensive lymphoid cell necrosis. The white pulp degenerated more than the red pulp. The massive lymphocyte deaths in the lymph nodes, thymus and spleen, without lymphocyte proliferation in this T. parva infection in calves leads to a conclusion that this parasite is lympho-destructive and lympho-degenerative in vivo rather than lympho-proliferative.     

Lymph Drainage from the Ovine Tonsils: An Anatomical Study of the Tonsillar Lymph Vessels

Although the tonsils of sheep have gained much attention during the last decade, only few data are available on their lymph vessel architecture. Tonsillar lymph vessels are immunologically important as they form the efferent routes for locally activated immune cells to reach the draining lymph nodes. To gain insight into the tonsillar lymph drainage in the sheep, Indian ink and a casting polymer were injected into the interstitium of the five tonsils present in the heads of slaughtered sheep. This enabled us to determine the draining lymph node and to examine the microscopic organization of lymph vessels using light and scanning electron microscopy. No lymph vessels were observed within the tonsillar lymphoid follicles. The corrosion casts demonstrated that the lymphoid follicles are surrounded by numerous sacculated lymph sinuses that drain into a dense interfollicular lymph vessel network. From here, the lymph flows into single small lymph vessels that in turn drain into larger lymph vessels extending towards the medial retropharyngeal lymph node. The presented results can be valuable for immunological studies, for example during oral or intranasal vaccine development.     

Distinctive peripheral lymph node hyperplasia of young cats

Peripheral lymph node enlargement was found in 14 of a series of 132 feline lymph node biopsy specimens. Six of nine cats tested had antibodies for feline leukemia virus (FeLV). Half of the cats were clinically normal while the remainder had fever, lethargy, anorexia, and hepatosplenomegaly. There was severe distortion of lymph nodal architecture with variable loss of discernible follicles and sinuses. Histiocytes, lymphocytes, immunoblasts, and plasma cells were present in expanded paracortical regions which encroached on, and occasionally effaced, lymphoid follicles. Postcapillary venules were numerous and prominent throughout the paracortex. The lymphadenopathy was most commonly transient (86% of cases) with subsequent development of lymphoma in one cat. Lymph nodes from seven kittens with experimental FeLV infection were compared with spontaneously enlarged lymph nodes; four of seven had B and T lymphocyte hyperplasia with normal nodal architecture. Three had partial loss of nodal architecture as a result of expanded paracortical regions populated largely by histiocytes and lymphocytes. Proliferation of postcapillary venules was not prominent in nodes from FeLV-infected cats. The cause of spontaneous lymph node hyperplasia of young cats was not determined. However, the similarity of lesions to those of kittens with experimental FeLV infection and the association with FeLV by serologic tests in six of nine cats suggest that this retrovirus may be involved in the pathogenesis of the lesion.     

A Scanning and Immunohistochemical Study in Bovine Haemal Node

The bovine haemal nodes are lymphatic organs with haemal circulation. The blood circulates inside of them through virtual cavities named sinuses. In these sinuses there is passage of cells and particulate materials from parenchyma to sinuses and vice versa. For this passage temporal overtures exist in the sinus walls. The sinus wall is composed of endothelial cells, basal membrane and reticular cells. Our results have demostrated that type IV collagen was one of the basal membrane constituents in bovine haemal nodes and by this constitution a dynamic equilibrium of the sinus walls was permitted.     

