Early kinetics of Toxoplasma gondii infection in mice infected orally with cysts of an avirulent strain

We determined the early kinetics of Toxoplasma gondii infection in Swiss Webster mice inoculated with the avirulent C strain by counting parasites in the blood, spleen, Peyer's patches, liver, lungs, and brain. Animals were orally inoculated with cysts on day zero (D0), and parasites were counted using a tissue culture method at 12, 24, and 36 hr and 2, 3, 7, 10, 14, 21, 30, 50, and 72 days postinfection. The spleen and Peyer's patches were the first organs found parasitized, on D2 and D3, respectively, followed by the lungs and liver on D7 and the brain on D10. No parasitemia was detected. This suggests that early dissemination of this avirulent strain from the intestine into the general circulation occurs essentially via the lymphatic system. Parasites persisted at a high level in the brain during the chronic phase. In the lungs, parasites were no longer detected by D72, while parasite numbers initially declined in the spleen and Peyer's patches but then showed a second peak, possibly due to recirculation of T. gondii. These results suggest that lymphoid organs play a key role in T. gondii dissemination during the acute phase and may also constitute a persistent source of parasite resurgence.

Isolation and experimental oral transmission in pigs of a porcine reproductive and respiratory syndrome virus isolate

A virus inducing a cytopathic effect on porcine alveolar macrophages was isolated from the lungs of a pig with respiratory problems and lesions of proliferative and necrotizing pneumonia. The isolate was found to react with porcine reproductive and respiratory syndrome virus (PRRSV) monoclonal antibodies by indirect immunofluorescence and was designated LHVA-93-3. The virus could also be propagated on the MARC-145 cell line. The LHVA-93-3 macrophage-passaged isolate was inoculated orally or intranasally in four-week-old specific pathogen-free pigs. Histologically, focal to multifocal lesions of proliferative, necrotizing and interstitial pneumonia could be observed in the lungs of pigs inoculated orally or intranasally, 6 and 10 days post-inoculation. Virus could be reisolated from essentially the same tissues including serum following both routes of infection. The distribution of PRRSV antigens in fixed tissues as determined by immunogold silver staining (IGSS) was similar in orally or intranasally inoculated pigs. The results of this experimental transmission study indicate that pigs may become infected by PRRSV following oral as well as intranasal exposure.

Malaria-induced increase of splenic gamma delta T cells in humans, monkeys, and mice

The number and distribution of gamma delta T cells in spleens from patients who died of cerebral malaria and from rhesus monkeys severely infected with Plasmodium coatneyi were examined by immunocytochemistry. gamma delta T cells were significantly increased in these spleens. In a rodent malaria model using Plasmodium chabaudi adami, an avirulent strain of murine malaria parasites, the degree of parasitemia appears to be modulated by the number of gamma delta T cells in the spleen. As parasitemia increases, these T cells increase in number. At some critical point, gamma delta T cells in collaboration with macrophages and alpha beta T cells apparently start to clear parasitized erythrocytes from the blood, leading to an abatement of the parasitemia, which is followed by a reduction in the number of gamma delta T cells. This gamma delta T cell phenomenon may be responsible for the self-limiting infection in mice.

[Radiobiological aspects of increased radioresistance of murine epithelial stem cells from patches of Peyer]

The fraction of the survived intestinal crypts associated with patches of Peyer is higher to those non-patch-associated crypts of mice for three inbred strains. The difference in the survival between associated and non-patch-associated crypts increases with dose of gamma-irradiation. This difference for old mice is less than for young mice. Pre-irradiation (5 Gy) of mice one week before the conditioned gamma-irradiation cannot modify the difference in the survival between associated and non-patch-associated crypts. Radioprotection of mice by hypoxic gas mixture (10% O2) cannot modify this difference. Pre-treatment of mice by dextran-sulfate alone or in combination with hypoxic gas mixture decreased the survival of intestinal crypts associated with patches of Peyer to the level of non-path-associated crypts. The difference in the survival between two subpopulation of intestinal stem cells is less after neutron irradiation than after gamma-irradiation.

