Appendectomy, tonsillectomy, and risk for sarcoidosis - A hospital-based case-control study in Japan

BACKGROUND

The role of surgery in the onset of sarcoidosis is unclear. We investigated whether surgery is an internal environmental factor for sarcoidosis onset within the Japanese population.

METHODS

We enrolled 222 patients diagnosed with sarcoidosis (78 men, 144 women) who were admitted to our department between 1984 and 2012. We also enrolled 529 control subjects (251 men, 278 women), who were matched for sex, age at admission, and year of admission. Surgical history, family history, and smoking status were evaluated.

RESULTS

Multivariate analysis correlated history of appendectomy (OR, 1.55; 95% CI, 1.05-2.29) and tonsillectomy (OR, 2.79; 95% CI, 0.91-8.56) with the occurrence of sarcoidosis; other surgical procedures had no correlation. In women, appendectomy had a stronger association with sarcoidosis (OR, 1.69; 95% CI, 1.05-2.73), as opposed to that in men (OR, 1.39; 95% CI, 0.68-2.85). This association was greater in women aged ≥45 years than in those aged <45 years. There was a stronger correlation between tonsillectomy and sarcoidosis in women (OR, 3.30; 95% CI, 0.88-12.39), than in men (OR, 1.26; 95% CI, 0.10-16.52). ORs for sarcoidosis were 5.55 (95% CI, 2.02-15.27) and 0.97 (95% CI, 0.52-1.84) in women aged ≥45 years with a history of appendectomy at <20 years and ≥20 years, respectively, with the former being statistically significant.

CONCLUSIONS

Appendix and tonsil removal was associated with sarcoidosis onset, suggesting their potential protective role against sarcoidosis development. Further studies are needed to minimize possible confounding factors.

Intestinal stem cells and intestinal homeostasis in health and in inflammation: A review

BACKGROUND

The human intestine is a complex group of organs, highly specialized in processing food and providing nutrients to the body. It is under constant threat from microbials and toxins and has therefore developed a number of protective mechanisms. One important mechanism is the constant shedding of epithelial cells into the lumen; another is the production and maintenance of a double-layered mucous boundary in which there is continuous sampling of the luminal microbiota and a persistent presence of antimicrobial enzymes. However, the gut needs commensal bacteria to effectively break down food into absorbable nutrients, which necessitates constant communication between the luminal bacteria and the intestinal immune cells in homeostasis. Disruption of homeostasis, for whatever reason, will give rise to (chronic) inflammation.

DISCUSSION

Both medical and surgical management of this disruption is discussed.

[DYNAMICS OF INDICES OF A LOCAL IMMUNITY IN AN ACUTE APPENDICITIS]

Abstract The results of investigation on dynamics of a local immunity indices in an acute appendicitis, depending on the pathological process stage as well as on bacteriological investigation of parietal microflora of processus vermicularis, were adduced. The sIgA and lisocymal dynamics have witnessed that while a destructive process progressing their concentration was enhanced, and in a gangrenous acute appendicitis they practically disappeared. Due to affection of a barrier function of the processus vermicularis wall a favorable conditions were created for the microorganisms intramural translocation as well as to abdominal cavity.

Role of Eosinophils in Acute Appendicitis

INTRODUCTION

High negative appendectomy rate still prevails on conventional histologic examination. Increased mural eosinophilic infiltrate had been observed in acute appendicitis. Present study aimed to evaluate the role of mural eosinophils in clinically suspected acute appendicitis but histological normal appendix, as an indicator of acute inflammation, alone or in association with edema and to estimate the cut off value for high eosinophil count for the diagnosis of acute appendicitis.

METHODS

A prospective cross sectional study was conducted on appendectomy specimens which were categorized into three groups of classical acute appendicitis, negative appendectomy and control. HandE and Giemsa stained section were studied for the presence of mural eosinophilic infiltrate, mast cells and edema.

RESULTS

Of total 170 cases, group 1 comprised of 68 cases, group 2 consisted of 78 cases and group 3 consisted of 24 cases. Mean eosinophil and mast cell counts in the muscularis propria were significantly higher in CAA and NA categories when compared to control group. Positive association was found between high eosinophil count and edema in CAA and NA categories. Cut off value of ≥6/ mm2 for mural eosinophil count was not significantly different in between NA and control categories.

CONCLUSIONS

Increased mural eosinophils were significantly present in acute appendicitis and clinically suspected acute appendicitis but histological normal appendix when compared with control group. Sole presence of increased mural eosinophils might represent acute inflammation. However, cut off value for high eosinophil count could not be established to suggest acute appendicitis.

Is CD19 an immunological diagnostic marker for acute appendicitis?

BACKGROUND

The appendix is considered as part of the gut-associated lymphoid tissue; however, lymphocyte subsets in this tissue are not fully defined.

OBJECTIVE

To investigate and compare the function and phenotype of lymphocyte subsets in peripheral blood and appendix of patients with normal and inflamed appendix tissues.

METHODS

Peripheral blood samples and appendiceal mononuclear cells were obtained from 81 patients (mean age; 23 ± 10.5 years), clinically suspected of having appendicitis. The phenotypic characteristics of lymphocyte subsets in peripheral blood (before and 48-72 hrs after appendectomy) and in appendix tissue were analyzed by three color-flow cytometry. The proliferative response of mononuclear cells was assessed by MTT method.

RESULTS

The frequency of CD19+DR+, HLA-DR+ and CD19+ cells in the appendix tissue were significantly higher than that of the peripheral blood in all the groups (p<0.001). The percentage of CD19+ cells and HLA-DR+CD19+ cells significantly decreased after appendectomy in the peripheral blood of the patients with acute appendicitis (p=0.047 and p=0.03, respectively). CD19 and HLA-DR plus CD19 had better diagnostic efficiency compared with T cell markers (area under the ROC curve [AUC]= 0.76 and 0.73, respectively).

CONCLUSION

These results indicate a significant difference in CD19+ and HLA-DR+ lymphocytes between peripheral blood and the appendix tissue.

Appendectomy and Clostridium difficile colitis: Relationships revealed by clinical observations and immunology

Advances in understanding the interaction between the human immune system and the microbiome have led to an improved understanding of the function of the vermiform appendix as a safe-house for beneficial bacteria in the colon. These advances have been made despite long standing clinical observations that the appendectomy is a safe and effective procedure. However, more recent clinical data show that an appendectomy puts patients at increased risk for recurrent Clostridium difficile (C. difficile)-associated colitis, and probably other diseases associated with an altered microbiome. At the same time, appendectomy does not apparently put patients at risk for an initial onset of C. difficile-associated colitis. These clinical observations point toward the idea that the vermiform appendix might not effectively protect the microbiome in the face of broad spectrum antibiotics, the use of which precedes the initial onset of C. difficile-associated colitis. Further, these observations point to the idea that historically important threats to the microbiome such as infectious gastrointestinal pathogens have been supplanted by other threats, particularly the use of broad spectrum antibiotics.

Does a decrease of NK cells in the appendix increase the risk of developing colon cancer?

BACKGROUND/AIMS

Epidemiological studies indicate that relevance between appendix and colon cancer is controversial, but unfortunately, there is no data based on examination of immune indicator to reveal the relativity.

METHODOLOGY

This study explored the relation-ship between appendix immunity and the right colon cancer by detecting the presence of NK cells in appendix tissues with immunohistochemistry.

RESULTS

The number of NK cells in the appendix tissue was the highest in patients with appendix inflammation (37.2+1.1), while lowest in patients with colon cancer and normal appendix (30.9+1.7).