Morphology of the lymph nodes in bottlenose dolphin (Tursiops truncatus) and striped dolphin (Stenella coeruleoalba) from the Adriatic Sea

Morphology of the lymph nodes was examined in six bottlenose dolphins (Tursiops truncatus) and three striped dolphins (Stenella coeruleoalba) from the Adriatic Sea. All animals had been found dead in nature. One group of the nodes was taken from the tracheal branching area and was marked as bifurcational lymph node, and the other group was taken from the mesenteric root and was marked as mesenteric lymph node. Microscopic analysis showed that the lymph nodes in both dolphin species were surrounded by a connective tissue capsule comprising smooth muscle cells. The parenchyma of the mesenteric and bifurcational lymph nodes in bottlenose dolphin was divided into the peripherally situated cortex with the lymphatic nodules and diffuse lymphatic tissue, and the centrally situated medulla structured of the medullary cords separated by the medullary sinuses. These lymph nodes structurally correspond to the lymph nodes in the majority of terrestrial mammals. The mesenteric lymph node of striped dolphin also had a peripherally situated cortex and a centrally positioned medulla as the majority of terrestrial mammals. In the bifurcational lymph nodes of striped dolphin, there was a central dense lymphatic tissue with the lymphatic nodules and a peripheral less dense lymphatic tissue structured of the cell cords and sinuses. The bifurcational lymph node in striped dolphin resembled porcine lymph nodes and belonged to the inverse lymph nodes.     

Morphologic features of lymph vessels in caprine hemal nodes

The distribution and characteristics of lymph vessels in caprine hemal nodes were studied after glutaraldehyde fixation and epoxy resin embedding. Histologically, the lymph vessels were characterized by thin walls and wide lumens containing inspissated lymph in which a few cells were suspended. The lymph vessels contrasted sharply with adjacent blood sinuses that were filled with elements of circulating blood. A circumferential lymph vessel in the cortex joined radial branches in the medulla that met at the hilum to drain through a large efferent lymph channel. Ultrastructurally, the lymph vessel wall comprised endothelial cells supported by a continuous basal lamina, collagen fibrils, and adventitial reticular cells. The cytoplasm of endothelial cells had fenestrations, plasmalemma-associated vesicles, vacuoles, and focal splits that enclosed large compartments. Many compartments contained erythrocytes and lymphocytes. Modifications of the endothelial cells signified their endowment with features that favored transendothelial transport. The distribution of lymph vessels and the finding of only efferent lymph channels are related to the roles of hemal nodes in blood storage by hemoconcentration and in immune defense mechanisms.     

Estudio Histoquímico e Immunohistoquímico del Tejido Linfoide Porcino: Ganglio Linfático, Bazo y Timo

Immunohistological (S-100, cIg) and enzyme histochemical (ANAE/ANBE, beta-glu, ATPase, AcP) investigations were carried out to identify lymphocyte and reticular cell subpopulations "in situ", in pig lymphoid tissue (lymph node, spleen, and thymus) of a 6 months old group, and a 6-9 days old one. By means of immunohistological techniques, in the 6 month old pigs we could detect S-100 protein (PAP), chiefly in T-areas lymphocytes, but we also found some S-100 positive lymphocytes in spleen follicles. Also S-100 protein were detected at Follicular Dendritic Cells (FDC) in lymph node and spleen; and Reticular Fibroblastic Cells (RFC) only in the first one. Finally, S-100 were noted in Hassall corpuscles (thymus), nervous fibres, and endothelial cells too. Using PAP (IgG, IgM) and IPI (IgA) techniques we could detect lymphocyte cytoplasmatic surface immunoglobulins (cIg) in lymphocytes, lymphoblastoid and plasmacytoid cells in nearly all tissue compartments. By means of histochemical techniques we could identify T-area lymphocytes ANAE/ANBE and beta-glu positives (cytoplasmatic spots) and B-area lymphocytes ATPase positive; macrophages, and polymorphonuclear eosinophiles PHNE being ANAE/ANBE and beta-glu positives (diffuse cytoplasmic stain); and Hassall corpuscles ANAE/ANBE and AcP positives. Concerning to reticular cells, we found FDC and RFC in lymphoid follicles, and Interdigitating Reticular Cells (IDC) in lymphoid diffuse tissue, with enzyme activity (all the enzymes studied) in nearly all the cases. In piglets, the immunohistological and histochemical pattern was nearly the same.     

