Antigen delivery to gut associated lymphoid tissue of rabbits

A rabbit model was developed so that antigens, microbes or potential mucosal vaccines could be delivered in multiple doses directly to the luminal surface of the gut associated lymphoid tissue (GALT) located in the cecal appendix. A polyethylene catheter was implanted surgically into the tip of the appendix. It exited the body wall and progressed subcutaneously around the thorax to the dorsocervical region where it was attached to a subcutaneous obturator. The catheters were flushed every day with sterile saline. To assess patency of the system, radiographic contrast media was injected and the animals were radiographed. Rabbits were necropsied at 10, 30 and 60 days and tissues evaluated by histological, immunohistochemical and electron microscopic means. The microbial flora was evaluated also. All tissues examined were free of significant abnormalities. The advantage of this delivery system is its ability to provide multiple doses of immunogenic agents directly to a physiologically normal appendix over an extended period.     

Interstitial cells associated with the deep muscular plexus of the guinea-pig small intestine,with special reference to the interstitial cells of Cajal

Summary Interstitial cells associated with the deep muscular plexus of the guinea-pig small intestine were studied by electron microscopy, and three-dimensional cell models were reconstructed from serial ultrathin sections with a computer graphic system. Three types of cells were recognized. The first type was similar in shape to smooth muscle cells, but did not contain an organized contractile apparatus. Many large gap junctions comprising about 4% of the cell surface were present; they connected cells of the first type to each other, to the second type of cell and to smooth muscle cells of the outer circular layer. The second type of cell had a welldemarcated cell body with long slender processes and was characterized by a large amount of glycogen comprising about 9% of the cell volume. The third type of cell was similar to fibroblasts, and contained well-developed Golgi apparatus and rough endoplasmic retiulum. Some of these fibroblast-like cells (a possible subtype) formed small gap junctions. All three types of cells showed close relationships with nerve varicosities. This cellular network consisting of gap-junction-rich cells, glycogen-rich cells and smooth muscle cells may be involved in the pacemaking activity of intestinal movement.     

Fine structural study of interstitial cells associated with the deep muscular plexus of the rat small intestine,with special reference to the intestinal pacemaker cells

Two types of interstitial cells have been demonstrated in close association in the deep muscular plexus of rat small intestine, by electron microscopy. Cells of the first type are characterized by a fibroblastic ultrastructure, i.e. a well-developed granular endoplasmic reticulum, Golgi apparatus and absence of the basal lamina. They form a few small gap junctions with the circular muscle cells and show close contact with axon terminals containing many synaptic vesicles. They may play a role in conducting electrical signals in the muscle tissue. Cells of the second type are characterized by many large gap junctions that interconnect with each other and with the circular muscle cells. Their cytoplasm is rich in cell organells, including mitochondria, granular endoplasmic reticulum and Golgi apparatus. They show some resemblance to the smooth muscle cells and have an incomplete basal lamina, caveolae and subsurface cisterns. However, they do not contain an organized contractile apparatus, although many intermediate filaments are present in their processes. They also show close contacts with axon terminals containing synaptic vesicles. These gap-junction-rich cells may be regular components of the intestinal tract and may be involved in the pacemaking activity of intestinal movement.     

Microscopic anatomy of small-intestinal lymphoid patches in children and adults

Longitudinal histological sections of lymphoid patches (LP) in the small intestine, stained after van Gieson and with hematoxylin--eosin, obtained from 105 corpses of persons at the age of 0 up to 90 years have been studied. The LP parenchyma is presented as accumulation of lymphoid nodules++ with a germinative center, or without it and diffuse lymphoid tissue. The lymphoid nodules++ situate both in the mucous membrane and in the submucous tela of the small intestine. The area of the LP components in the newborns is the greatest--84% from the whole area of the LP section. During the human life it decreases and by the old age it makes 47%. The lymphoid nodules++ area with the germinative center in the newborns makes 21% from the area of the LP section, in children from 1 to 3 years of age it increases up to 50%, then it gradually decreases and in the elderly age it makes only 3.8%. The diffuse lymphoid tissue in the LP composition is revealed in all age periods. Size of the lymphoid nodules++ patches, situating in the jejunum and ileum walls in the newborns is the same. In children at the age of 10 days--12 years the LP nodules++ in the ileum are larger than those in the sejunum. The size of the LP noduli increase up to the period of the second childhood then decreases. The height of the lymphoid noduli in persons of mature, elderly and old ages decreases twice in comparison with the children of 3-12 years of age.     

Ageing combines CD4 T cell lymphopenia in secondary lymphoid organs and T cell accumulation in gut associated lymphoid tissue

Background

CD4 T cell lymphopenia is an important T cell defect associated to ageing. Higher susceptibility to infections, cancer, or autoimmune pathologies described in aged individuals is thought to partly rely on T cell lymphopenia. We hypothesize that such diverse effects may reflect anatomical heterogeneity of age related T cell lymphopenia. Indeed, no data are currently available on the impact of ageing on T cell pool recovered from gut associated lymphoid tissue (GALT), a crucial site of CD4 T cell accumulation.

