Developmental characteristics of aggregated lymphoid nodules area in the abomasum of fetal Bactrian camels (Camelus bactrianus).

BACKGROUND: Bactrian camel is one of the important economic animals in northwest China. They live in arid desert, and their gestation period is about 13 months, which is longer than other ruminants (such as cattle and sheep). The harsh living conditions have made its unique histological characteristics a research focus. Aggregated lymphoid nodules area (ALNA) in the abomasum of Bactrian camels, as one of the most important sites for the induction of the immune response, provide a comprehensive and effective protective role for the organism, and their lack of information will affect the feeding management, reproduction and epidemic prevention of Bactrian camels. In this study, the histological characteristics of the fetal ALNA in the abomasum of Bactrian camels at different developmental gestation have been described by using light microscopy and histology . RESULTS: The ALNA in the abomasum of the Chinese Alashan Bactrian camel is a special immune structure that was first discovered and reported by Wen-hui Wang. To further establish the developmental characteristics of this special structure in the embryonic stage, the abomasum ALNA of 8 fetuses of Alashan Bactrian camels with different gestational ages (5~13 months) were observed and studied by anatomy and histology. The results showed that the aggregation of reticular epithelial cells (RECs) surrounded by a very small number of lymphoid cells was detected for the first time in the abomasum of fetal camel at 5 months gestation, which was presumed to be primitive ALNA. At 7 months gestation, the reticular mucosal folds region (RMFR) appeared, but the longitudinal mucosal folds region (LMFR) was not significant, and histological observations showed that there were diffusely distributed lymphocytes around the RECs. At 10months gestation, RMFR and LMFR were clearly visible, lymphoid follicles appeared in histological observation, lymphocytes proliferated vigorously. By 13 months, the volume of lymphoid follicles increased, forming the subepithelial dome (SED), and there was a primitive interfollicular area between the lymphoid follicles, which contained high endothelial vein (HEV), but no germinal center (GC) was found. In summary, ALNA of Bactrian camels is not fully mature before birth. CONCLUSIONS: Generally, the small intestine PPs of ruminants (such as cattle and sheep) is already mature before birth, while the ALNA in the abomasum of Bactrian camels is not yet mature in the fetal period. During the development of ALNA in Bactrian camel, the development of lymphoid follicles extends from submucosa to Lamina propria. Interestingly, the deformation of FAE changes with age from simple columnar epithelium at the beginning of pregnancy to Simple cuboidal epithelium, which is opposite to the FAE deformation characteristics of PPs in the small intestine of fetal cattle and sheep. These results are the basis of further research on the specificity of ALNA in the abomasum of Bactrian camels.

Anatomy of teleost fish immune structures and organs.

The function of a tissue is determined by its construction and cellular composition. The action of different genes can thus only be understood properly when seen in the context of the environment in which they are expressed and function. We now experience a renaissance in morphological research in fish, not only because, surprisingly enough, large structures have remained un-described until recently, but also because improved methods for studying morphological characteristics in combination with expression analysis are at hand. In this review, we address anatomical features of teleost immune tissues. There are approximately 30,000 known teleost fish species and only a minor portion of them have been studied. We aim our review at the Atlantic salmon (Salmo salar) and other salmonids, but when applicable, we also present information from other species. Our focus is the anatomy of the kidney, thymus, spleen, the interbranchial lymphoid tissue (ILT), the newly discovered salmonid cloacal bursa and the naso-pharynx associated lymphoid tissue (NALT).

Role of Lymphoid Structure in Skin Immunity.

The skin is the outermost organ of the body and is exposed to many kinds of external pathogens. To manage this, the skin contains multiple types of immune cells. To achieve sufficient induction of cutaneous adaptive immune responses, the antigen presentation/recognition in the skin is an essential process. Recent studies have expanded our knowledge of how T cells survey their cognate antigens in the skin. In addition, the formation of a lymphoid cluster, named inducible skin-associated lymphoid tissue (iSALT), has been reported during skin inflammation. Although iSALT may not be classified as a typical tertiary lymphoid organ, it provides specific antigen presentation sites in the skin. In this article, we provide an overview of the antigen presentation mechanism in the skin, with a focus on the development of iSALT and its function.