Salmonella typhimurium initiates murine infection by penetrating and destroying the specialized epithelial M cells of the Peyer's patches

Salmonella species are known to initiate infection of mammalian hosts by penetrating the intestinal epithelium of the small bowel. These bacteria preferentially interact with Peyer's patches which are collections of lymphoid follicles making up the gut-associated lymphoid tissue. We infected murine ligated intestinal loops with invasive and noninvasive Salmonella typhimurium strains for 30, 60, 120, and 180 min and examined the infected tissue by transmission electron microscopy. Within 30 min, we found that invasive S. typhimurium exclusively entered M cells found within the follicle-associated epithelium (FAE) of the Peyer's patches. Initially, interactions between invasive bacteria and enterocytes adjacent to the M cells were not found. Invasion of M cells was associated with the ability of the bacteria to invade tissue culture cells. S. typhimurium mutants, which were noninvasive for tissue culture cells, could not be found in ligated loops associated with M cells or enterocytes after incubations of 30, 60, 120, or 180 min. At 60 min, internalized invasive S. typhimurium were cytotoxic for the M cells. Destruction of an M cell formed a gap in the FAE which allowed organisms to invade enterocytes adjacent to the dead cell. Later in the infection process (120 and 180 min), the presence of bacteria beneath the FAE correlated with changes in the cytoarchitecture of the lymphoid follicle. In addition, replicating Salmonella began to enter both the apical and basolateral surfaces of enterocytes adjacent to infected M cells.

Lymphocyte subpopulations in jejunal and ileal Peyer's patches of calves with experimental Salmonella dublin infection

Changes of lymphocyte subpopulations in jejunal and ileal Peyer's patches (JPP and IPP) of six calves inoculated with Salmonella dublin were investigated at 9 hours, 1, 2, 3 and 7 days post inoculation (p.i.) using immunohistochemistry. Reactive areas and area percentages of B-lymphocytes, as well as CD4+, CD8+ and gamma delta T-lymphocytes within the different compartments of PP were estimated using computer-assisted morphometric analysis. A significant, linear decline of the areas of lymphoid follicles and domes in JPP and IPP due to depletion of B-lymphocytes was found. The rate of decline was similar in JPP and IPP, but more severe in lymphoid follicles than in domes. Intraepithelial cells in follicle-associated epithelium changed from predominantly B-lymphocytes in controls to CD8+ T-lymphocytes in inoculated calves and clusters of B-lymphocytes were observed above domes at days 1 and 2 p.i. Areas of CD4+ and CD8+ T-lymphocytes within lymphoid follicles and domes were increased at 3 and 7 days. p.i. resulting in decreased compartmentalization of the normally segregated T- and B-lymphocyte populations. The increase of CD4+ and CD8+ T-lymphocytes was, however, significant in lymphoid follicles in the JPP only. No significant changes in the amount and distribution of gamma delta T-lymphocytes were observed.

[The dynamic cellular composition of Peyer's patches in mice with an experimental Trichinella spiralis infection]

The morphological study of Peyer's patches of mice during experimental T spiralis infection has revealed a dual-frequency of the response of small intestinal lymphoid tissue to the helminth. Activation of Peyer's patches was seen early in the intestinal and muscular phases of invasion.

Development of the early mucosal lesions in experimental inflammatory bowel disease--implications for pathogenesis

The purpose of this study was to better establish the morphologic basis of the early mucosal lesions of experimental inflammatory bowel disease because understanding the development of these lesions has important pathogenetic implications. Sprague-Dawley rats were given 1.5% hydrolyzed lambda-carrageenan orally for 30 days. This produced small intestinal lesions which were then evaluated. Light microscopy showed an increased amount of inflammatory cells in the gut wall with prominent Peyer's patches, microgranulomas, crypt abscesses, pin-point ulcerations, and a repair reaction. Scanning electron microscopy revealed pin-point ulcerations in relation to Peyer's patches. Transmission electron microscopy, in addition to the above findings, showed disruptions of enterocyte microvilli and terminal webs. Follicle-associated epithelium appeared to be a predictive site for the development of crypt abscesses and pin-point ulcerations. Enzyme-linked immunoadsorbent assays indicated that orally administered carrageenan elicited a systemic antibody response. Our results suggest that damage to enterocyte microvilli and terminal webs may be important early events in the morphogenesis of the lesions.

