Lymphoglandular Complexes Research Articles

Lymphoglandular Complex-Like Colorectal Carcinoma-A Series of 20 Colorectal Cases, Including Newly Reported Features of Malignant Behavior.

Distinguishing colon carcinoma that is surrounded by well-circumscribed lymphoid tissue from adenomas involving lymphoglandular complexes can be difficult. We assessed a multi-institutional international cohort of 20 colorectal carcinomas with associated prominent lymphoid infiltrates, which we referred to as lymphoglandular complex-like carcinoma (LGCC). We collected clinical and endoscopic features, including lesion size, endoscopic appearance, location, procedure, follow-up, AJCC stage, and mismatch repair status. We recorded the presence of the following histologic features: haphazard gland distribution, gland angulation, gland fusion, solid nest formation, single-cell formation, stromal desmoplasia, presence of lymphovascular invasion and perineural invasion, presence of lamina propria, cytologic atypia as low- or high-grade, presence of goblet cells in the invasive component, and the presence of a surface lesion. Most cases (9 of 13) were described endoscopically as sessile polyps with an average size of 1.56 cm. Most cases (90%) were associated with a surface lesion, of which the majority were tubular adenomas, though a subset was associated with sessile serrated lesions with dysplasia (3 of 18). All cases of LGCC demonstrated haphazard gland distribution and either gland angulation, fusion, or solid nest formation. A portion of cases demonstrated single-cell infiltration (35%) and desmoplasia (50%), and rarely lymphovascular invasion was present (5%). A subset (10%) of cases invaded beyond the submucosa. Deficient mismatch repair was present in 22% (2 of 9) of cases for which it was performed. In cases of colectomy or completion colectomy, nodal metastasis was present in 38% (3 of 8). No cases demonstrated disease recurrence or disease-specific mortality. Overall, LGCC represents an enigmatic subset of carcinomas that is important to distinguish from adenomas involving lymphoglandular complexes due to its varying prognostic outcomes.

Nodular hyperplasia of lymphoglandular complexes in dogs: A potential diagnostic pitfall for rectal masses.

Lymphoglandular complexes are components of the gut-associated lymphoid tissue that are characterized by submucosal lymphoid aggregates invested by projections of mucosal epithelium. Reports of pathology involving these structures are rare in both human and veterinary literature. Here, the authors report 2 cases of rectal masses excised from dogs following a period of tenesmus and hematochezia. In both animals, the masses were composed of lymphoid tissue closely encompassing tubuloacinar structures. Immunohistochemistry and polymerase chain reaction antigen receptor rearrangement testing demonstrated that the lymphoid population was polyclonal, comprising T and B cells arranged in loosely follicular aggregates centered on the epithelial foci. In light of these findings, a diagnosis of lymphoglandular complex nodular hyperplasia was reported. To the authors' knowledge, this is the first report of this condition in dogs.

Histomorphological, immunohistochemical, and ultrastructural study on ontogeny of ileocaecal lymphoglandular complexes in prenatal and postnatal Indian buffalo: An innate mucosal immune barrier.

The present study was conducted on prenatal and postnatal development of lymphoglandular complexes (LGCs) in ileocaecal region of buffalo fetuses (n=15) ranging from 11.5cm curved crown rump length (CVRL) (80 days) to 100 cm CVRL (299 days) and neonatal buffalo calves (n=10). The fetuses were categorized into three groups based on their CVRL. LGC formation was not evident in ileocaecal junction up to 32 cm CVRL (145 days). At 35 cm CVRL (152 days), diffuse lymphocytes were scattered around the base of glands that encircled them. At 54 cm CVRL (195 days), lymphoid aggregates were present in submucosa around deep submucosal glands and formed primordia of LGCs in ileocaeccal orifice region. At 100 cm CVRL (299 days), these complexes were completely visible grossly. The distinguished lymphoid nodules in submucosa were invaded by submucosal extensions of overlying mucosal glands to form a large clear complex of glands and lymphoid nodules called as "Lymphoglandular complex" at this stage. It is the first report of prenatal development of LGCs in large intestine of buffaloes. Abundant CD3+ T cells were observed towards periphery of LGC. In neonates, these complexes were uniform, few with demarcation into dark and light zones that is, germinal center formation. Lymphocytes interspersed in lamina propria were mainly CD3+ T lymphocytes. In conclusion, the development of LGCs in ileocaecal region started prenatally in terms of all its cellular components into completely developed and immunocompetent to generate mucosal immunity.