Graph-based description of tertiary lymphoid organs at single-cell level.

Our aim is to complement observer-dependent approaches of immune cell evaluation in microscopy images with reproducible measures for spatial composition of lymphocytic infiltrates. Analyzing such patterns of inflammation is becoming increasingly important for therapeutic decisions, for example in transplantation medicine or cancer immunology. We developed a graph-based assessment of lymphocyte clustering in full whole slide images. Based on cell coordinates detected in the full image, a Delaunay triangulation and distance criteria are used to build neighborhood graphs. The composition of nodes and edges are used for classification, e.g. using a support vector machine. We describe the variability of these infiltrates on CD3/CD20 duplex staining in renal biopsies of long-term functioning allografts, in breast cancer cases, and in lung tissue of cystic fibrosis patients. The assessment includes automated cell detection, identification of regions of interest, and classification of lymphocytic clusters according to their degree of organization. We propose a neighborhood feature which considers the occurrence of edges with a certain type in the graph to distinguish between phenotypically different immune infiltrates. Our work addresses a medical need and provides a scalable framework that can be easily adjusted to the requirements of different research questions.

A teleost structural analogue to the avian bursa of Fabricius.

The bursa of Fabricius is a primary and secondary lymphoid organ considered exclusively present in birds, and studies of this structure have been vital to our current understanding of the adaptive immune system of vertebrates. In this study, we reveal substantial lymphoepithelial tissue in a previously undescribed bursa in Atlantic salmon (Salmo salar), situated caudal to the urogenital papilla of the cloaca and thus analogous to the anatomical placement of the bursa of Fabricius. We investigated three groups of Atlantic salmon at different maturational stages and characterized the structure by applying dissection, radiology, scanning electron microscopy and histological techniques, including immunohistochemistry and in situ hybridization. We found that the epithelial anlage of the salmon cloacal bursa developed into substantial lymphoepithelial tissue and subsequently regressed following sexual maturation. Such a dynamic development is also a key characteristic of the avian bursa. The presence of intraepithelial lymphocytes was concomitant with expression of the leukocyte-attracting chemokine CCL19, indicative of lymphoid organ functions. We did not observe recombination or gene conversion in salmon bursal lymphocytes at any developmental stage, indicating the absence of primary lymphoid organ functions in contrast to the bursa of Fabricius. However, the possibility of the bursa to trap both enteric and environmental antigens, combined with the presence of several antigen-presenting cells residing within the lymphoepithelium, suggest the structure has secondary lymphoid organ functions. We present the discovery of a lymphoid organ in Atlantic salmon with striking topographical similarities to that of the bursa of Fabricius in birds. In addition, the age-dependent dynamics of its lymphoepithelium suggest functions related to the maturation processes of lymphocytes.

Comparative study of cartilaginous fish divulges insights into the early evolution of primary, secondary and mucosal lymphoid tissue architecture.

Cartilaginous fish are located at a pivotal point in phylogeny where the adaptive immune system begins to resemble that of other, more-derived jawed vertebrates, including mammals. For this reason, sharks and other cartilaginous fish are ideal models for studying the natural history of immunity. Insights from such studies may include distinguishing the (evolutionarily conserved) fundamental aspects of adaptive immunity from the (more recent) accessory. Some lymphoid tissues of sharks, including the thymus and spleen, resemble those of mammals in both appearance and function. The cartilaginous skeleton of sharks has no bone marrow, which is also absent in bony fish despite calcified bone, but cartilaginous fish have other Leydig's and epigonal organs that function to provide hematopoiesis analogous to mammalian bone marrow. Conserved across all vertebrate phylogeny in some form is gut-associated lymphoid tissues, or GALT, which is seen from agnathans to mammals. Though it takes many forms, from typhlosole in lamprey to Peyer's patches in mammals, the GALT serves as a site of antigen concentration and exposure to lymphocytes in the digestive tract. Though more complex lymphoid organs are not present in agnathans, they have several primitive tissues, such as the thymoid and supraneural body, that appear to serve their variable lymphocyte receptor-based adaptive immune system. There are several similarities between the adaptive immune structures in cartilaginous and bony fish, such as the thymus and spleen, but there are mechanisms employed in bony fish that in some instances bridge their adaptive immune systems to that of tetrapods. This review summarizes what we know of lymphoid tissues in cartilaginous fishes and uses these data to compare primary and secondary tissues in jawless, cartilaginous, and bony fishes to contextualize the early natural history of vertebrate mucosal immune tissues.