CONCLUSIONS

The decrease of NK cells in the appendix tissue is correlated with the increased incidence of right colon cancer.

The "intraendothelial canalicular formation": the route for lymphocyte diapedesis at the level of peripheral and mucosa-associated lymphoid tissue HEVs

How the lymphocyte crosses the blood endothelium during transendothelial migration is demonstrated through the study of serial sections of high endothelial venules (HEVs) of peripheral (mesenteric lymph nodes) and mucosa-associated lymphoid tissue (Peyer's patches, vermiform appendix) during normal lymphocyte homing and experimental intestinal inflammation. The sequence of serial ultrastructural features of lymphocytes englobed in the endothelial wall at different moments of transmigration made it possible to bring out that their transendothelial migration toward the extracellular matrix of lymphoid tissues occurs through an intraendothelial canalicular formation constituted by two adjacent endothelial cells that have closed interendothelial junctions. This intraendothelial canalicular formation, morphologically unlike the transcellular and paracellular migratory pathways, is an innovative model of migratory route for lymphocyte diapedesis that does not compromise the continuity of the endothelial wall. The increased presence of lymphocytes and intraendothelial canalicular formations during experimental inflammation and the metabolic hyperactivity of the spring/summer months compared to the lethargic fast in Chiropters underscores an influence on lymphocyte traffic through the HEVs of the peripheral and mucosa-associated lymphoid tissue.

Microbial induction of B and T cell areas in rabbit appendix

Gut-associated lymphoid tissue (GALT) development requires interaction with the intestinal microbiota. Because murine secondary lymphoid tissue development is driven by positive feedback interactions between B cells and stromal cells, we used in situ hybridization to determine whether intestinal commensals influence such interactions during rabbit appendix development. The features of positive feedback interactions we examined (CXCL13 mRNA expression, B cell accumulation and FDC differentiation) increased during early follicle development, but stalled in the absence of intestinal commensals. These features were reinitiated by commensals that stimulated follicle development and intrafollicular B cell proliferation. Our results suggest that rabbit appendix follicles develop in two phases: an initial phase of B cell recruitment to nascent follicles, possibly through positive feedback interactions, and a subsequent phase of intrafollicular B cell proliferation stimulated by intestinal commensals. In addition, we found that intestinal commensals stimulate appendix CCL21 mRNA expression and T cell area formation.

A murine model of appendicitis and the impact of inflammation on appendiceal lymphocyte constituents

Data indicate that appendicectomy for intra-abdominal inflammation protects against inflammatory bowel disease (IBD). This suggests an important role for the appendix in mucosal immunity. There is no established model of appendicitis. We therefore developed a murine model of appendicitis and examined the effect of inflammation on appendiceal lymphocyte constituents. The caecal patch of specific pathogen-free (SPF)-Balb/c mice was transformed into an obstructed 'appendiceal pouch' by standardized suction and band ligation. Mice were killed and 'pouches' removed for histology and phenotypic analysis of leucocytes by flow cytometry. Serum C-reactive protein (CRP) was determined by enzyme-linked immunosorbent assay. All 'pouches' developed features resembling human appendicitis - mucosal ulceration, transmural inflammation with neutrophils, lymphocytes and occasional eosinophils, and serositis. These changes were most evident between days 7 and 10. There was significant elevation of serum CRP (8.0 +/- 0.3 ng/ml to 40.0 +/- 3.1 ng/ml; P < 0.01), indicating systemic inflammation. Following the initial neutrophil-predominant response, there was an increase in CD4(+) (15.3% +/- 1.2% to 31.0 +/- 2.0%; P < 0.01) and CD8(+) T lymphocytes (3.7% +/- 0.6% to 9.2 +/- 0.8%; P < 0.01). CD25(+) forkhead box P3 (FoxP3)(+) regulatory T lymphocytes were increased by 66% (P < 0.01). Furthermore, significant increases in CD8(+) FoxP3(+) regulatory T lymphocytes were restricted to younger mice (age < 10 weeks, P < 0.003). This is the first description of a murine model of appendicitis. Inflammation resulted in T lymphocyte accumulation associated with an increase in regulatory T lymphocytes, which might explain the age-dependent protective phenomenon. Further exploration will provide insights into the mechanisms of intestinal immune homeostasis and the immunopathogenesis of IBD.

De novo expression of MECA-79 glycoprotein-determinant on developing B lymphocytes in gut-associated lymphoid tissues

Rabbit is one of several species that depend on development of B lymphocytes in gut-associated lymphoid tissues for primary immunoglobulin-repertoire diversification. The rabbit appendix is an important site of early B-lymphocyte development. We previously reported that peripheral lymph node addressin detected by monoclonal antibody (mAb) MECA-79 played a role in recruitment of immature blood-borne B cells into neonatal rabbit appendix. Here, we report expression of an approximately 127 000 MW O-linked sulphated proteoglycan on developing B cells in appendix and Peyer's patches recognized by the mAb MECA-79. Binding of the mAb to B lymphocytes was sensitive to enzyme treatment with O-sialoglycoprotease and expression was partially inhibited by sodium chlorate, a metabolic inhibitor of sulphation. The proportions of MECA-79(+) B lymphocytes gradually increased from < 0.5% at 3 days to > 70% at 6 weeks in appendix and Peyer's patches. The proportions of MECA-79(+) B lymphocytes in spleen and peripheral blood were very low (0.5-2%). However, the MECA-79 determinant was detected on B cells in splenic germinal centres after immunization. In situ labelling of appendix cells showed that the MECA-79 determinant was expressed on fluorescein-labelled B lymphocytes that migrated from appendix into mesenteric lymph nodes. B-cell MECA-79 may be involved in interactions with T cells and/or dendritic cells. Alternatively, because we found that lymphatic endothelium in the thymus-dependent area of appendix, a site for lymphocyte exit, expressed P-selectin (CD62P), interaction of the MECA-79 determinant on B cells with CD62P may have a role in the exit of B lymphocytes from rabbit appendix.

CD27+ B cells in human lymphatic organs: re-evaluating the splenic marginal zone

The marginal zone of human spleens is regarded as an organ-specific region harbouring sessile memory B cells. This opinion has arisen by extrapolating from results obtained in mice and rats. Detection of CD27(+) B cells in situ now revealed similarities among the most superficial region of B-cell follicles in human spleens, reactive lymph nodes, inflamed appendices, tonsils and terminal ilea. The follicular surface in these organs consists of small naïve immunoglobulin D (IgD)(+) CD27(-) B cells predominating in an inner area and larger IgD(+/-) CD27(+) B cells prevailing in a more superficial position. CD27(+) B cells may, however, also occupy the entire follicular periphery around the germinal centre. Together with additional peculiarities this distribution indicates a fundamental microanatomical difference among the human and rodent splenic white pulp. We hypothesize that the follicular periphery represents a recirculation compartment both for naïve and memory/natural reactive B cells in all human secondary lymphatic organs. This assumption implies a difference in recirculation behaviour among human and rodent B memory cells.