Lymphatic Drainage Conduit and Macro Anatomy of Lymphoid System in Large Intestine of Post Weaned Pigs

Background: The gut mucosa is effectively protected by a local organization of lymphoid tissue. In large intestine, isolated lymphoid follicles give rise to solitary lymphoid nodules and lympho glandular complexes, which are responsible for sampling of gut antigen and production of local immunity. Large intestine requires higher level of mucosal protection as because it is the site where food staff remains for a longer period and also for ascending rectal infection. Present study was undertaken highlighting the lymphatic drainage from large intestine and solitary lymphoid nodules of pig. Methods: 1% solution of methylene blue up to 100 micro litters in the one place of submucosa of large intestine as per the standard technique advocated by Smedley et al. (2014) and then stained nearest mesenteric lymph nodes were recorded and re-injected to map the drainage to the next draining lymph node to trace the lymphatic tract. Result: The study was designed on 12 (Twelve) apparently healthy weaned crossbred piglets of 3 to 4 months age irrespective of sex. Gross study revealed the presence of two different types of solitary lymphatic nodules (SLN) viz. scrotiform and faviform. The scrotiform SLN consisted of central small pore was appreciated in colon and rectum, whereas the faviform SLN although present in colon and rectum was devoid of a central pore. The average solitary lymphoid nodules in the large intestine was 427, of which 403 in colon and 24 in rectum and in terminal part of rectum patches of solitary lymphoid nodules of more than 100 numbers were observed. The different lymph nodes involved in the lymphatic drainage of large intestine of pig were colic caecal, anorectal , lumbar aortic, renal , medial lumbar and lateral lumbar lymph nodes. Again, except the right and left lumbar duct, one minor lymphatic trunk was observed parallel to the rectum, draining the lymph from anorecral lymph node to caudal mesenteric lymph node and then to renal lymph node. The celiac trunk and the jejunal trunk joined and formed a common trunk which was again joined by the colic trunk that finally opened into the caudal aspect of cysternachyli.

Histoarchitecture of Large Intestine and Lympho Glandular Complex of Pig

Background: To have a better understanding of the lympho glandular complexes (LGC) along with the histoarchitecture of large intestine and associated M cells, the proposed study have been undertaken. Methods: Present study was conducted on 12 (twelve) numbers of apparently healthy weaned crossbred piglets of 3 to 4 months irrespective of sex. After humane sacrifice of the animals with the approval of institutional animal ethics committee, the representative tissue samples were collected preserved, processed and stained as per standard methods of Luna (1968). Result: Columnar cells predominated the follicle associated epithelium (FAE) and the crypts. M cells were recorded in the follicle associated epithelium as well as in lower crypt epithelium in toluidine blue stained ultra thin sections. M cells were observed with intraepithelial lymphocyte and basally placed euchromatic nucleus. In the colon and rectum of crossbred pigs the lympho glandular complex (LGC) typically consisted of a pore like depression on surface epithelium from which extensions of mucosal glands passed through the circular gap into lamina muscularis mucosae. The lymphatic aggregation of LGC in the lamina propria and tunica submucosa showed three distinct zone viz. follicle, interfollicular area and dome area and distinct FAE could be appreciated. The epithelium lining the solitary lymphatic nodule (SLN) showed (Periodic acid-Schiff) PAS positive reaction. The mucous substance showed strong reaction in the gland in LGC and the FAE epithelium the number of goblet was less. The LGC was formed by aggregation of lymphoid follicles with invagination of crypt gland inside the follicle in the tunica sub mucosa. The follicle associated epithelium devoid of goblet cells were observed on the LGC with interspersed of diffuse migrating lymphocytes in the lamina propria. In the LGC, secondary follicle with interfollicular area was appreciated. In mesenteric lymph node the secondary follicles with inner germinal centre and outer corona could be seen in cortico medullary area. Meshwork of reticular fibers was abundantly present around the crypts in the lamina propria and in the pore like depression of LGC and around the secondary follicle. Collagen fibers could be seen surrounding the LGC and glands. Scanty collagen fibres were observed in the inter-follicular glands. Innervations of nerve fibre was observed around the lymphoid follicle and penetrating the LGC. The mucosal glands were PAS positive.