Enumeration of selected leukocytes in the small intestine of BALB/c mice infected with Cryptosporidium parvum

Neonatal, suckling BALB/c mice inoculated with Cryptosporidium parvum produce an infection characterized by continuous shedding of oocysts that spontaneously clears by the time the animals are three weeks of age. Neonatal mice were used to characterize the leukocyte subgroups present in Peyer's patches from the ileum and jejunum of Cryptosporidium-infected and healthy mice. After infection, ileal Peyer's patches showed a predominant CD8+ response, with abundant monocytes-macrophages (MOMA-2+) and nonlymphoid dendritic cells (NLDC-145+ cells). In contrast, jejunal Peyer's patches showed more T lymphocytes than ileal patches, with a predominance of CD4+ cells and many dendritic NLDC-145+ cells and MOMA-2+ cells. The present results showed that ileal and jejunal Peyer's patches are functionally different in response to Cryptosporidium parasites. These findings suggest a preferential involvement of jejunal Peyer's patches in T cell-dependent immunity against the parasite, whereas ileal patches may be associated with B cell expansion and maturation.

Experimental infection of vaccinated and non-vaccinated lambs with Mycobacterium paratuberculosis

A study of the pathogenesis of paratuberculosis and the effects of vaccination was carried out on 17 Rasa lambs, allocated to four groups. Vaccination seemed to accelerate the progress of the infection, and led quickly to healing. The only site of early lesions was the interfollicular areas in the Peyer's patches. This would suggest an explanation both for the location of paratuberculous lesions in the ileum in clinical cases, and for the lower susceptibility to infection of adult animals, in which the intestinal organized lymphoid tissue is greatly diminished. Thus, a critical role of the Peyer's patch in the establishment of M. paratuberculosis infection is suspected.

Immunoglobulin and T-cell receptor gene rearrangements in lesions of mucosa-associated lymphoid tissue

Twenty-one cases of mucosa-associated lymphoid tissue (MALT) lesions have been analyzed by Southern blot for immunoglobulin heavy chain (IgH) and T-cell receptor beta chain (TcR beta) gene rearrangements (GR). The sites included colon, stomach, liver, nasopharynx, salivary and lacrimal gland, conjunctiva, tonsil, breast, and lung. Two of the lesions (parotid and conjunctiva) were malignant lymphomas and one case showed lymphoproliferative disorder. In the cases of malignant lymphomas, IgH GR were detected, and in the case of lymphoproliferative disorder, both IgH and TcR beta genes were rearranged. Among the remaining 18 cases, 9 showed inflammatory infiltrate, 3 lymphoid hyperplasia, 3 atypical lymphoid hyperplasia, 1 carcinoma of the tonsil, 1 breast carcinoma, and one was a sample of normal Peyer's patches. Among these 18 cases, 3 showed TcR beta GR, 6 showed double IgH and TcR beta GR, and 4 IgH GR. Often multiple rearranged bands were observed, composing 10-30% of the total DNA analyzed. The control tissue (Peyer's patches) showed no GR. Because IgH and TcR beta GR are used to determine monoclonal proliferations of T and B lymphocytes, which occur in malignant lymphomas, it is vital to determine the specificity of such a test. This report stresses the fact that in MALT lesions false-positive results are not uncommon and therefore the results of IgH and TcR beta GR studies have to be interpreted with caution. The presence of multiple GR in the inflammatory lesions indicates proliferation of minor monoclonal populations that can be detected with the use of Southern blot technology.