CD5+ B cells are preferentially expanded in rabbit appendix: the role of CD5 in B cell development and selection

Although only a small proportion of mouse and human B cells are CD5(+), most adult rabbit B cells express CD5. However, CD5 was not detectable on the majority of B cells in neonatal appendix 1 and 3days after birth. Cell trafficking studies demonstrated that CD5(+) and CD5(-) CD62L(+) B cells from bone marrow migrated into appendix. There, CD5(+) B cells were preferentially expanded and predominated by approximately 2weeks of age. In mutant ali/ali rabbits, VHa2(+) B cells develop through gene conversion-like alteration of rearranged VH genes upstream of deleted VH1a2. Correlated appearance of individual CD5(+) germinal centers and VHa2(+) B-cells in mutant appendix suggests that CD5 binding positively selects cells with a2(+) framework regions that bind CD5. Following negative and positive selection, cells with diversified rearranged heavy- and light-chain sequences exit appendix, migrate to peripheral tissues and constitute the preimmune repertoire of CD5(+) B cells that encounter foreign antigens.

Bacterial-induced inflammation in germ-free rabbit appendix

The intestinal ecosystem is defined by a series of interactions between the microbiota, the mucosal epithelium, and the gut-associated lymphoid tissue (GALT). Perturbations in the fine balance of the interactions between these components can result in gastrointestinal diseases such as inflammatory bowel disease (IBD). The pathophysiology of IBD is thought to develop as a result of dysregulated mucosal immune responses to normal luminal microflora. Several animal models for IBD have been developed and underscore the role of the immune system in development of disease. Most of the existing animal models studying IBD are based on the use of chemically induced IBD or of genetically modified and germ-free animals. It is, however, important to study inflammatory responses that can develop from interactions between bacteria, the mucosal epithelium, and GALT in animals that are not genetically modified or immunocompromised. In this report, we document the use of a germ-free ligated rabbit appendix model to induce inflammatory changes in response to specific bacteria. With the introduction of a Bacteroides vulgatus isolate from humans into the germ-free ligated appendix, we found chronic inflammatory changes, including glandular distortion, gland drop-out, decreased goblet cells, and crypt abscess formation. However, with the introduction of other experimental luminal contents, we observed no inflammation. These results show that specific microbial composition can induce inflammation. We suggest that this model may be useful to study the mechanism by which specific bacteria establish inflammatory responses in the gut.

Regulated expression of peripheral node addressin-positive high endothelial venules controls seeding of B lymphocytes into developing neonatal rabbit appendix

Young rabbit appendix is a homologue of chicken bursa of Fabricius; both are crucial sites for preimmune B-cell repertoire diversification. Here, we report that appendix regulates precursor lymphocyte recruitment for further development by modulating the sites of extravasation. The total area of peripheral node addressin-positive (PNAd(+)) high endothelial venules (HEVs) increased from 1 day to 1 week after birth, remained constant up to 2 weeks and declined to a low and persistent amount by 3 weeks. In normal 1-week and manipulated 5-week appendix where growth of follicles was retarded, PNAd(+) HEVs were present in the basolateral sides of B-cell follicles whereas, in normal 5-wk-appendix these were restricted to T-cell areas. The PNAd was expressed on the lumenal surface of HEVs. The proportions of CD62L(+) B cells in appendix declined from approximately 40% at 3 days to 2-3% at 4 weeks. In lymphocyte transfer experiments, CD62L(+) B cells were preferentially recruited compared with CD62L(-) B cells, anti-PNAd antibody blocked migration of B cells by approximately 50%, and 100 times more B cells were recruited in 1-week compared to 6-week appendix. Thus, a unique spatiotemporal expression pattern of PNAd(+) HEVs is associated with development of B-cell follicles. This regulates migration of blood-borne B-lymphocytes into developing appendix by interacting with CD62L.

Preferential migration of CD62L cells into the appendix in mice with experimental chronic colitis

BACKGROUND

Clinical and experimental studies suggest that appendectomy can protect against development of ulcerative colitis and Crohn's disease. However, how T cells in the appendix affect the development of colitis has not been clarified.

AIM

To investigate the in vivo migration and activation of colitis-inducing CD62L+ cells during development of chronic colitis.

METHODS

CD62L+CD4+ cells were fluorescently labeled and transferred to severe combined immunodeficient (SCID) mice to induce colitis. In vivo migration of T cells into the mucosa of the appendix and colon was quantified by in vivo microscopy after 7 weeks. In a second experiment, unlabeled CD62L+CD4+ cells were transferred, reisolated after 7 weeks, and adhesion molecule (integrin alpha4beta7) and costimulatory molecule (CD154) expression was analyzed.

RESULTS

Six to eight weeks after CD62L+CD4+ cell transfer, SCID mice developed chronic colitis. In vivo microscopic analysis demonstrated a preferential migration of fluorescence-labeled CD62L+CD4+ cells into the mucosa of the appendix versus the colon. Re-isolation of lamina propria cells from mice with colitis confirmed that CD62L+CD4+ cell migration was significantly enhanced in the appendix, compared to the colon (3.5-fold). Furthermore, a higher proportion of CD62L+CD4+ cells re-isolated from the appendix expressed integrin alpha4beta7 and CD154 than from the colon.

CONCLUSION

This study demonstrates the preferential migration of CD62L+CD4+ cells into the appendix as compared to the colon. This migration pattern correlated with upregulation of integrin alpha4beta7 and CD154 (CD40 ligand) on T cells. Our results suggest an important role of the appendix in the pathogenesis of colitis.

Bacterial translocation in the normal human appendix parallels the development of the local immune system

Experimental modes and pathological conditions may result in bacterial translocation (BT), that is, the passage of indigenous bacteria colonizing the intestine through the intestinal mucosa to mesenteric lymph nodes. Yet no data are available on BT in the normal human gut. We determined the occurrence of BT and its extent in histologically normal, incidentally removed human vermiform appendices (VA) from individuals of different ages and correlated the findings with the development with age of associated lymphatic tissue. BT appears to pertain to normal antigen-sampling processes of the GALT in the VA. It also parallels the development of the GALT and its maintenance during adulthood. In the first two weeks after birth, when bacterial colonization of the gut evolves and when the VA lacks the protection of secretory IgA, BT was not detected. Thereafter, BT occurs along with development of the local GALT, which is fully built up after the first year. A physiological uptake of, or invasion by, bacteria may be instrumental (1) for tolerance induction against the indigenous flora and (2) for the stimulation and normal development of the GALT.

Stable expression of the extracellular domains of rabbit recombinant CD5: development and characterization of polyclonal and monoclonal antibodies

Previous studies in our laboratory suggested that there was positive selection of B cells during early development in the appendix of normal and V(H) mutant (ali/ali) rabbits. Preferential expansion and survival of B lymphocytes was affected by the Ig V(H) frameworks 1 and 3 sequences expressed on the cell surface. We demonstrated a specific interaction between rabbit CD5 and the V region of rabbit heavy chains and suggested that CD5 is a potential selecting ligand for B-cell surface immunoglobulin framework region sequences. To further investigate the role of CD5 in rabbit B-cell selection and survival we prepared recombinant constructs and obtained stable expression of the three scavenger receptor cysteine-rich (SRCR) extracellular domains of rabbit CD5. Here we describe the production and purification of this expressed recombinant CD5 protein, polyclonal antibody obtained by immunization of a goat and initial production and characterization of specific mAbs against peptides selected from each sequenced SRCR domain.