Pathological characteristics of colorectal adenoma with submucosal pseudoinvasion

Objective: To investigate the pathomorphological characteristics of colorectal adenoma with submucosal pseudoinvasion and to summarize the corresponding pseudoinvasion patterns. Methods: The clinicopathological data of 9 cases of colorectal adenoma were collected at 989 Hospital of PLA Joint Logistics Support Force (4 cases) and Beijing Chaoyang Hospital, Capital Medical University (5 cases), from 2016 to 2019. retrospectively, and the histomorphological characteristics and immunophenotypes were analyzed, and discussed in light of the relevant literature. Results: There were 8 cases of adenoma with stalk. Tumor glands were found in the submucosa at the head end of adenoma, similar to infiltrating adenocarcinoma. The structure and cellular morphology of submucosal glands were very similar to the intramucosal tumor while the local submucosal tumor showed continuity with the intramucosal tumor. The submucosal tumors were lobule-like or nest-like with clear boundary. The outline of the gland was smooth and blunt-round, and there was loose fibromyxoid stroma around the gland, similar to the mucosa propria stroma. Some cases of the submucosal glands were cystic dilated with mucocele formation and hemosiderin deposition. One case with broad stalk-base showed an elevated adenoma with local high grade dysplasia involved in the aggregated lymphoid nodule, forming the lymphoglandular complexes, simulating invasive adenocarcinoma with associated submucosal lymphoid aggregates. Submucosal cancer tissue and intramucosal cancer tissue had continuity, and their morphology was the same. The submucosal tumor was round in the outline, smooth and blunt in the edge, and surrounded by lymphoid tissue. There was no stromal response around the gland to promote the proliferation of connective tissue, neither was there single-cell or small-cell cluster, sharp angle branch of gland, or vascular infiltration. Conclusions: There are two unique morphological patterns in colorectal adenoma with submucosal pseudoinvasion. Morphologically, the data show that one is lobular-like pattern, and the other is lymphoglandular complexes-like pattern. The main features of the two patterns are the same-morphology and continuity of submucosal tumor and intramucosal tumor. The pushed glands were surrounded by the intrinsic membrane stroma and muscularis mucosae in proper order, lacking the typical morphological characteristics of invasive adenocarcinoma.

Prevalence and Pathogenicity of Cryptosporidium suis in Pre‐ and Post‐weaned Pigs

A total of 4338 faecal samples, 135 of sows, 3368 of pre-weaned and 835 of post-weaned piglets from eight farms in South Bohemia, Czech Republic were collected and examined for Cryptosporidium infection. No sow, but 5.7% pre-weaned and 24.1% post-weaned piglets were positive for Cryptosporidium infection. No relationship was found between diarrhoea and Cryptosporidium infection in any of the different age groups (pre- and post-weaned piglets). Four piglets, which were sporadically shedding cryptosporidia in faeces, were necropsied. Neither clinical signs of diarrhoea nor macroscopical changes were found. Histologically, a moderate infection of cryptosporidia was detected in the glandular epithelium along the large intestine, with predisposition to the ansa centralis of the colon. No inflammatory response in the lamina propria was observed. Cryptosporidia were also commonly found in the glandular epithelium of submucosal lymphoglandular complexes in the colon. Cryptosporidium isolates from all farms were identified as Cryptosporidium suis using molecular markers (SSU rRNA). All of the C. suis strains obtained were larger [6.2 (6.0-6.8) x 5.5 (5.3-5.7) microm] than any isolate described so far [4.6 (4.4-4.9) x 4.2 (4.0-4.3) microm] and did not appear to be infective for neonatal BALB/c mice.

The pathology of diverticulosis coli.