Immunohistochemical MHC-II and interleukin 2-R (CD25) expression in lymph nodes of pigs with spontaneous postweaning multisystemic wasting syndrome (PMWS)

Immunohistochemical expression of immunocompetent cells bearing major histocompatibility complex (MHC-II) and interleukin 2-R (IL2-R) (CD25) molecules was performed on lymph nodes with spontaneous postweaning multisystemic wasting syndrome (PMWS). Control lymph nodes displayed intense diffuse immunoreactivity to MHC-II in both follicles and interfollicular areas. A marked reduction of follicular MHC-II immunoreactivity and inconsistent staining of histiocytes in interfollicular areas was observed in PMWS cases with a slight lymphoid depletion; in those cases with moderate to severe lymphoid depletion, there was a progressive decrease in MHC-II expression. In controls and in slightly depleted nodes, IL2-R was equally expressed in interfollicular tissue and in follicles, whereas in moderate and severe cases, it was detected in interfollicular remnants only. Immunohistochemical staining was scored semiquantitatively. The mean MHC-II score was significantly reduced in PMWS cases compared with controls (Spearman test), whereas there was no difference in the IL2-R score. The evident reduction of MHC-II immunoreactivity suggests an impairment in MHC-II linked antigen presenting cell expression.     

Histology, immunohistochemistry and ultrastructure of the tonsil of the soft palate of the horse

The tonsil of the soft palate was an oval, flat structure located centro-rostrally on the oral surface of the soft palate. Its stratified squamous non-keratinized epithelium was perforated by holes or small crypts the deeper parts of which were loosely spongiform inter-digitated with lymphoid tissue. These unusual features have not previously been reported in tonsils of any species. Crypts and reticulated epithelium as found in the lingual and palatine tonsils were not observed. Lectins showed varying affinities for specific layers of the epithelium. M cells were not observed. A few Langerhans cells were distributed among surface epithelial cells. Lymphoid tissue was arranged loosely and in isolated lymphoid follicles in the subepithelial lamina propria mucosae. Although IgA+ cells and macrophages were proportionately more numerous the amount of lymphoid tissue was much less than in the lingual and palatine tonsils. Most of the follicular germinal centres lacked a darkly stained corona. CD4 positive were more numerous than CD8+ lymphocytes and were distributed in the parafollicular and inter-follicular areas. Large clusters of mucus acini positive for glycogen, acidic and neutral mucopolysaccharides separated lymphoid tissue from deeply placed striated muscle. Only a few high endothelial venules were observed in the parafollicular and inter-follicular areas. These had relatively few vesiculo vacuolar or other organelles in their high endothelial cells and few lymphocytes attaching to their walls.     

Blood vessels within lymph nodes: a comparison between pigs and sheep

In sheep, most blood vessels enter the lymph nodes at a discrete hilus, which is where the capsule overlies medullary tissue. In pigs, vessels within the node arise from an extensive network of arteries on the surface, and most vessels penetrate the capsule where it overlies diffuse tissue--the counterpart of the sheep medulla. In both species the blood vessels divide extensively as they approach and supply the dense lymphoid tissue which contains lymph nodules. The blood vessels within sheep lymph nodules are surrounded by a thick layer of amorphous material. The dense lymphoid tissue has an abundant network of venules which have smooth muscle cells in their walls. These venules are involved in lymphocyte migration and in pigs they are lined by high endothelium which is similar to that in most other species, while in sheep the endothelium is much lower. Fenestrated capillaries occur in both pig and sheep lymph nodes.     

Cytochemical identification of lymphocytes and other mononuclear cells in ovine and bovine hemal nodes

Cytochemical and immunocytochemical studies were carried out with specific markers for B lymphocytes, dendritic reticulum cells (ATPase, 5'Nase, SIg) and T lymphocytes (ANAE, A.P.) in an attempt to identify the mononuclear cells present in bovine and ovine hemal nodes. The results show that primary nodes and mantle of secundary nodes are composed of B cells, whereas T cells are mainly localized in the interfollicular cords. Since such an arrangement resembles the picture in normal lymph nodes, but the direct contact between lymphatic tissue and blood is more reminiscent of the spleen, hemal nodes probably perform immunological functions similar to those of both normal lymph nodes and spleen.     