Interaction of pathogenic bacteria with rabbit appendix M cells: bacterial motility is a key feature in vivo

Rabbit appendix consists mainly of lymphoid follicles (LF) covered by M cells, the specialized antigen-sampling cells of the mucosal immune system, and surrounded by glandular epithelium. Until now, these M cells have been characterized morphologically and histologically by using cellular markers. Here, the adhesion and transport of pathogenic bacteria were investigated to assess the function of M cells of the appendix. We used the enteroinvasive motile Salmonella typhimurium and the rabbit enteropathogenic non-motile Escherichia coli RDEC-1, which are known to target specifically rabbit M cells of Peyer's patches (PPs). We found that S. typhimurium efficiently attached and was transported through appendix M cells in vivo. In contrast to S. typhimurium, RDEC-1 targeted M cells only ex vivo, when bacteria were allowed to have direct contact with the surface of the follicle. The difference in interaction of the two bacteria with appendix M cells led us to investigate whether this could be correlated with the lack of motility of RDEC-1. We used an aflagellate mutant of S. typhimurium and found that it had the same infection phenotype as RDEC-1. Gene complementation restored the efficiency of infection to that of S. typhimurium wild-type strain. In conclusion, we show that M cells of the appendix display features of the canonical M cells of PP, since they efficiently sample luminal pathogenic bacteria. However, due to the morphology of the appendix, motile bacteria appear to be more potent in their interactions with appendix M cells.

Age-dependent variation in the proportion and number of intestinal lymphocyte subsets, especially natural killer T cells, double-positive CD4+ CD8+ cells and B220+ T cells, in mice

The age-dependent variation in the proportion and number of lymphocyte subsets was examined at various extrathymic sites, including the liver, small intestine, colon and appendix in mice. In comparison with young mice (4 weeks of age), the number of total lymphocytes yielded by all tested organs was greater in adult (9 weeks) and old (40 weeks) mice. The major lymphocyte subset that expanded with age was interleukin-2 receptor (IL-2R) beta+ CD3int cells (50% of them expressed NK1.1) in the liver, whereas it was CD3+ IL-2Rbeta- NK1.1- cells at all intraepithelial sites in the intestine. Although NK1.1+ CD3+ cells were present at intraepithelial sites in the intestine, the proportion of this subset was rather low. The ratio of CD4 to CD8 tended to decrease among natural killer T (NKT) cells and T cells at all intraepithelial sites in the intestine with age. A unique population of double-positive CD4+ CD8+ cells in the small intestine increased in old mice. B220+ T cells were found mainly in the appendix and colon, and the proportion of these T cells decreased in old mice. Conventional NKT cells were very few in Jalpha281-/- and CD1d-/- mice in the liver, while NKT cells which existed in the appendix remained unchanged even in these mice. This was because unconventional CD8+ NKT cells were present in the intestine. The present results suggest that despite the fact that both the liver and intraepithelial sites in the intestine carry many extrathymic T cells, the distribution of lymphocyte subsets and their age-associated variation are site-specific.

The vermiform appendix: not a useless organ

The appendix has often been seen more as a nuisance rather than an important part of the human anatomy. Early misconceptions have led to the indiscriminate removal of the appendix from the body. Long thought to be an evolutionary remnant of little significance to normal physiology, the appendix has more recently been identified as an important component of mammalian mucosal immune function, particularly B-lymphocyte-mediated immune responses and extrathymically derived T-lymphocytes. This structure helps in the proper movement and removal of waste matter in the digestive system, contains lymphatic vessels that regulate pathogens, and lastly, might even produce early defences that prevent deadly diseases. The appendix is one of the guardians of the internal environment of the body from the hostile external environment.

Analysis of mutational lineage trees from sites of primary and secondary Ig gene diversification in rabbits and chickens

Lineage trees of mutated rearranged Ig V region sequences in B lymphocyte clones often serve to qualitatively illustrate claims concerning the dynamics of affinity maturation. In this study, we use a novel method for analyzing lineage tree shapes, using terms from graph theory to quantify the differences between primary and secondary diversification in rabbits and chickens. In these species, Ig gene diversification starts with rearrangement of a single (in chicken) or a few (in rabbit) V(H) genes. Somatic hypermutation and gene conversion contribute to primary diversification in appendix of young rabbits or in bursa of Fabricius of embryonic and young chickens and to secondary diversification during immune responses in germinal centers (GCs). We find that, at least in rabbits, primary diversification appears to occur at a constant rate in the appendix, and the type of Ag-specific selection seen in splenic GCs is absent. This supports the view that a primary repertoire is being generated within the expanding clonally related B cells in appendix of young rabbits and emphasizes the important role that gut-associated lymphoid tissues may play in early development of mammalian immune repertoires. Additionally, the data indicate a higher rate of hypermutation in rabbit and chicken GCs, such that the balance between hypermutation and selection tends more toward mutation and less toward selection in rabbit and chicken compared with murine GCs.

Developing neonatal rabbit appendix, a primary lymphoid organ, is seeded by immature blood-borne B cells: evidence for roles for CD62L/PNAd, CCR7/CCL21, alpha4beta1 and LFA-1

Young rabbit appendix is a homologue of chicken bursa of Fabricius; both are crucial sites for preimmune B-cell repertoire development. We describe here some of the molecules involved in the multi-step recruitment of blood-borne B cells into neonatal rabbit developing appendix. Sialyl-Lewis-x, CD62L and integrins such as LFA-1 and alpha4beta1 were detected on B cells in peripheral blood. Peripheral lymph node addressin (PNAd), a CD62L counter-receptor was observed on appendix HEV. We also detected chemokine receptor CCR7 on peripheral blood B cells and one of the CCR7 ligands, CCL21, on appendix HEV but not in appendix follicles. Higher levels of CXCR5 expression compared to CCR7 on appendix B cells suggest that CXCR5 may be involved in recruitment of B cells into follicles. The proportions of appendix B cells expressing CD62L, sialyl-Lewis-x and alpha4beta1 declined between day 3 and 4 weeks after birth while percentages of Lewis-x+ appendix B cells increased. These changes correlate with the stage of repertoire diversification by gene conversion in both rabbits and chickens. The cross-reactivity of antibodies to mouse or human adhesion molecules described in this study indicates that some of the structures of these important molecules are conserved across species.

Role of commensal bacteria in development of gut-associated lymphoid tissues and preimmune antibody repertoire

Intestinal bacteria are required for development of gut-associated lymphoid tissues (GALT), which mediate a variety of host immune functions, such as mucosal immunity and oral tolerance. In rabbits, the intestinal microflora are also required for developing the preimmune Ab repertoire by promoting somatic diversification of Ig genes in B cells that have migrated to GALT. We studied the mechanism of bacteria-induced GALT development. Bacteria were introduced into rabbits in which the appendix had been rendered germfree by microsurgery (we refer to these rabbits as germfree-appendix rabbits). We then identified specific members of the intestinal flora that promote GALT development. The combination of Bacteroides fragilis and Bacillus subtilis consistently promoted GALT development and led to development of the preimmune Ab repertoire, as shown by an increase in somatic diversification of VDJ-C micro genes in appendix B cells. Neither species alone consistently induced GALT development, nor did Clostridium subterminale, Escherichia coli, or Staphylococcus epidermidis. B. fragilis, which by itself is immunogenic, did not promote GALT development; hence, GALT development in rabbits does not appear to be the result of an Ag-specific immune response. To identify bacterial pathways required for GALT development, we introduced B. fragilis along with stress-response mutants of B. subtilis into germfree-appendix rabbits. We identified two Spo0A-controlled stress responses, sporulation and secretion of the protein YqxM, which are required for GALT development. We conclude that specific members of the commensal, intestinal flora drive GALT development through a specific subset of stress responses.