Left-sided diverticulosis coli is a common condition in western communities, with 30% to 50% of adults over the age of 60 being affected. It predominantly involves the sigmoid colon. The diverticula (pseudodiverticula) are pockets of mucosa bounded by muscularis mucosae and invested with a thin layer of submucosa, that are forced out through weak points in the muscularis propria, the tips ending in the colonic subserosa. The weak points in the muscle coat are the sites of entry of the nutrient vessels of the colonic mucosa. Diverticulosis is attributed to increased colonic intraluminal pressure while straining at stool in individuals who eat low-fiber diets. Muscular hypertrophy, shortening of the bowel, and thickened mucosal folds due to mucosal redundancy are characteristic of this condition. Complications of diverticulosis include bleeding, diverticulitis, peridiverticular abscess, perforation, stricture, and fistula formation. However, most individuals with diverticulosis are asymptomatic, without evidence of complications. Mucosal changes in the diverticula in uncomplicated diverticulosis include an increased lymphoid infiltrate, development of lymphoglandular complexes, mucin depletion, mild cryptitis, architectural distortion, Paneth cell metaplasia, and ulceration. The mucosa of the remainder of the sigmoid colon (ie, the nondiverticular mucosa) is usually normal, but in about 1% of cases it has features that are indistinguishable from ulcerative colitis or from Crohn's disease (segmental colitis associated with diverticular disease, SCAD). Such cases pose a difficult diagnostic challenge as patients with SCAD respond to medical or surgical therapy for diverticular disease, whereas those with ulcerative colitis or Crohn's disease will develop other manifestations of their disease in time and require different treatment. In SCAD, the mucosal changes are confined to the area of diverticulosis; therefore, histologic evaluation of the rectum (which is unaffected by diverticulosis) and more proximal bowel can be helpful in the differential diagnosis.

ENHANCEMENT OF DISEASE AND PATHOLOGY BY SYNERGY OF TRICHURIS SUIS AND CAMPYLOBACTER JEJUNI IN THE COLON OF IMMUNOLOGICALLY NAIVE SWINE

Campylobacter jejuni, a leading cause of bacterial gastroenteritis, has different age distribution and disease expression in developing and developed countries, which may be due to the endemnicity of infection and the age of acquisition of immunity. Differences in disease expression are not solely dependent on the C jejuni strain or virulence attributes. Another modulating factor in developing countries may be endemic nematode infections such as Trichuris, which drive type 2 cytokine responses and down-regulate type 1 immune responses. In this study, three-day-old germ-free pigs given dual infections with Trichuris suis and C jejuni had more frequent, more severe diarrhea and severe pathology than pigs given no pathogens, only T. suis, or only C jejuni. These pigs had significant hemorrhage and inflammatory cell infiltrates in the proximal colon where adult worms were found, and abscessed lymphoglandular complexes in the distal colon with intracellular C jejuni. Pigs given only C jejuni had mild clinical signs and pathology, and bacteria in feces or extracellular sites. Pigs given T. suis or no pathogens had no disease and minimal pathology. Thus, these agents synergized to produce significant disease and pathology, which was site specific.

ENHANCEMENT OF DISEASE AND PATHOLOGY BY SYNERGY OF TRICHURIS SUIS AND CAMPYLOBACTER JEJUNI IN THE COLON OF IMMUNOLOGICALLY NAIVE SWINE

Campylobacterjejuni, a leading cause of bacterial gastroenteritis, has different age distribution and disease expression in developing and developed countries, which may be due to the endemnicity of infection and the age of acquisition of immunity. Differences in disease expression are not solely dependent on the C. jejuni strain or virulence attributes. Another modulating factor in developing countries may be endemic nematode infections such as Trichuris, which drive type 2 cytokine responses and down-regulate type 1 immune responses. In this study, three-day-old germ-free pigs given dual infections with Trichuris suis and C. jejuni had more frequent, more severe diarrhea and severe pathology than pigs given no pathogens, only T. suis, or only C. jejuni. These pigs had significant hemorrhage and inflammatory cell infiltrates in the proximal colon where adult worms were found, and abscessed lymphoglandular complexes in the distal colon with intracellular C. jejuni. Pigs given only C. jejuni had mild clinical signs and pathology, and bacteria in feces or extracellular sites. Pigs given T. suis or no pathogens had no disease and minimal pathology. Thus, these agents synergized to produce significant disease and pathology, which was site specific.