[Case reports of hemorrhagic diathesis in calves with bovine diarrhea virus infection]

Clinical and pathological findings in six veal calves suffering from haemorrhagic diathesis are reported. Further pathological and virological results were highly suggestive of mucosal disease (BVD). No virus isolation or classification was possible. The post mortem results indicated that the virus might have been cytopathogenic. The cases are discussed and compared with similar field and experimental publications dealing with thrombocytopenia in veal calves in the USA. These are the first reports of cases published in Germany.

The growth of mouse hybridoma cells between Peyer's patch lymphocyte and myeloma cell in the gastrointestinal tract. A model for human multiple lymphomatous polyposis of the gastrointestinal tract

To elucidate the mechanism of multiple lesions in human primary lymphoma or multiple lymphomatous polyposis of the gastrointestinal tract, we developed a experimental model utilizing mouse hybridoma cells. Syngeneic mice were immunized with human hemoglobin via gastric intubation and a hybridoma clone (13c) between the Peyer's patch cell and mouse myeloma cell was obtained. The 13c cells were infused into normal syngeneic mice through a lateral tail vein. About 2 months after injection mice were sacrificed and their viscera were scrutinized histologically. All 11 mice receiving 13c showed multiple tumors at the colon, microscopic massive invasions at the small intestine, and scattered invasions at Peyer's patch, mesenteric lymph nodes and the spleen, exhibiting the similar distribution patterns as in human multiple lymphomatous polyposis of the gastrointestinal tract. ME-1 or MU-1 cells (hybridomas between P3 and mouse spleen cell) were distributed at the liver, spleen and paraaortic lymph nodes. Such migration patterns of 13c cells and their adherence to vessel walls suggest that multiple invasions may be lymphocyte homing receptor-mediated phenomena.

Pathogenesis and early lesions in extranodal lymphoma

Extranodal lymphomas that arise in tissues normally devoid of lymphoid tissue provide a unique opportunity for the study of the pathogenesis of lymphoma without the distraction of surrounding lymphoid tissue. This applies particularly to mucosa-associated lymphoid tissue (MALT) B-cell lymphomas, so named because they recapitulate the structure of normal MALT rather than that of lymph nodes. Before these lymphomas develop, MALT accumulates, usually in response to autoimmune injury associated with chronic gastritis caused by Helicobacter pylori, Sjõgren's syndrome, Hashimoto's thyroiditis or other as yet uncharacterized disorders. The factors that induce MALT in these tissues and the point at which a clonal population of B cells arises are currently under investigation. Other extranodal lymphomas that arise in a setting of long prodromata include enteropathy associated T-cell lymphoma (EATL) which occurs in some patients with coeliac disease and lymphomas associated with immunodeficiency that appear to be caused, at least in part, by the Epstein-Barr virus. Application of new, particularly molecular genetic, techniques to the study of these extranodal lymphomas should also provide insight into the aetiopathogenesis of the more common nodal lymphomas.

M cells are damaged and increased in number in inflamed human ileal mucosa

Ileocolonoscopy and biopsies of patients with spondylarthropathy revealed gut inflammation in 62% of the cases. In order to better understand the pathogenetic mechanisms of spondylarthropathy related gut inflammation the follicle associated epithelium was examined. Biopsies from 9 controls and 18 patients with spondylarthropathy were studied by electron microscopy. Membranous (M) cells were investigated in normal and inflamed ileum. In normal mucosa M cells were scarce whereas in inflamed mucosa their number was increased (up to 24% of follicle associated epithelial cells). They showed a thin rim of cytoplasm covering groups of lymphocytes. In chronic ileitis necrotic M cells, ruptures of M cell cytoplasm and lymphocytes entering the gut lumen were observed. The bursts of M cells at the top of the lymphoid follicles lead to interruption of the gut epithelial lining and give luminal content access to the lymphoid tissue. This pathogenetic mechanism may cause aphthoid ulcers.