An “eye” in the gut: the appendix as a sentinel sensory organ of the immune intelligence network

Neural systems are the traditional model of intelligence. Their complex interconnected network of wired neurons acquires, processes, and responds to environmental cues. We propose that the immune system is a parallel system of intelligence in which the gut, including the appendix, plays a prominent role in data acquisition. The immune system is essentially a virtual unwired network of interacting cells that acquires, processes, and responds to environmental data. The data is typically acquired by antigen-presenting cells (APCs) that gather antigenic information from the environment. The APCs chemically digest large antigens and deconstruct them into smaller data packets for sampling by other cells. The gut performs the same function on a larger scale. Morsels of environmental content that enter the gut are sequentially deconstructed by physical and chemical digestion. In addition to providing nutrients, the componentized contents offer environmental data to APCs in mucosa-associated lymphoid tissues (MALT) that relay the sampled information to the immune intelligence network. In this framework, positioning of the appendix immediately after the ileocecal valve is strategic: it is ideally positioned to sample environmental data in its maximally deconstructed state after small bowel digestion. For single-celled organisms, digestion of the environment has been the primary way to sample the surroundings. Prior to the emergence of complex sensory systems such as the eye, even multi-cellular organisms may have relied heavily on digestion to acquire environmental information. While the relative value of immune intelligence has diminished since the emergence of neural intelligence, organisms still use information from both systems in integrated fashion to respond appropriately to ecologic opportunities and challenges. Appendicitis may represent a momentary maladaptation in the evolutionary transition of sensory leadership from the gut to the eye. Relationships between immune dysfunctions and cognition are explored.

Regulation of T-Lymphocyte Trafficking by ICAM-1, MAdCAM-1, and CCR7 in Microcirculation of Appendicular and Intestinal Lymphoid Tissues

OBJECTIVE

Although the appendix is recognized as an inductive site of intestinal inflammation, lymphocyte migration to lymphoid tissues of the appendix has not been characterized. The authors investigated if there are specific features in T-lymphocyte adhesion to microvessels of the appendix compared to mouse Peyer's patches (PPs).

METHODS

T-lymphocyte interaction with postcapillary venules (PCVs) of lymph follicles of the appendix and PPs was observed using an intravital microscope. Antibodies against ICAM-1, MAdCAM-1, or anti-L-selectin were administered prior to lymphocyte administration, and in some experiments CCR7 on T-lymphocytes was desensitized by excess CCL21.

RESULTS

The number of adhered T-lymphocytes reached the maximum value earlier in PCVs of PPs than in those of the appendix. T-lymphocyte adherence was significantly inhibited by anti-MAdCAM-1 at either the appendix or PPs, but adherence in the appendix was also significantly inhibited by anti-ICAM-1, suggesting a dependency on ICAM-1 in the appendix. Histologically, there was a significant ICAM-1 expression in the appendix. Desensitization of CCR7 suppressed T-cell adhesion in PCVs of the appendix and PPs to the same extent.

CONCLUSION

ICAM-1 appeared to be more important in T-lymphocyte sticking in PCVs of the appendix compared with intestinal PPs, while MAdCAM-1 and CCR7 were shown to play important roles in T-lymphocyte adherence in all sites.

Structure, lymphatic vascularization and lymphocyte migration in mucosa-associated lymphoid tissue

In this review, we consider the morphological aspects and topographical arrangement of gut-associated lymphoid tissue (GALT) (solitary and aggregate lymph nodules or Peyer's patches) and of vermiform appendix in the human child and in some mammals. The spatial arrangement of the vessels belonging to apparatus lymphaticus periphericus absorbens (ALPA) and of blood vessels within each lymphoid follicle as well as the ultrastructural characteristics of the lymphatic endothelium with high absorption capacity are considered. Particular attention is also paid to the morphological and biomolecular mechanisms inducing lymphocyte transendothelial migration to the bloodstream by means of lymphatic vessels as well as their passage from blood into lymphoid tissue through the high endothelial venules (HEVs). The preferential transendothelial passage of lymphocytes and polymorphonuclear neutrophils within ALPA vessels of the interfollicular area does not occur following the opening of intercellular contacts, but rather it occurs by means of 'intraendothelial channels'. In HEVs, on the contrary, the hypothesis is plausible that lymphocyte transendothelial migration into lymphoid tissue occurs through a channel-shaped endothelial invagination entirely independent of interendothelial contacts. The lymph of ALPA vessels of the single Peyer's patch is conveyed into precollector lymphatic vessels and into prelymph nodal collectors, totally independent of the ALPA vessels of the gut segments devoid of lymphoid tissue. The quantitative distribution of T lymphocytes in the lymph of mucosal ALPA vessels suggests a prevalent function of fluid uptake, whereas a reservoir and supply function is implicated for the vessels of interfollicular area. The precollector lymphatic vessels and prelymph nodal collectors are considered to be vessels with low absorption capacity, whose main function is lymph conduction and flow.

Histological and immunological features of appendix in patients with ulcerative colitis

Patients with ulcerative colitis (UC) have a less frequent prior history of appendectomy than the general population. The aim of the present investigation was to elucidate histological and immunological characteristics of the appendix in UC and to assess the effect of appendectomy on the disease. Nine subjects with mildly active UC were treated by surgical appendectomy. In four subjects, the histological findings of the appendix were compatible with ulcerative appendicitis. CD3+CD4+CD25+, CD3+CD4+CD45RO+, and CD3+CD8+CD45RO+ appendiceal mononuclear cells were significantly higher in UC than in acute appendicitis and in normal appendix. There was a trend towards higher mRNA transcripts of IFN-gamma in the appendix of UC than those in other two groups. Clinical activity index decreased significantly four weeks after the appendectomy, although the effect was transient. The appendix is a site of involvement in UC, where mononuclear cells are presumed to be at a state of basal activation.

Neutrophil count in the normal appendix and early appendicitis: diagnostic index of real acute inflammation

It is generally accepted that the uninflammed appendix does not contain neutrophils. In view of that, we searched for the presence of neutrophils in 60 uninflammed appendectomies and compared the findings with the neutrophil count in 20 cases of early appendicitis. In the uninflammed appendix, the upper third of the mucosa showed a mean of 0.75 neutrophils (N) per 5 high power fields (HPF), 4.71 N/5 HPF in the middle third, and 2.70 N/5 HPF in the deep third. At the suberosa, a mean of 3.41 and 3.32 N per 10 post-capillary venules in respectively longitudinal and transverse sections of the organ were present. The number of neutrophils in the mucosa showed a positive correlation with the number in the subserosa. In the early appendicitis we observed a mean of 12.53 N/5 HPF in the upper third, 11.33 N/5 HPF in the middle third, and 13.0 N/5 HPF in the deep third; at the subserosa, a mean of 4.95 N/10 post-capillary venules in transverse sections and 4.45 N/10 post-capillary venules in longitudinal sections was observed. No positive correlation between N in the mucosa and subserosa was observed. The count of N in the mucosa of normal appendix and early appendicitis showed a significant difference (P <.005). We conclude that, although present, not more than 10 neutrophils/5 HPF are found in the mucosa of uninflammed appendixes. Neutrophil count in the lamina propria should support the diagnosis of "normal" appendix and could be an indicator for suspecting early appendicitis, preventing underdiagnosis.

[Appendectomy reduces the risk of development of ulcerative colitis]

The etiology and pathogenesis of ulcerative colitis are still unclear. There is, however, a growing consensus that the disease is characterized by a complex interaction between genetic and environmental influences. Many studies in the last few years have suggested that appendectomy reduces the risk of development and improves the course of ulcerative colitis. The underlying mechanism of this effect is unknown. The appendix seems to play a more important role in the development and modulation of the mucosal immune system than believed so far.