Nonproliferative and Proliferative Lesions of the Rat and Mouse Hematolymphoid System.

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative changes in rats and mice. The purpose of this publication is to provide a standardized nomenclature for classifying changes observed in the hematolymphoid organs, including the bone marrow, thymus, spleen, lymph nodes, mucosa-associated lymphoid tissues, and other lymphoid tissues (serosa-associated lymphoid clusters and tertiary lymphoid structures) with color photomicrographs illustrating examples of the lesions. Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. The nomenclature for these organs is divided into 3 terminologies: descriptive, conventional, and enhanced. Three terms are listed for each diagnosis. The rationale for this approach and guidance for its application to toxicologic pathology are described in detail below.

NKT Cell Hyporesponsiveness Leads to Unrestrained Accumulation of Marginal Zone B Cells in Hypercholesterolemic Apolipoprotein E-Deficient Mice.

Recently, the role of B cells in atherosclerosis has gained more attention but studies have mainly focused on B1 and follicular B cell subsets. Therefore, the contribution of marginal zone (MZ) B cells in experimental atherosclerosis remains elusive. In the current study, we examined the MZ B cell compartment in atherosclerotic apoE-deficient (apoE-/-) mice and found that hypercholesterolemia in these mice was associated with an increased number and percentage of MZ B cells. This aberrant accumulation of MZ B cells was not associated with alterations in their development or increased proliferation but was due to decreased apoptotic cell death. This decrease in MZ B cell death in apoE-/- mice was associated with the reduced capacity of invariant NKT (iNKT) cells to produce IFN-γ and IL-4 after activation. Lowering cholesterol plasma levels with ezetimibe in apoE-/- mice reversed iNKT function and MZ B cell accumulation. To elucidate the mechanism whereby iNKT cells control MZ B cell accumulation in apoE-/- mice, we performed an adoptive transfer of iNKT cells and found that only wild-type iNKT cells but not IFN-γ-/- iNKT cells reversed MZ B cell accumulation in apoE-/- recipient mice. Our findings reveal that lipid changes associated with atherosclerotic disease induce decreased production of IFN-γ by iNKT, which in turn leads to aberrant accumulation of MZ B cells. This study further extends the importance of iNKT cells in regulating MZ B cell compartment.

Understanding the anatomic basis for obstructive sleep apnea syndrome in adolescents.

RATIONALE: Structural risk factors for obstructive sleep apnea syndrome (OSAS) in adolescents have not been well characterized. Because many adolescents with OSAS are obese, we hypothesized that the anatomic OSAS risk factors would be more similar to those in adults than those in children. OBJECTIVES: To investigate the anatomic risk factors in adolescents with OSAS compared with obese and lean control subjects using magnetic resonance imaging (MRI). METHODS: Three groups of adolescents (age range: 12-16 yr) underwent MRI: obese individuals with OSAS (n = 49), obese control subjects (n = 38), and lean control subjects (n = 50). MEASUREMENTS AND MAIN RESULTS: We studied 137 subjects and found that (1) obese adolescents with OSAS had increased adenotonsillar tissue compared with obese and lean control subjects; (2) obese OSAS adolescents had a smaller nasopharyngeal airway than control subjects; (3) the size of other upper airway soft tissue structures (volume of the tongue, parapharyngeal fat pads, lateral walls, and soft palate) was similar between subjects with OSAS and obese control subjects; (4) although there were no major craniofacial abnormalities in most of the adolescents with OSAS, the ratio of soft tissue to craniofacial space surrounding the airway was increased; and (5) there were sex differences in the pattern of lymphoid proliferation. CONCLUSIONS: Increased size of the pharyngeal lymphoid tissue, rather than enlargement of the upper airway soft tissue structures, is the primary anatomic risk factor for OSAS in obese adolescents. These results are important for clinical decision making and suggest that adenotonsillectomy should be considered as the initial treatment for OSAS in obese adolescents, a group that has poor continuous positive airway pressure adherence and difficulty in achieving weight loss.