A microbiological, histopathological and immunohistological study of the intragastric inoculation of Listeria monocytogenes in mice

The course of murine infection after intragastric inoculation of L. monocytogenes was investigated by immunocytochemical, histopathological and microbiological techniques. L. monocytogenes antigen was observed in epithelial cells of intestinal mucosa overlying Peyer's patches, but not in mucosa devoid of them. This suggests that penetration of L. monocytogenes into the host organism may take place through epithelium overlying Peyer's patches. The efficiency of bacterial penetration appeared to be low, as shown by the small amounts of L. monocytogenes antigen detected and the low counts of bacteria in organs. Gross or histopathological lesions in the intestinal tract were not observed. The presence of L. monocytogenes in spleen, liver and in maxillary and mesenteric lymph nodes, confirmed that the systemic course of infection by this route of inoculation is similar to that of the parenteral routes. The results emphasize the subclinical character of murine listeriosis by the oral route.

Cell-mediated immune injury in the intestine

Epithelial adaptation clearly occurs during the course of intestinal cell-mediated immune responses to alloantigens. The adaptive response is similar to that seen in a number of enteropathies, namely villus atrophy, crypt hypertrophy, and crypt cell hyperplasia. In human fetal gut, polyclonal activation of lamina propria CD4+ T cells produces the same epithelial adaptive responses. Although these data provide overwhelming evidence that cell-mediated immune responses can cause enteropathy, the demonstration of antigen-specific T cells in the lamina propria of patients with enteropathy is still lacking, even in a disease as well-characterized as celiac disease. Epithelial adaptation in experimental and clinical situations, however, must involve a change in the mechanisms and mediators involved in normal intestinal homeostasis, such as epidermal growth factor and transforming growth factor-alpha and -beta, and in the interactions between epithelial cells and the underlying stromal cells.

Modulatory effects of metanil yellow on immunity in rodents

Pathomorphological and immunological studies were carried out on rodents following oral administration of 0, 0.1, 0.25 and 0.5% (w/w) metanil yellow, mixed in diet, for 30 days. No significant change in hematologic parameters and histologic architecture of liver, kidney, mesenteric lymph node, thymus and urinary bladder was observed except for mild desquamation of intestinal villi and moderate changes in Peyer's patches of small intestine with higher doses. Among immunological parameters, significant enhancement in the primary humoral immune response (anti-SRBC IgM plaque forming cells of spleen) was observed with the lowest dose of metanil yellow while higher doses produced opposing effects. An elevated cutaneous delayed type hypersensitivity (DTH) reaction to SRBC was seen in 0.1% metanil yellow treated animals but higher doses did not influence the reaction. The treatment also caused changes in functional capabilities of macrophages. Although these immune alterations could hardly influence the local immunity of gut, as measured by the capacity of animals to cause rejection of Nippostrongylus brasiliensis parasite, the potential to modulate the immunity in general by metanil yellow however assumes considerable biological significance.

[The morphological changes in the organs of the lymphoid system in the experimental infection of mice with Trichinella spiralis]

The dynamics of morphological changes in central and peripheral organs of the lymphoid system of mice experimentally invaded with Trichinella spiralis was studied. The immune response of the host was shown to have two phases including two peaks and the suppression period. The activation of the lymphoid organs was observed in earlier intestinal and muscular phases, and the suppression was noted in migration phase of invasion.

Histopathologic and immunohistochemical changes in gut-associated lymphoid tissues after treatment of rabbits with dexamethasone

Corticosteroids cause impaired cell-mediated immunity which may encourage development of gastrointestinal and respiratory infections. In order to better understand the effects of corticosteroids on gastrointestinal immunity, immunological and histological changes in gut-associated lymphoid tissues were examined after intravenous administration of dexamethasone to rabbits. In treated animals, lymphoid domes and follicles were considerably reduced in size, and the dome epithelial layer was markedly depleted of M cells and lymphocytes. There were numerous open lesions at the luminal surface of dome epithelium, consistent with necrosis of M cells, and a striking depletion of follicular B cells in treated animals. These immunologic and histologic effects of corticosteroids could have found profound, deleterious effects on mucosal immune responses and host resistance to microbial infections.