Distinct clonal Ig diversification patterns in young appendix compared to antigen-specific splenic clones

The young rabbit appendix is a dynamic site for primary B cell repertoire development. To study diversification patterns during clonal expansion, we collected single appendix B cells from 3- to 9-wk-old rabbits and sequenced rearranged H and L chain genes. Single cells obtained by hydraulic micromanipulation or laser capture microdissection were lysed, PCR amplified, and products directly sequenced. Gene conversion-like changes occurred in rearranged H and L chain sequences by 3-4 wk of age. Somatic mutations were found in the D regions that lack known conversion donors and probably also occurred in the V genes. A few small sets of clonally related appendix B cells were found at 3-5 wk; by 5.5 wk, some larger clones were recovered. The diversification patterns in the clones from appendix were strikingly different from those found previously in splenic germinal centers where an immunizing Ag was driving the expansion and selection process toward high affinity. Clonally related appendix B cells developed different amino acid sequences in each complementarity-determining region (CDR) including CDR3, whereas dominant clones from spleen underwent few changes in CDR3. The variety of combining sites generated by diversification within individual clones suggests that at least some clonal expansion and selection, known to require normal gut flora, may be driven through indirect effects of microbial components rather than solely by their recognition as specific foreign Ags. This diversity of combining sites within B cell clones supports the proposed role of appendix in generating the preimmune repertoire.

Evidence of an Inflammatory Pathologic Condition in “Normal” Appendices Following Emergency Appendectomy

Background.—Appendices removed from patients with suspected appendicitis often appear normal on histologic examination.

Objective.—To study appendix specimens for the expression of inflammatory markers as an indicator of presence of an inflammatory response in this subgroup of patients.

Methods.—Cyclooxygenase 1 and 2, prostaglandin E2, inducible nitric oxide synthase, and major histocompatibility complex class II were investigated by immunofluorohistochemistry using confocal laser microscopy in 15 acutely inflamed appendix specimens, 39 histologically classified “normal” appendices, and 11 negative control specimens.

Results.—Strong expressions of all the inflammatory mediators were found in the mucosa of inflamed appendices, in approximately 50% of histologically normal appendices from patients with a clinical diagnosis of appendicitis, and in none of the normal control specimens.

Conclusion.—This study confirms the existence of a subgroup of appendicitis within the so-called histologically normal appendices in which evidence of an inflammatory pathologic condition is only obvious at a molecular level. The initiating signal for this and all other forms of clinical appendicitis still remains elusive.

Immunocytochemical analysis of cellular infiltrates in human appendicitis

This study was conducted to determine the immunologic cellular composition in human appendicitis and its association with the development of perforated appendicitis. Appendiceal specimens from 27 patients with acute appendicitis were immunostained to detect lymphocyte surface markers. Moreover, the lymphocyte surface markers of peripheral blood were analyzed by laser flow cytometry in 12 patients. Helper T lymphocytes (CD4) were present in all the patients, while B lymphocytes (CD19), natural killer (NK) cells (CD56), and cytotoxic T lymphocytes (CD8) were present in 7 (70%), 10 (100%), and 9 patients (90%) with perforated appendicitis, and in 12 (63.2%), 10 (58.8%), and 6 (54.5%) patients without perforation, respectively. There were significant differences between the patients with a perforated appendix and those without perforation, in the positivity rate for CD8 and CD56 cells (P < 0.05). The number of cells positive for CD56, being NK cells, in the blood from the patients with perforation was significantly lower than that in the blood from those without perforation (P < 0.05). The infiltration of a greater number of cytotoxic T lymphocytes and NK cells was observed in the appendices from patients with perforated appendicitis than in those from patients with nonperforated appendicitis.

Immunohistochemical profiles of 30 monoclonal antibodies against cytokeratins 8, 18 and 19. Second report of the TD5 workshop

In the first report of the TD5 workshop (TD5-1), the epitope specificities of 30 different monoclonal antibodies against cytokeratins 8, 18 and 19 were determined. This second report presents the immunohistochemical profiles of these antibodies using human appendix and normal skin for evaluation. Each antibody was tested by one or two different laboratories recruited from the Dutch Working Group on Immunohistochemistry and Cytochemistry. Eight different laboratories participated. The histological specimens were pretreated by the participants in three different ways for immunohistochemistry: microwave antigen retrieval in citrate buffer, enzymatic digestion to restore epitope exposure, no specific treatment (untreated paraffin-embedded samples), and tested blindly without knowledge of cytokeratin or epitope specificity of the antibodies at three different concentrations of 50, 10 and 1 microg/ml. Most of the tested antibodies (29/30) were useful in at least one pretreatment method, with microwave antigen retrieval being the most sensitive approach. For some antibodies, very high backgrounds were observed. Furthermore, it can be concluded that 11 MAbs performed well using all three staining protocols, including untreated paraffin-embedded sections. Interestingly, all the antibodies with documented selected specificity towards cytokeratin 8 (i.e. 178, 191, 199, 202 and 206) are reactive with an immunodominant region corresponding to amino acids 340-365 on cytokeratin 8, which evidently is well-suited as target for immunohistochemical interactions. Similarly, three antibodies with the same capacity to react with untreated samples had specificity against cytokeratin 19 (i.e. 179, 197 and 204) in the corresponding region in this filament, i.e. amino acids 311-335, or the KS 19.1 epitope. None of the six antibodies against the other major cytokeratin 19 epitope (BM 19.21) were found useful for immunohistochemistry on untreated samples. The overall conclusions from the present investigation are that all cytokeratin-8-specific antibodies with defined epitope specificities were very useful. Only one of the major two epitopes on cytokeratin 19 seems to be available for efficient immunohistochemistry. Cytokeratin 18 exposes some epitopes outside the immunodominant region reactive with the antibodies 190, 203 and 205 which can be used for untreated samples. The implications of these findings are of significance both for diagnostic histopathology and for the biology of tumor marker epitope expression in tissues.

A morphological and immunohistological study of the human and rabbit appendix for comparison with the avian bursa

Diversification of the primary antibody repertoire occurs in young rabbit appendix. As a prelude to molecular investigation of whether human appendix has a similar role, we compared the lymphoid morphology and distribution of common B- and T-cell subsets in frozen and/or paraffin-embedded normal appendix specimens at various ages. IgA, IgM and IgG staining patterns were similar in frozen human and rabbit appendices. The elongated follicles of the young human and rabbit appendices regressed with age to resemble Peyer's patches. Although similar in morphology to the bursa, human and rabbit appendix follicles differ in that they do not involute completely with age and contain significant numbers of germinal center (GC) T cells although the number is low early in life. If the human appendix functions as a primary lymphoid organ, it may occur during the first few months of age when the GC T-cell density is low.

Intestinal microflora and diversification of the rabbit antibody repertoire

The rabbit establishes its primary Ab repertoire by somatically diversifying an initial repertoire that is limited by restricted VH gene segment usage during VDJ gene rearrangement. Somatic diversification occurs in gut-associated lymphoid tissue (GALT), and by about 1-2 mo of age nearly all Ig VDJ genes are somatically diversified. In other species that are known to establish their primary Ab repertoire by somatic diversification, such as chicken, sheep, and cattle, diversification appears to be developmentally regulated: it begins before birth and occurs independent of exogenous factors. Because somatic diversification in rabbit occurs well after birth in GALT, the diversification process may not be developmentally regulated, but may require interaction with exogenous factors derived from the gut. To test this hypothesis, we examined Ab repertoire diversification in rabbits in which the appendix was ligated shortly after birth to prevent microbial colonization and all other organized GALT was surgically removed. We found that by 12 wk of age nearly 90% of the Ig VDJ genes in PBL were undiversified, indicating that intestinal microflora are required for somatically diversifying the Ab repertoire. We also examined repertoire diversification in sterilely derived remote colony rabbits that were hand raised away from contact with conventional rabbits and thereby acquired a different gut microflora. In these remote colony rabbits, GALT was underdeveloped, and 70% of the Ig VDJ genes in PBL were undiversified. We conclude that specific, currently unidentified intestinal microflora are required for Ab repertoire diversification.