Histology and ultrastructure of the equine lingual tonsil. II. Lymphoid tissue and associated high endothelial venules

The stratified squamous epithelium of the lingual tonsil of five young horses was infiltrated with CD4 and CD8 positive cells, which were very numerous in the crypt reticular epithelium along with macrophages and IgGb and IgA positive cells. Lymphoid follicles of the lamina propria mucosae consisted of a parafollicular area, corona and germinal centre. The parafollicular area was populated by large numbers of CD4 and CD8 positive lymphocytes as well as macrophages, inter-digitating cells, and a few B-lymphocytes. The germinal centre contained mainly IgGb and IgG(T) positive cells, plasma cells and small numbers of follicular dendritic cells, macrophages, CD4, CD8 and IgA positive cells. Some venules in the parafollicular and inter-follicular areas had features characteristic of high endothelial venules with irregular nuclei and cytoplasmic processes on the luminal surface. In addition to the normal cytoplasmic organelles, a novel vesiculo-vacuolar organelle was observed in small clusters toward the lateral, luminal and abluminal surfaces of these high endothelial venules. These vesiculo organelles along with their stomata and diaphragms, communicated with each other and with inter-endothelial clefts forming a structural basis for enhanced permeability and extravasation of macromolecules. The presence of lymphocytes in the high endothelial venules is consistent with transmural and inter-endothelial passage of these cells.     

Oesophageal tonsil of the chicken

The oesophageal tonsil of the chicken is a novel member of the mucosal-associated lymphoid tissue (MALT), which is located around the entrance of the proventriculus. It consists of 6 to 8 single units, which are surrounded by a thin fibrous capsule. Each one is organised around the bottom of the longitudinal folds of the oesophagus, and serves as a 'tonsillar crypt'. Stratified squamous epithelium is infiltrated by lymphoid cells, i.e. T cells, plasma cells, macrophages, and dendritic cells, but not B cells, to form lymphoepithelium (LE). In the LE vimentin-, MHC II- and ATPase-positive cells possibly represent Langerhans' cells, but the appearance of 74.3 positive cells in the LE is unusual, because the 74.3 monoclonal antibody (mAb) recognises chicken follicular dendritic cells in the germinal centre and medulla of the bursal follicles. The subepithelial lymphoid tissue is organised into T- and B-dependent regions, which are the interfollicular areas and the germinal centres, respectively. Existence of high-endothelial venules in the interfollicular region suggests an extensive cellular connection between the oesophageal tonsil and the other lymphoid organs. In the resting oesophagus the lumen is closed, but during swallowing a bolus the crypt opens and the lymphoepithelium can be exposed to undigested food, antigens, infectious agents and vaccines. The location of the oesophageal tonsil, cranial to the stomach, may provide this organ with a unique role as compared to the other parts of the MALT; namely, it may contribute to the replication of infectious bursal disease virus (IBDV) and/or the pathogenesis of infectious bursal disease.     

First description and morphology of haemal nodes in piglets (Sus scrofa domestica)

In this study, the presence of haemal nodes, previously recognised especially in ruminants, was determined for the first time in piglets. The morphology of haemal nodes located in the abdominal cavity of seven piglets was studied by gross inspection and by histological methods. Haemal nodes reddish in colour and oval or round in shape were observed on the thin branches originating from the caudal and cranial mesenteric arteries. These nodes, having connection only with blood vessels, were covered with a thin connective tissue capsule. The haemal nodes had a hilus at the entrance of which large blood vessels were seen. These blood vessels extended into the inside of the nodes through trabeculae. Afferent and efferent lymph vessels were not observed in the haemal nodes. The nodes contained many sinuses formed by reticular fibres and reticular cells and filled by red blood cells. In the haemal nodes, lymphocytic infiltration was more commonly seen than lymph follicles.