Experimental reproduction of porcine proliferative enteritis

A campylobacter-like bacterium, isolated from the terminal ileum of a pig with porcine proliferative enteritis (PPE), was used to initiate PPE in healthy crossbred pigs. Post-mortem examinations of pigs infected orally with the bacterium revealed thickening of the terminal ileum, haemorrhage within the ileum, degeneration of ileal villi and large quantities of bile and mucous in the ileal contents. Histopathological examination revealed that the terminal ileum, ileo-caecal valve and caecum from infected pigs had partial or total loss of mucous membrane, hyperplasia of the crypt and glandular epithelial cells, campylobacter-like organisms in and around the Peyers' patches and lymphoid aggregates in the mucosa. The causative organism was re-isolated from the intestinal specimens of infected animals post-mortem. In control animals, kept under the same conditions, no evidence of abnormality was observed in the terminal ileum, ileo-caecal valve or caecum.

Protein malnutrition alone and in combination with endotoxin impairs systemic and gut-associated immunity

Because protein-malnourished or endotoxemic patients are at an increased risk of developing nosocomial infections, this study was performed to investigate the effects of protein malnutrition and endotoxemia, alone and in combination, on systemic and intestinal immunity. Protein malnutrition was created by feeding the animals a solid diet containing 0.03% protein. Subgroups of these protein-malnourished mice were killed after being challenged with saline or endotoxin on days 0, 7, 14, or 21. At death, the animals were weighed, tissues were harvested for histologic analysis (ileum, mesenteric lymph node [MLN], liver, and spleen), mitogen responsiveness (MLN, Peyer's patches, and spleen), and xanthine oxidase measurements (ileum and cecum). Separate groups were evaluated for survival. Both the saline and endotoxin-challenged mice had lost about 30% of their body weight after 21 days on the low-protein diet. The protein-malnourished mice were more susceptible to endotoxin-induced mortality (70% at 21 days) than the normally nourished mice (0%) (p less than .001). The mitogen responsiveness of the protein-malnourished mice to the T-cell mitogens (PHA and Con-A) progressively decreased the longer the mice were protein malnourished, and this decreased in blastogenic responsiveness was associated with histologic evidence of lymphoid atrophy. In contrast, the blastogenic response to the primarily B-cell mitogen, PWM, was largely preserved. The endotoxin challenge further depressed the immune state of mice tested after 0, 7, or 14 (but not 21) days of protein malnutrition. Thus, both protein malnutrition and endotoxin impaired systemic and gut-associated immune responsiveness to mitogens. However, in the protein-malnourished mice, the degree of immune suppression did not correlate with endotoxin-induced mortality.

Morphological alteration of gut-associated lymphoid tissue after long-term total parenteral nutrition in rats

The morphological alteration of gut-associated lymphoid tissue (GALT) induced by long-term absence of dietary stimulation was investigated. Male Wistar rats weighing approximately 230 g were maintained with total parenteral nutrition (TPN). Control rats were allowed to have the same amount of the solution orally. After two weeks, the morphological alteration of GALT was examined. Although no significant difference in weight gain was noted between the two groups, the area comprised by Peyer's patches was decreased in TPN rats. The number of transported lymphocytes and the ratio of helper T (Th) cells to suppressor/cytotoxic T (Ts/c) cells in intestinal lymph were lowered after TPN treatment. In an immunohistochemical study of the rat ileum, the number of T cells and the Th/Ts/c ratio were decreased both in the intraepithelial spaces and in the lamina propria of TPN rats. The percentage of interleukin-2 receptor-positive cells and the number of IgA-containing cells in the lamina propria were significantly reduced in TPN rats. These results suggest that dietary stimulation might play a role in the maintenance of GALT function and morphology.