Phenotypic pattern of B cells in the appendix: reduced intensity of CD19 expression

The lymphoid tissue of the appendix is considered as part of the gut-associated lymphoid tissue (GALT). In order to understand better the immunological significance of the appendix we analyzed the cellular composition of normal and inflamed human appendix tissue by flow cytometer with special attention to expression of the CD19 and CD5 markers on B cells. Cellular analysis was also performed on peripheral and appendical vein blood samples as well as on omentum and peritoneal fluid samples. The study population included seventeen patients aged 2-15 yr. (mean age - 11.5 yr.) undergoing appendectomy. Ten children were diagnosed with acute appendicitis while 7 had a normal appendix.

RESULTS

Compared to the peripheral blood, the appendix contained a significantly higher percentage of CD19 cells (47.6% of total lymphocytes versus 15%, p<0.0001), and B1 cells (4.98% of total lymphocytes versus 2.42%, p=0.001). In addition, the intensity of CD19-staining was markedly decreased in the appendix (mean - 395.7), and also in the omentum (mean - 398.2) as compared to peripheral lymphocytes (mean - 497.7, p<0.0001 for both comparison). Comparison between the inflamed and the non-inflamed appendices revealed that the inflamed appendix contained a significantly higher proportion of B1 cells (5.64% of total lymphocytes versus 3.53%, p=0.032), and also a higher B1/b cell ratio (0.13 vs. 0.07, p=0.01).

CONCLUSIONS

These results indicate that the appendix tissue contains higher number of B1 (and B) cells compared to the peripheral blood and that these cells play a role in the primary immune response to acute infection/inflammation in the appendix. Appendiceal B cell population is unique in term of CD19 intensity expression on their surface.

Gene-conversion in rabbit B-cell ontogeny and during immune responses in splenic germinal centers

Combinatorial diversity is limited in rabbits because only a few V(H) genes rearrange. Most diversification of the primary repertoire is generated by somatic hypermutation and gene conversion-like changes of rearranged V(H) in B cells that migrate to appendix and other gut associated lymphoid tissues (GALT) of young rabbits. The changes are referred to as gene conversion-like because the non-reciprocal nature of the alterations introduced has not yet been demonstrated. There are many similarities between rabbits and chickens in how their B cells develop and diversify their repertoires. However, although the majority of rabbit B cells may have rearranged and diversified their V genes early in life, some B cells in adult rabbits have rearranged VH sequences that are identical or nearly identical to germline sequences. We found these cells in splenic germinal centers (GC) on days 7 and 10 after immunization of normal adult rabbits with DNP-BGG. By day 15, all rearranged V(H) sequences were diversified. We find an overall pattern of splenic precursor cells whose germline or near germline sequences change both by gene conversion and point mutations during early divisions and mainly by point mutations during later divisions. These events, in parallel with diversification of light chain sequences, may produce the diverse combining sites that serve as substrates for further affinity maturation by selection either within GC or later among emigrant cells in sites such as bone marrow. Some of the sequences altered by gene conversion in splenic germinal centers may also produce new members of the B-cell repertoire in adult rabbits comparable to those produced in GALT of neonatal rabbits.

Neuroimmune appendicitis

BACKGROUND

15-25% of appendices removed from patients with suspected appendicitis appear normal on histological examination. The cause of pain in such patients is unknown. Since the content of neuropeptides seems to be altered in chronic inflammation, we investigated possible changes in peptidergic innervation for substance P (SP), vasoactive intestinal peptide (VIP), and growth-associated protein-43 (GAP-43).

METHODS

Appendices classified as showing acute appendicitis, non-acute appendicitis (clinical signs of acute appendicitis, but histologically not inflamed), or normal were processed for SP, VIP, and GAP-43 immunocytochemistry. The density of SP immunostaining was assessed by digitised morphometry.

FINDINGS

31 appendix specimens were studied (16 acute, 15 non-acute). 16 specimens were used as controls. Expression of GAP-43 was increased in the non-acute appendices. We observed larger amounts of SP-immunoreactive and VIP-immunoreactive nerves in the mucosal layer of the appendix in patients with non-acute appendicitis than in controls and patients with acute appendicitis (mean % area SP-immunoreactive 0.0496 [SD 0.0113] non-acute, 0.0221 [0.0049] acute, 0.0229 [0.0068] controls). In addition, a close spatial relation between SP-immunoreactive and VIP-immunoreactive nerve fibres and lymphoid cells was detected in the outer zone of lymph follicles.

INTERPRETATION

Neuroproliferation in the appendix, in association with an increase in neurotransmitters SP and VIP, may be involved in the pathophysiology of acute right abdominal pain in the absence of an acute inflammation of the appendix. Our data, together with increasing knowledge about the way in which the nervous system and immune cells interact, suggest that neuroimmune appendicitis is a distinct pathological entity.

Enrichment of c-kit+ Lin- haemopoietic progenitor cells that commit themselves to extrathymic T cells in in vitro culture of appendix mononuclear cells

The appendix as well as the small intestine have recently been found to carry c-kit+ stem cells which give rise to extrathymic T cells. In this study, the properties of c-kit+ stem cells in the appendix of mice were further characterized. When appendix mononuclear cells (MNC) were cultured in the presence of stem cell factor, interleukin-3, interleukin-6 and erythropoietin on a methylcellulose culture plate, the population of c-kitdull Lin- and that of c-kithi Lin- cells expanded. Morphological study revealed that these c-kithi Lin- cells were basophilic granular cells (possibly mast cells). Both populations of cultured appendix MNC were then injected into severe combined immunodeficient mice or cultured with Tst-4 thymic stroma cells. These in vivo and in vitro studies demonstrated that c-kitdull Lin- cells were oligopotent haemopoietic progenitor cells which gave rise to extrathymic T cells, while c-kithi Lin- cells lacked haemopoietic progenitor cell activity. In contrast to c-kit+ stem cells in the bone marrow, those in the appendix did not give rise to myeloid cells and conventional thymic T cells under any of the conditions tested. The present results suggest that the appendix primarily comprises c-kit+ cells which give rise to basophilic granular cells and extrathymic T cells and that such c-kit+ cells have the ability to replicate themselves in culture in vitro.