The pathogenesis of necrotic proliferative colitis in swine is linked to whipworm induced suppression of mucosal immunity to resident bacteria

Mucohemorrhagic enteritis syndrome in swine has a complex etiology with largely unknown pathogenesis. We have observed that inoculation of pigs with swine whipworm, Trichuris suis, initiates an interaction with resident bacterial flora to induce mucohemorrhagic enteritis. The role of bacteria in this mixed infection was demonstrated using 4 treatment groups. One group of pigs was inoculated with 2500 embryonated T. suis eggs alone, while a second group received T. suis eggs along with broad spectrum antibiotic treatment. Two other control groups of pigs were uninoculated and were either treated with antibiotic or untreated. Pigs inoculated with T. suis eggs exhibited diarrhea, mucosal edema, inflammatory cell infiltration, bacterial accumulation at the site of worm attachment in the proximal colon, and intestinal adenomatosis associated with the intracellular Ileal symbiont intracellularis bacteria. In addition, enlarged lymphoglandular complexes (LGCs) containing numerous extracellular bacteria, eosinophils, lymphocytes, macrophages, and neutrophils were observed in the distal colon. The other group of pigs that was inoculated with T. suis but treated with antibiotics had lesions localized to the site of worm attachment and histologically normal LGCs with no invasive bacteria in the distal colon. The groups of uninoculated pigs, with or without antibiotic treatment, exhibited no pathology or bacterial invasion. It appears that the complex pathogenesis of necrotic proliferative colitis in pigs may be linked to worm induced suppression of mucosal immunity to resident bacteria. Further, the association between bacteria, lymphocytes and macrophages in the LGCs of pigs infected with T. suis suggests an antigen-processing role for these structures in the colon. Further, the complex pathogenesis of necrotic proliferative colitis in pigs may be linked to worm induced suppression of mucosal immunity to resident bacteria.

Lymph pathways associated with three types of follicle structure found in gut-associated lymphoid tissue of horse ileum.

In the horse ileum, lacteals in the villi are continuous with prelymphatic intercellular channels and a plexus of lymphatic sinuses in the lamina propria that encircle the domes of the follicle/dome structures and proprial follicles. These sinuses may act as the major entry site for many of the lymphocytes migrating from gut-associated lymphoid tissue via the lymphatic system. Vessels from this plexus penetrate the muscularis mucosae and lymph flows into lymphatic vessels within the interfollicular tissue between the follicles of both follicle/dome structures and lymphoglandular complexes (LGCs). No lymphatic vessels leave the follicles, but intercellular pathways of the follicles are continuous with those in the surrounding interfollicular tissue and follicular sinuses around the base of the follicles. These pathways appear to provide the only available lymphatic route for lymphocytes leaving LGCs to enter the lymphatic system. Lymph from the interfollicular tissue enters deep submucosal lymphatic vessels, containing prominent valves, which drain into other vessels transporting lymph from the surface of the ileum.

Lymphoid tissues of the ileum in young horses: distribution, structure, and epithelium.

Lymphoid tissues in the ileum of young horses form raised plaques that are macroscopically visible from the mucosal surface. These are termed "ileal lymphoid patches". These patches are variable in size, shape and position within the ileal wall, occasionally lying along the site of mesenteric attachment. Within lymphoid patches, follicles exist in three different morphological forms: follicle/dome structures, proprial follicles, and lymphoglandular complexes (LGCs). In follicle/dome structures, the majority of the follicle lies in the submucosa and merges with a dome in the lamina propria through a gap in the muscularis mucosae. In proprial follicles, the majority, or all, of the follicle is found in the lamina propria, and in LGCs, the follicles lie in the submucosa and communicate with the intestinal lumen via a central invagination of epithelium that extends vertically through a gap in the muscularis mucosae. Follicle-associated epithelium covers the follicle/dome structures and proprial follicles. It consists of enterocytes, cells morphologically resembling M cells, intraepithelial lymphocytes, goblet cells, and amine-precursor uptake and decarboxylation (APUD) cells. The epithelium of LGCs is mainly populated by immature enterocytes, intraepithelial lymphocytes and goblet cells. Cells with coarse, long microvilli are also present. Information regarding the presence of LGCs in the small intestine is scant, but LGCs have been well described in the large intestine of many species. Further investigation will be required to determine if factors exist that are common to both the ileum of the horse and the large intestine of other species to influence the development of LGCs at these specific sites.