Pathogenesis of Venezuelan equine encephalitis virus infection in mice and hamsters

The pathogenesis of Venezuelan equine encephalitis (VEE) virus infection was compared in intraperitoneally inoculated mice (n = 24, 6 to 8 weeks old) and hamsters (n = 9, 90-110 g) using histopathology and immunohistochemical localization of VEE virus antigen. Infected mice developed paralysis, and the majority died by 9 days after inoculation. In contrast, hamsters did not survive beyond 3 days after inoculation, and they did not develop any neurologic signs. VEE virus antigen, demonstrated by immunoperoxidase staining, and pathologic changes were present in extraneural organs of both mice and hamsters. There was more severe involvement in hamsters, particularly in Peyer's patches of the distal small intestine. There was a severe encephalomyelitis in mice, but pathologic changes were not well established in the brains of hamsters before death. VEE virus antigen was widespread in the central nervous system of both mice and hamsters. VEE virus was found to be highly neurotropic in hamsters and had a similar distribution in the brain as in mice, but hamsters died from their extraneural disease before major central nervous system disease developed.

Pathogenesis of lymphoid lesions in murine experimental listeriosis

Adult female Swiss albino mice were infected intraperitoneally or subcutaneously with Listeria monocytogenes Serovar 4b or 1/2a and killed at intervals. Thymus, spleen, Peyer's patches and a variety of lymph nodes, including the jejunal (mesenteric), mediastinal, lumbar, mandibular and superficial inguinal, were examined by histopathology and by immunocytochemistry for detection of L. monocytogenes antigen. Similar results were obtained with both Serovars and by both routes of inoculation used. In the spleen, L. monocytogenes was detected, by immunoperoxidase staining, as soon as 4 h after inoculation, inside phagocytic cells located predominantly in the marginal zone of the white pulp. This was followed by inflammation, necrosis and depletion of lymphoid cells, which extended in extreme cases to the whole organ. Inflammatory lesions diminished progressively at 5 to 6 days after inoculation. In animals dying of the infection, a severe necrotizing splenitis was present. Depletion of lymphoid cells and inflammatory changes were widespread in the lymph nodes and to a lesser extent in the Peyer's patches. An extensive necrotizing lymphadenitis was the prominent lesion in severely affected nodes. Inflammatory lesions and detection of L. monocytogenes antigen started around the venules of high endothelium. A thymus depletion, not associated with the multiplication of bacteria in the organ, was also a constant feature of the infection. This study suggests that L. monocytogenes (1) is transported to the spleen and to the lymph nodes by phagocytes, entering the organs by the marginal sinus in the spleen and by the venules of high endothelium in the lymph nodes; (2) multiplies in these cells as well as in neutrophilic granulocytes (the latter rapidly migrate to the affected zones); and (3) induce a splenitis and lymphadenitis, involving predominantly T cell-dependent areas, with a necrotizing component in severe cases. From our observations it is concluded that infection of the lymphoid system is a major feature in the pathogenesis of murine listeriosis.

Effect of surgical and chemical in ovo bursectomy on lymphocyte density scores and histological evaluations of primary and secondary lymphoid organs in hypertensive and hypotensive turkeys

The effects of surgical and chemical in ovo bursectomy on the histology of primary and secondary lymphoid organs were studied in hypertensive and hypotensive lines of turkeys. The effects of bursectomy were measured by determining the presence of lymphatic nodules and the presence of lymphocytes in secondary lymphoid organs: spleen, cecal tonsil, Meckel's diverticulum, and Peyer's patches; as well as in the thymus and bursa of Fabricius. No treatment effect on splenic nodule formation occurred, but a significantly lower lymphocyte density score was present in the surgically bursectomized group. Both nodule formation and lymphocyte density scores for the cecal tonsil and Peyer's patches were significantly reduced in the surgically bursectomized and testosterone-treated groups as compared with the control and sham groups. The most consistent depression in lymphatic scores in both the surgically and chemically bursectomized groups occurred in the Peyer's patches followed by cecal tonsils and Meckel's diverticulum. As expected, there were no differences in thymocyte density scores. There was no consistent effect on lymphatic scores due to blood pressure selection; however, the hypertensive line showed significantly lower scores than the hypotensive line in the bursa, cecal tonsils, and Peyer's patches. No differences between the sexes were noted in any organ.