Porin differentiates TLR mediated proinflammatory response of follicular zone B cell from TLR-unresponsive IL-10 expressing marginal zone B cell.

TLR-ligands are frequently chosen as candidates for vaccine or adjuvant development because they can primarily bridge innate signaling with adaptive immune responses. Since the adjuvant action of porin, the major outer membrane protein commonly present on Gram-negative bacteria, has been tested on several antigen-presenting cells, we investigated its role in driving systemic immunity which is considered a benchmark for a successful adjuvant. Here, we show porin differentially regulated splenic marginal zone (MZ) and follicular zone (FO) B cell responses in contrast to other classical TLR2-ligands FSL-1 and Pam3CSK4. The protein up-regulated TLR2 and TLR6 and stimulated the activation and costimulatory molecules on FO B cells skewing the cells toward TLR-dependent type-1 cytokine response. However, porin could not up-regulate the TLRs and activate MZ B cells. These cells responded to porin by expressing toll-interacting protein (TOLLIP), the TLR2 and -4 signaling inhibitor along with stimulation of the intracellular pathogen recognition receptor NLR caspase recruitment domain containing protein 5 (NLRC5). The CD1d(hi) MZ B cells released IL-10 unequivocally demonstrating regulatory B cell feature. Immunization with porin also resulted in transient IL-10 expression by the CD19(+)CD21(hi) B cells prior to plasma cell formation. Moreover, the plasma cells developed from the B-2 cell subsets show marked variation in generation of immunoglobulin subclasses. The work delineates multi-faceted role of B cell subsets induced by porin for robust immunity without compromising with the checks and controls.

Anatomical basis of tolerance and immunity to intestinal antigens.

The intestinal immune system has to discriminate between harmful and beneficial antigens. Although strong protective immunity is essential to prevent invasion by pathogens, equivalent responses against dietary proteins or commensal bacteria can lead to chronic disease. These responses are normally prevented by a complex interplay of regulatory mechanisms. This article reviews the unique aspects of the local microenvironment of the intestinal immune system and discuss how these promote the development of regulatory responses that ensure the maintenance of homeostasis in the gut.

Diameter of the lymphoid follicles in the vermiform appendix of Bangladeshi cadaver.

Appendicitis is the most common clinical condition of the appendix. Many cases of acute appendicitis result from obstruction of the lumen of the appendix by lymphoid hyperplasia. The vermiform appendix is a worm-like, closed-ended, narrow, small tubular structure, projecting from posteromedial wall of cecum. It is an integral part of the Gut Associated Lymphoid Tissue (GALT) system. The lymphoid follicles of the vermiform appendix vary in respect to their number, diameter and location in different ages. This study was done to measure and establish the normal diameter with age related variation of the lymphoid follicles of vermiform appendix in Bangladeshi population. This descriptive cross sectional study was carried out in the Department of Anatomy, Sir Salimullah Medical College, Dhaka, from January 2008 to June 2009. Sixty (60) postmortem vermiform appendices of different age groups of Bangladeshi cadavers. For studying the diameter of lymphoid follicles in the vermiform appendix in relation to age, the collected samples were divided into five groups namely Group-A between age ranges 0-20 years, Group-B between age ranges 21-30 years, Group-C between age ranges 31-40 years, Group-D 41-50 years and Group-E age above 50 years. From each age group, six (6) fresh samples were selected for histological study. From each vermiform appendix three slides were prepared each from its base, middle part and near the tip and were stained with routine H & E stain. The normal diameter of the follicles of the vermiform appendix ranged from 0.40 mm to 0.66 mm. The highest average group diameter was 0.62±1.10mm in Group-A and the lowest value was 0.45±2.73mm in Group-E. It was obvious that the diameter decreased gradually with advancing age. The average normal diameter of the lymphoid follicles per histological section of vermiform appendix reduced with advancing age and showed a significant negative correlation with age (p<0.001). In the present study, the normal diameter of the lymphoid follicles of the vermiform appendix reduced significantly with advancing age.