Results

Primary, secondary and tertiary lymphoid organs of C57BL/6 animals were analysed at three intervals of ages: 2 to 6 months (young), 10 to 14 months (middle-aged) and 22 to 26 months (old). We confirmed that ageing preferentially impacted CD4 T cell compartment in secondary lymphoid organs. Importantly, a different picture emerged from gut associated mucosal sites: during ageing, CD4 T cell accumulation was progressively developing in colon and small intestine lamina propria and Peyer’s patches. Similar trend was also observed in middle-aged SJL/B6 F1 mice. Interestingly, an inverse correlation was detected between CD4 T cell numbers in secondary lymphoid organs and colonic lamina propria of C57BL/6 mice whereas no increase in proliferation rate of GALT CD4 T cells was detected. In contrast to GALT, no CD4 T cell accumulation was detected in lungs and liver in middle-aged animals. Finally, the concomitant accumulation of CD4 T cell in GALT and depletion in secondary lymphoid organs during ageing was detected both in male and female animals.

Conclusions

Our data thus demonstrate that T cell lymphopenia in secondary lymphoid organs currently associated to ageing is not sustained in gut or lung mucosa associated lymphoid tissues or non-lymphoid sites such as the liver. The inverse correlation between CD4 T cell numbers in secondary lymphoid organs and colonic lamina propria and the absence of overt proliferation in GALT suggest that marked CD4 T cell decay in secondary lymphoid organs during ageing reflect redistribution of CD4 T cells rather than generalized CD4 T cell decay. Such anatomical heterogeneity may provide an important rationale for the diversity of immune defects observed during ageing.

     

Ultrastructural observations of the tunica muscularis in the small intestine of Xenopus laevis, with special reference to the interstitial cells of Cajal

The distribution and ultrastructure of the interstitial cells of Cajal (ICC) has been examined in the small intestine of the frog Xenopus laevis, as the physiological significance of these cells remains obscure in amphibians and other lower vertebrates. The present study has revealed the existence of a special type of interstitial cell in the tunica muscularis of the small intestine of Xenopus; this cell is characterized by the presence of numerous caveolae, many small mitochondria, and the formation of intercellular connections with the same type of cell. Since these ultrastructural features are shared with mammalian ICC, the cells in the small intestine of Xenopus probably correspond to ICC. These cells also form close contacts with neighboring smooth muscle cells and with nerve varicosities containing accumulations of synaptic vesicles. These cellular networks are likely to be involved in the transmission of nerve impulses to muscle cells, as has been suggested for mammalian tissues. However, true gap junctions have not been detected; they occur neither between the same type of cells nor between the putative ICC and smooth muscle cells. The widespread distribution of ICC or equivalent cells in different groups of vertebrates, together with the conservation of their ultrastructural features, suggests that they differentiated early in vertebrate evolution to play key regulatory roles in gastrointestinal movement.     

Observations on the dental anatomy of piranhas (Characidae) with special reference to tooth structure

A study of the tissues of the teeth and jaws in piranhas, using the scanning electron microscope and various techniques of light microscopy, revealed many dental adaptations related to the specialized feeding habits of these carnivorous fishes. The dentition is primarily sectorial, although some anterior teeth may be used in grasping. The scissor-like rows of teeth are maintained by the specialized pattern of tooth replacement. The bones of the jaws and the tooth attachment support the teeth very firmly. In its structural organization, the enameloid covering the teeth closely resembles that on the sectorial teeth of sharks and is adapted to the probable stress patterns set up in biting.     

Immunocytochemical detection of Ig-positive cells in blood, lymphoid organs and the gut associated lymphoid tissue of the turbot (Scophthalmus maximus)

The present study was designed to search for the sites of the B-cell lineage in the different lymphoid organs of turbot (Scophthalmus maximus) by immunoperoxidase staining with a rabbit polyclonal antiserum against deglycosylated turbot IgM (TUDG-6). A turbot immunoglobulin (Ig) fraction, isolated by protein A, was checked for purity by gel filtration and SDS-PAGE under reducing conditions. The turbot IgM was deglycosylated and used to raise an antiserum. The antiserum titre was evaluated in ELISA. It was then used to analyse turbot peripheral blood leucocytes for membrane and cytoplasmic Ig and for immunohistochemistry with turbot lymphoid tissues. Very low numbers of Ig+ cells were found in thymus sections. In sections of spleen, Ig+ cells were observed in white pulp, around ellipsoids but were mostly concentrated and associated with melanomacrophage centers (MMCs). The lymphoid Ig+ cells in the kidney tended to be dispersed among haematopoietic and granulopoietic cell populations and were in intimate association with the MMCs and blood vessels. This association between MMCs and Ig+ cells in the spleen and the kidney, is discussed with respect to the role played by these organs in the immune system of fish. Last, the lymphoid population in the gut associated lymphoid tissue (GALT) of turbot was characterised with respect to staining for Ig. Immunoreactive cells were rarely detected in the epithelial layer although many lymphocytes were present, but they were frequently observed in the lamina propria, presumably as part of the GALT and involved in mucosal immune responses.