Mucin-related epitopes distinguish M cells and enterocytes in rabbit appendix and Peyer's patches

The biochemical composition of the apical membranes of epithelial M cells overlying the gut-associated lymphoid tissues (GALT) is still largely unknown. We have prepared monoclonal antibodies (MAbs) directed against carbonate-washed plasma membranes from epithelial cells detached with EDTA from rabbit appendix, a tissue particularly rich in GALT. As determined by immunofluorescence microscopy, several MAbs specifically recognized either M cells or enterocyte-like cells of the domes from rabbit appendix, sacculus rotundus, and Peyer's patches. M cells were identified by their large ventral pocket containing lymphoid cells and by specific labeling with antivimentin. Among various characterized MAbs, MAb 104 recognized rabbit immunoglobulins and was used as an apical marker for M cells in the rabbit appendix, MAb 58 selectively stained an integral membrane glycoprotein of greater than 205 kDa located at the apex of M cells, and MAb 214 stained a smaller soluble glycoprotein associated with the apical surfaces from neighboring enterocytes. In addition, both MAbs 58 and 214 also labeled luminal mucus and secretory granules in goblet cells. The selective association of mucin-related molecules at the surfaces of either M cells or enterocyte-like cells of the follicle-associated epithelium suggests that specific carbohydrate antigens are differentially expressed by epithelial cells and could account for the differential binding properties of pathogens.

Extrathymic derivation of gut lymphocytes in parabiotic mice

In adult mice, c-kit+ stem cells have recently been found in their liver, intestine and appendix, where extrathymic T cells are generated. A major population of such thymus-independent subsets among intraepithelial lymphocytes is T-cell receptor (TCR)gamma delta+ CD4- CD8alpha alpha+(beta-) cells, but the origins of other lymphocyte subsets are still controversial. In this study, we examined what type of lymphocyte subsets were produced in situ by such stem cells in the small intestine, large intestine and appendix. To investigate this subject, we used parabiotic B6.Ly5.1 and B5.Ly5. 2 mice which shared the same circulation by day 3. The origin of lymphocytes was identified by anti-Ly5.1 and anti-Ly5.2 monoclonal antibodies in conjunction with immunofluorescence tests. Lymphocytes in Peyer's patches and lamina propria lymphocytes (especially B cells and CD4+ T cells) in the small intestine became a half-and-half mixture of Ly5.1+ and Ly5.2+ cells in each individual of parabiotic pairs of mice by day 14. However, the mixture was low in CD8alpha alpha+, CD8alpha beta+ and gamma delta T cells in the small and large intestines and in CD3+ CD8+ B220+ cells in the appendix. These cells might be of the in situ origin. When one individual of a pair was irradiated before parabiosis, the mixture of partner cells was accelerated. However, a low-mixture group always continued to show a lower mixture pattern than did a high-mixture group. The present results suggest that extrathymic T cells in the digestive tract may arise from their own pre-existing precursor cells and remain longer at the corresponding sites.

Three-dimensional and ultrastructural aspects of the lymphatic vascularization of the vermiform appendix

The aim of the study is to reveal the three-dimensional distribution and ultrastructure of the peripheral absorbing lymphatic vessels of the vermiform appendix, since the gut-associated lymphoid tissue is necessary to the immune responses to the enteric antigens. Corrosion casts showed the beginning of the lymphatic vascularization at the tunica mucosa, which lacks intestinal villi, through a tight, delicate lymphatic network. This network drains the lymph by peculiar straight vessels, distributed in the mucosal beams that separate the adjacent follicle domes, in the fine network of the upper portion of the lymphatic basket, surrounding the lateral walls of the basal and medium portions of each lymphoid follicle. This network, which is made of large caliber vessels that are not dilated like sinuses, continues through small vessels into the large dome-like vessels of the submucosa, which in turn by way of the lymphatic vessels of the muscular tunica, drain into the subserous precollector valved lymphatic vessels that flow into the pre-lymph node collectors. We underlined that the particular fluidity of Neoprene latex and the direct injection method, when compared with other substances and injection methods, provided us with exceptionally clear and precise three-dimensional plastic images of the absorbing lymphatic vessels. Moreover, these images extraordinarily illustrated the preservation of the absorbing lymphatic spatial relationships with blood vessels. Ultrastructural features and three-dimensional models of ultrathin serial sections of the absorbing peripheral lymphatic vessels showed a continuous endothelial wall lacking basal lamina, as well as open junctions between adjacent cells. Moreover, we observed the presence of numerous lymphocytes, together with intense transendothelial migratory activity that occurs through intraendothelial channel formations, dynamic entities, at absorbing lymphatic vessels of the peri-interfollicular lymphoid tissue. Also, we saw that the germinal center, as well as the lymphoid follicle dome, lacked lymphatic absorbing vessels. In addition, many postcapillary high endothelial venules (HEV) were observed with lymphocyte migration into the extravasal compartment. Furthermore, we maintain that the absorbing peripheral lymphatic vessels (ALPA) of the tunica mucosa play an important role in liquid drainage. For the peri-interfollicular vessels, we hypothesize a potential migratory and a reserve capacity for lymphocytes, as well as a conduction activity for the muscular tunica and submucosa vessels.

Appendiceal inflammation in ulcerative colitis

AIMS

Previous uncontrolled reports have suggested that appendiceal inflammation may occur as a discontinuous lesion in ulcerative colitis. This study aims semiquantitatively to compare the prevalence and histological features of appendiceal inflammation in patients with ulcerative colitis and Crohn's disease, using colonic carcinoma and acute appendicitis specimens as controls.

METHODS AND RESULTS

Surgical pathology records and original histological slides for the period 1980-1994 were examined. The prevalence of appendiceal inflammation in ulcerative colitis (24/50, 48%), was higher than in colonic carcinoma (5/65, 8%, P < 0.001), but was similar to that in Crohn's disease (14/27, 52%). Appendiceal inflammation with caecal sparing was seen in nine out of 24 specimens with ulcerative colitis (37%), two out of nine (22%) with Crohn's disease and five out of 65 (8%) with colonic carcinoma. Inflamed appendixes from patients with inflammatory bowel disease showed histological features typical of ulcerative colitis and Crohn's disease rather than acute appendicitis and were significantly less likely to have transmural inflammation. There had been a previous appendicectomy in 3% of ulcerative colitis patients compared with 8% of colonic carcinoma specimens and 21% (P < 0.01) Crohn's disease controls.

CONCLUSION

In ulcerative colitis, as in Crohn's disease, appendiceal inflammation commonly occurs as a skip lesion and histologically resembles the colonic disease rather than acute appendicitis. The low prevalence of appendicectomy supports the hypothesis that the appendix itself may have a central role in the pathogenesis of ulcerative colitis.

High RAD51 mRNA levels in young rabbit appendix. A role in B-cell gene conversion?

The rabbit has a limited number of VH genes that rearrange. As in the chicken, the 3'-most VH1 gene is rearranged in most B lymphocytes. This laboratory reported that by 6 weeks after birth, diversification of rearranged VH genes occurs, at least in part, by gene conversion-like events in the appendix, suggesting that this organ is a homologue of the avian bursa of Fabricius. Rad51 contributes to the repair of double-strand breaks in DNA during somatic and meiotic recombination. The gene was first identified in lower eukaryotes, and later in vertebrates including chicken, as encoding an Escherichia coli RecA-like protein. We report the cloning and sequencing of RAD51 from the rabbit. Because the chicken bursa was shown to express high levels of RAD51 message, we investigated the expression of RAD51 in the rabbit appendix and other tissues. Using a quantitative polymerase chain reaction mimic assay and conventional northern analyses, we found high RAD51 expression in young rabbit appendix comparable to levels in testis where there is an abundance of meiotic recombination. RAD51 levels were three times higher in appendix B lymphocytes compared with T lymphocytes and were lower in adult appendix, as well as in spleen and Peyer's patches of young rabbits. We measured the levels of message in several appendix cell sub-populations obtained by fluorescence-activated cell sorting and found that sub-populations of B lymphocytes corresponding to different stages of B-cell development as well as B cells undergoing isotype switch did not have significantly different mRNA levels.