Immunohistochemistry of the nasal cavity-associated lymphoid tissue in the dolphin (Stenella coeruleoalba, Meyen 1833).

The striped dolphin (Stenella coeruleoalba) is a medium-sized pelagic dolphin with a single external nasal opening (blowhole) located in the rostral and dorsal regions of the skull. The nasal cavity is divided into three sections: the olfactory, respiratory, and vestibular areas. The surface epithelium lining the regio vestibularis is the first tissue in the nose to be directly affected by environmental antigens. Cetaceans have a significant amount of mucosa-associated lymphoid tissue (MALT) located throughout their bodies. The lymphoid tissue found in the nasal mucosa is known as nose- or nasopharynx-associated lymphoid tissue (NALT). NALT has not yet been studied in dolphins, but it has been identified and documented in humans and laboratory rodents. This study utilized toll-like receptor 2 (TLR2), CD4, Langerin/CD207, and inducible nitric oxide synthase to characterize, for the first time, immune cells in the mucosal regio vestibularis of the S. coeruleoalba nasal cavity using confocal microscopy immunofluorescence techniques. The findings revealed scattered immune cells immunoreactive to the tested antibodies, present in both the epithelial tissue lining the nasal cavity vestibulum and the underlying connective tissue. This study enhances our comprehension of the immune system of cetaceans. RESEARCH HIGHLIGHTS: This study provides new insights into NALT in S. coeruleoalba. This research deepens the knowledge of the skin of cetaceans.

Morphology of the ligament of Treitz likely depends on its fetal topographical relationship with the left adrenal gland and liver caudate lobe as well as the developing lymphatic tissues: a histological study using human fetuses.

To investigate the factors affecting the development of the ligament of Treitz, we examined sagittal and frontal histological sections of 35 human fetuses with a crown-rump length of 100-300 mm (approximately 16-38 weeks of gestation). The retropancreatic fascia consistently extended in a layer behind the pancreatic body and the splenic artery and vein, and also in front of the left renal vein and left adrenal. In 18 specimens, a connective tissue band was seen originating from the diaphragmatic crus around the esophageal opening and ending at the retropancreatic fascia to the left of the origin of the celiac artery. In 10 of these 18 specimens, these putative upper parts of the ligament contained striated muscles, or so-called Hilfsmuskel. Although most of other 17 specimens were larger fetuses, the left adrenal, the liver caudate lobe and the celiac ganglion made space for the ligament very limited. In 22 specimens including the above 18, the retropancreatic fascia extended inferiorly to approach the fourth portion of the duodenum (D4) or the duodenojejunal junction (DJJ). However, in 11 of the 22 examples of the putative lower part of the ligament, the connection between the duodenal muscle coat and the fascia was interrupted by developing lymphatic tissues. Consequently, the ligament of Treitz seemed to develop from both pleuroperitoneal membrane-derived cells and the retropancreatic fusion fascia, although the morphology was markedly modified by adjacent structures such as the adrenal gland. The ligament may "recover" after the adrenal becomes reduced in size after birth.

Histomorphological study of germinal centre of vermiform appendix in Bangladeshi cadaver.