Ultrastructural study of the uptake of ferritin by M cells in the follicle-associated epithelium in the small and large intestines of pigs

SUMMARY Uptake of ferritin by M cells in follicle-associated epithelium at various sites in the small and large intestines was examined in 4 healthy 5-week-old pigs by use of electron microscopy. A 2.5% solution of ferritin in saline was injected into ligated loops of the jejunum and ileum containing aggregations of lymphoid follicles (Peyer's patches), as well as into intestinal loops containing lymphoglandular complexes at the ileocecal junction, in the central colonic flexure, and in the rectum. As negative control, saline solution was injected into loops at identical localizations. After an exposure period of 2 hours, uptake of ferritin by M cells, but not by enteroabsorptive cells of the small and large intestines, was observed. Numbers of M cells with ferritin and total M cells were counted and the percentage was calculated. Total number of M cells was highest in lymphoglandular complexes in the rectum and lowest on domes of the ileal Peyer's patch. High numbers of M cells with ferritin were found on domes of the jejunal Peyer's patch, and in lymphoglandular complexes at the ileocecal entrance and in the rectum. Only a few M cells on domes of the ileal Peyer's patch and in lymphoglandular complexes in the central colonic flexure contained ferritin. The percentage of M cells with internalized ferritin was similar on domes of the ileal Peyer's patch, and in lymphoglandular complexes at the ileocecal junction and in the rectum. It was higher on domes of the jejunal Peyer s patches and lower in lymphoglandular complexes of the central colonic flexure. Ferritin was found in the apical tubulovesicular system, multivesicular bodies, and a few vacuoles in the central area of M cells. Ferritin was exocytosed into the lateral intercellular spaces next to M cells. Uptake of ferritin by intraepithelial cells in the follicle-associated epithelium could not be documented, but ferritin was present in vesicles of subepithelial macrophages.

Uptake of ferritin by follicle-associated epithelium in the colon of calves.

Uptake of macromolecules (e.g., ferritin) by M cells in follicle-associated epithelium in small and large intestine was investigated in three healthy, conventionally raised, 2- to 3-week-old, female Holstein Frisian calves. A 2.5% solution of ferritin was injected into the ligated loops in mid-jejunum, in terminal ileum, in the ascending colon adjacent to the ileocecal junction, and in the proximal loop of the ascending colon containing gut-associated lymphoid tissue. After exposure times that ranged from 82 to 165 minutes, ferritin was detected in M cells of domes in the small intestine, as well as in cells in follicle-associated epithelium of proprial lymphoid nodules and lymphoglandular complexes of colon that morphologically resembled M cells of small intestine. Ferritin was found in apical invaginations, apical vesicles, multivesicular bodies, basal vesicles, and adjacent intercellular spaces. In addition to ferritin, apical vesicles, multivesicular bodies, and intercellular spaces contained 50-nm membrane-bound particles. More ferritin was endocytosed by M cells of the small intestine than by M cells of the large intestine. In the large intestine, higher amounts of ferritin were found in M cells of follicle-associated epithelium overlying proprial lymphoid nodules than in M cells of follicle-associated epithelium in the depth of lymphoglandular complexes. Based on these results, we concluded that M cells of follicle-associated epithelium in the colon of calves provide a route for antigen uptake into the intestinal lymphoid system.

Hyperplasia of lymphoglandular complexes in colon segments in Hirschsprung's disease: a form of diversion colitis.

This is a study of the size and number of lymphoglandular complexes (LGDs) in the resected segment of aganglionic left colon of 20 children (mean age 26 months) obtained several months to years after being defunctionalized by proximal colostomy, compared with 5 controls (mean age 20 months). All the resected aganglionic segments had a nodular mucosa. The number of LGCs/mm of muscularis mucosae was 0.58 +/- 0.2; in controls the number was 0.24 +/- 0.12 (P less than .0025). The mean size of LGCs in aganglionic colon was 1.23 +/- 0.27 mm, and in controls it was 0.57 +/- 0.21 (P less than .0005). Because LGCs have been related to antigen processing, hyperplasia of LGCs in defunctionalized colonic segments of Hirschsprung's disease may represent a reaction to stagnant contents. Its combination with cryptitis (present in six cases) may represent a form of diversion colitis, a condition recognized in adults in bypassed colonic segments after surgical diversion of the fecal stream.