The study was done to find out the number of germinal centre in human vermiform appendix of Bangladeshi people to magnify the knowledge regarding the diverse number of germinal centre of human vermiform appendix in our population in the department of Anatomy, Mymensingh Medical College, Bangladesh from July 2006 to June 2007. Total 40 appendices were collected for histological study of different age and sex during postmortem examination in the autopsy laboratory of department of Forensic Medicine, Mymensingh Medical College. This cross sectional study was done by convenient sampling technique. For convenience of differentiating the changes in number of germinal centre of vermiform appendix in relation to age and sex, findings were classified in four groups, Group A up to 20 years, Group B 21-35 years, Group C 36-55 years and Group D 56-70 years. In the present study the number of germinal centre was highest in Group B (52.38%) but in Group D it was nil. Here mean number of germinal centre in male (1.05) were more than in female (0.8).

Protective effects of zinc-bearing clinoptilolite on broilers challenged with Salmonella pullorum.

This study was conducted to evaluate the effects of zinc-bearing clinoptilolite (ZnCP) on broilers challenged with Salmonella pullorum for a 21-d feeding trial. A total of 240 one-day-old chickens was allocated into 4 treatment groups: 1) nonchallenged control (CON) fed basal diet; 2) S. pullorum-challenged control (SCC) fed basal diet; 3) Salmonella challenge fed basal diet plus antibiotic (ANT); 4) Salmonella challenge fed basal diet plus 0.2% ZnCP (ZnCP). Compared with CON, Salmonella challenge caused adverse effects on ADG (P<0.05), ADFI, feed/gain ratio in broilers, Salmonella and Lactobacillus colonies at 7 d (P<0.05) and 21 d, and serum diamine oxidase (DAO) activity. Moreover, the relative weight of spleen of 21-d birds, malondialdehyde (MDA) content of jejunual and ileal mucosa at 21 d, and the superoxide dismutase (SOD) activity of ileal mucosa were also significantly negatively affected by SCC treatment (P<0.05). Supplementation of ZnCP in basal diet significantly improved ADG and reduced Salmonella colonies in cecal contents and serum DAO activity both at 7 and 21 d (P<0.05), compared with SCC. Furthermore, supplementation with ZnCP as well as ANT significantly decreased the relative weight of spleen at 21 d, reduced MDA contents of jejunual and ileal mucosa at 21 d (P<0.05), and improved the SOD activity of ileal mucosa at 7 d as compared with SCC (P<0.05). The results suggested that ZnCP addition in feed exerted protective effects on performance and gut health of broilers against S. pullorum infection.

[Functional morphology of conjunctive tissue stroma of spleen in the age aspect].

The article presents the data on the structural and functional changes of conjunctive tissue of the spleen in postnatal ontogenesis of a person. The study was performed on 125 cadaveric spleens of the people of both sexes, who died from traumas and diseases not causing pathologic changes in the spleen. Definition of ontogenetic phases and chronological confines of age periods was identified according to Bunak V. V. (1965). The measurement of linear dimensions and mass of organ, histological, histochemical study and morphometry were performed. According to factual evidence, at the age from birth to 4 years the content of lymphatic follicles increases against a background of decrease of conjunctive tissue component and red pulp in the area of spleen section. By 8 or 10 years the part of lymphoid tissue decreases, but the part of conjunctive tissue and red pulp increases. Ageing symptoms are revealed at the age of 18, the increase of volume of conjunctive tissue component and destruction of external elastic membrane of trabecular artery of spleen take place. The destruction of elastic and reticulin fibers of soft skeleton, reduction of cellular elements (cells, fibroblasts and fibrocytes) and conjunctive tissue stroma collagenization are observed at a mature and old age.

Investigating mammary glands of lactating goats for the presence of tertiary lymphoid organs.

Ectopic tertiary lymphoid organs (TLOs) have been identified in many organs, such as the lungs, nasal cavities, and kidneys of both mice and humans. Although lymphocyte aggregates have been observed in the mammary glands of ruminants, the details remain unclear. In this study, we investigated the mammary glands of lactating goats for the presence of TLOs. The localization of CD20 (B cells), CD3 (T cells), MECA79 (high endothelial venules), CD40 (follicular dendritic cells), BCL6 (germinal center), and IgA was examined by immunohistochemistry. The concentrations of IgG, IgA, lactoferrin, ß-defensin-1, cathelicidin-2, cathelicidin-7, S100A7, and S100A8 in milk were measured by ELISA. The localization and amount of tight junction (TJ) proteins (claudin-3 and claudin-4) were examined using immunofluorescence and western blotting. We found that 19 out of 30 udders contained lymphocyte aggregates, which showed positive reactions against CD20, CD3, CD40, and MECA79. In addition, large-sized aggregations showed separate localization of B cells and T cells and a positive reaction against BCL6, although BCL6 was sparsely localized in the aggregations. These results indicate that mammary glands of lactating goats contain TLOs. The IgG and IgA concentrations in the milk of TLO-positive goats and the number of IgA-positive cells were higher than those in negative goats. Furthermore, claudin-4 was localized in the TJ region and the amount was higher in TLO-positive mammary glands than that in the negative group, indicating the presence of leakages at TJs. In conclusion, a majority of lactating goat udders have TLOs, which contribute to local immunity by producing immunoglobulins.

Distribution, organization and innervation of gastric MALT in conventional piglet.

Mucosa-associated lymphoid tissue (MALT) is the initial inductive site for mucosal immunity. It is present in the different layers of the mucosal wall and consists of organized lymphoid tissue which may occur as isolated or aggregated lymphoid follicles (LFs) and interfollicular areas. It is present in many organs, including the pig stomach. Gastric MALT has been intensely studied in experimentally infected pigs but few data are available in healthy, non-gnotobiotic or germ-free animals. In the present study we described the gastric MALT in conventional piglets in the cardiac mucosa of the gastric diverticulum, in the pyloric mucosa, and in the sites of transition from cardiac to oxyntic and from cardiac to pyloric mucosa by means of histological and immunohistochemical stains. The majority of LFs were located in the cardiac mucosa and in the transition from the cardiac to the oxyntic mucosa. Here the LFs were mainly located in the submucosa and reached the mucosa; we called these submucosal lymphoid follicles (SLFs). In the pyloric mucosa and in the transition sites from the cardiac to the pyloric mucosa, LFs were located in the mucosa; we called these mucosal lymphoid follicles (MLFs). In SLFs, a compartmental organization of T and B lymphocytes was present; by contrast, in the MLFs, the T and B cells were intermingled, suggesting the possibility of different roles for the two types of follicles. In the epithelium overlying the lymphoid tissue, numerous T lymphocytes and some cells immunoreactive to cytokeratin-18 were observed. Following the application of the fluorescent tracer DiI into the SLFs of the diverticulum, enteric neurones located in the submucosal plexus were labelled, confirming the interplay between the immune and the enteric nervous system.

Lymphoid follicle destruction and immunosuppression after repeated CpG oligodeoxynucleotide administration.

DNA containing unmethylated cytidyl guanosyl (CpG) sequences, which are underrepresented in mammalian genomes but prevalent in prokaryotes, is endocytosed by cells of the innate immune system, including macrophages, monocytes and dendritic cells, and activates a pathway involving Toll-like receptor-9 (TLR9). CpG-containing oligodeoxynucleotides (CpG-ODN) are potent stimulators of innate immunity, and are currently being tested as adjuvants of antimicrobial, antiallergic, anticancer and antiprion immunotherapy. Little is known, however, about the consequences of repeated CpG-ODN administration, which is advocated for some of these applications. Here we report that daily injection of 60 microg CpG-ODN dramatically alters the morphology and functionality of mouse lymphoid organs. By day 7, lymphoid follicles were poorly defined; follicular dendritic cells (FDC) and germinal center B lymphocytes were suppressed. Accordingly, CpG-ODN treatment for > or =7 d strongly reduced primary humoral immune responses and immunoglobulin class switching. By day 20, mice developed multifocal liver necrosis and hemorrhagic ascites. All untoward effects were strictly dependent on CpG and TLR9, as neither the CpG-ODN treatment of Tlr9(-/-) mice nor the repetitive challenge of wild-type mice with nonstimulatory ODN (AT-ODN) or with the TLR3 agonist polyinosinic:cytidylic acid (polyI:C) were immunotoxic or hepatotoxic.