M cells in the rectum of calves

The morphology of gut-associated lymphoid tissue and the ultrastructure of overlying lymphoepithelium of newborn and three-week-old conventionally raised calves were compared. In all calves patches of lymphoid nodules were found in the terminal rectum. In newborn calves lymphoid nodules in the submucosa with caps of lymphoid tissue in the lamina propria predominated. In three-week-old calves lymphoglandular complexes were as numerous as lymphoid nodules with caps. Scanning and transmission electron microscopical examination of superficial lymphoepithelium over caps and lymphoepithelium in epithelial diverticula of lymphoglandular complexes revealed groups or single cells morphologically resembling M cells, but with widely varying apical processes. To investigate whether these putative M cells in rectal lymphoepithelium internalise and transport macromolecules across the epithelial barrier, ferritin was injected into the rectum of three-week-old calves. Eighty to 150 minutes after exposure ferritin was detected in cells resembling M cells. Thus these cells ought to be considered as M cells. It may be hypothesised that gut-associated lymphoid tissue with specialised lymphoepithelium in the rectum of calves provides a route for the uptake of antigen.

Porcine colonic lymphoglandular complex: distribution, structure, and epithelium.

Lymphoepithelium and cells specialized for uptake and transport of foreign matter are characteristic of antigen sampling organs, including lymphoglandular complexes (LGCs). Distribution, histologic structure, and epithelial ultrastructure of colonic lymphoglandular complexes were determined in 5- to 13-week-old pigs. LGCs averaged 1,231 in number per colon, displayed a characteristic distribution pattern, and were most evenly distributed in colons of older pigs. LGCs consisted of well-defined submucosal masses composed of lymphatic nodules and internodular lymphoid tissue penetrated by radially branching extensions of mucosal glands. Epithelial diverticula of each LGC entered the submucosa as a group through a circular collar derived from the muscularis mucosae. LGC epithelium contained goblet cells, cuboidal and columnar enterocytes, enteroendocrine cells, individual and clustered intraepithelial leukocytes, and cells morphologically compatible with follicle-associated epithelial cells/M cells. We regard the colonic LGC as a distinct mucosal lymphoid organ and suggest a significant role for it in local and systemic immune responses. The porcine colonic LGC may serve as a model for the human LGC.

Gut-associated lymphoid tissue in the large intestine of calves. II. Electron microscopy.

Scanning electron microscopy of lymphoid tissue in the large intestine of three germfree calves (age 3, 6, and 7 days) revealed two different units: propria nodules and lymphoglandular complexes (LGC). Propria nodules had lymphoid tissue predominantly in lamina propria and were covered by distinct follicle-associated epithelium which lacked goblet cells; nodules were surrounded by wide crypts, which were also lined by follicle-associated epithelium towards the luminal side. Lymphoglandular complexes had lymphoid follicles in the tunica submucosa; epithelial diverticulae extended through the muscularis mucosae branching into the lymphoid nodule. In centers of lymphoglandular complexes, protrusions of lymphoid tissue were covered with distinct follicle-associated epithelium. By transmission electron microscopy cells compatible with M cells in the small intestine of calves and cells with characteristics of both enteroabsorptive and M cells were found. Follicle-associated epithelium of propria nodules and lymphoglandular complexes differed only in the relative frequency of cell types.

Gut-associated lymphoid tissue in the large intestine of calves. I. Distribution and histology.

Gut-associated lymphoid tissue (GALT) in the large intestine was characterized in 12 calves (10 to 84 days old) obtained at necropsy (7, group A) or healthy animals (5, group B). Patches of mucosal lymphoid follicles were in all calves at ileocecal entrances (ICE), 23-42 cm distal to the ICE in the proximal loop of the ascending colon (proximal colon [PC] patch), and in the terminal rectum. PC patches varied from 8 to 30 cm in length. Solitary lymphoid follicles were found in the cecum of three calves, between the ileocecal entrances and the PC patch in four calves, adjacent to the PC patch in all calves, and in the ampulla recti. GALT occupied 7.8% of the large intestinal wall in animals of group A: 0.6% at the ileocecal entrance, 4.8% in the proximal colon, and 2.4% in the rectum. There were two different types of mucosal lymphoid follicles in group B: propria nodules with lymphoid follicles predominantly in the lamina propria, and lymphoglandular complexes with lymphoid follicles in the submucosa. In three 3-, 6-, and 7-day-old, germfree calves, distinct follicle-associated epithelium covered propria nodules and covering folds in depths of the lymphoglandular complexes; it was characterized by numerous intraepithelial cells and lack of goblet cells.