Acute disseminated Aspergillosis in a cow with special reference to penetration and spread

Acute disseminated aspergillosis caused by Aspergillus fumigatus is reported in a 4-year-old cow given broad spectrum antibiotics and anti-inflammatory therapy. All stomach compartments were infected and hyphal invasion of gastric blood vessels was the probable source of generalization to the liver, lung and kidneys. Throughout the Peyer's patches of the jejunum there were acute necrotic foci with Aspergillus hyphae and similar foci occurred in the corresponding mesenteric lymph nodes. This points to the Peyer's patches being a portal of entry for A. fumigatus to the lymphatic system of the intestine.

B95a, a marmoset lymphoblastoid cell line, as a sensitive host for rinderpest virus

We reported earlier that B95a, an Epstein-Barr virus-transformed marmoset B lymphoblastoid cell line, is more susceptible to infection with measles virus than other cells. The cell line also was found to be susceptible to infection with the lapinized Nakamura III (L) strain of rinderpest virus and various strains derived from it. The B95a cell line was therefore the only host cell system available for the propagation and quantification of the L strain. In contrast to the adaptation of the L strain to Vero cells which results in a diminution of virulence in rabbits, the propagation of the virus in B95a cells preserved the virulence and some other properties in rabbits. Furthermore, when Vero cell-adapted variants of the L strain with diminished virulence were serially passaged in B95a cells, virulence in rabbits was gradually regained.

Rejection of multivisceral allografts in rats: a sequential analysis with comparison to isolated orthotopic small-bowel and liver grafts

Multivisceral isografts and allografts were transplanted to Lewis rats, and the histopathologic changes were studied in the liver, intestine, and other constituent organs. Rats receiving isografts had indefinite survival with maintenance of weight. With multivisceral allografts (from Brown-Norway donors), the intestinal component was rejected more severely than the companion liver and with about the same severity as when intestinal transplantation was performed alone. Intestinal rejection in either circumstance was a lethal event, causing death in 10 to 12 days. The earliest (by day 4) and most intense cellular rejection was in the Peyer's patches and mesenteric lymph nodes. This was associated with or followed by cryptitis, epithelial cell necrosis, focal abscess formation, mural necrosis, and eventual perforation. Liver allografts transplanted alone or as part of multivisceral grafts also had histopathologic evidence of rejection, but this was self-limiting and spontaneously reversible when the liver was transplanted alone. Thus the Achille's heel of multivisceral grafts is the intestinal component that is not protected by the presence of the liver in the organ complex. Better immunosuppression should permit successful experimental and clinical transplantation of such grafts.

T-2 toxin impairment of murine response to Salmonella typhimurium: a histopathologic assessment

T-2 toxin and other trichothecene mycotoxins experimentally impair normal immune function and may predispose humans and animals to infectious disease. In this study, the histopathologic effects of Salmonella typhimurium challenge concurrently with sublethal T-2 toxin exposure were examined in the Salmonella-resistant C3H/HeN mouse. Oral administration of T-2 toxin (1 mg/kg) every other day for 10 d had little effect on the tissues examined when compared to control animals. Mice challenged with S. typhimurium and then treated with T-2 toxin every other day for 10 d had markedly larger and more bacterial-related lesions in the spleens, kidneys, and livers than animals challenged with S. typhimurium alone. Differences in bone marrow, Peyer's patches and ileal tissues were less discernable between S. typhimurium and S. typhimurium plus T-2 toxin treated groups. These results were consistent with previous findings that T-2 toxin compromised murine resistance to S. typhimurium infection and ultimately caused death in animals challenged with a sublethal dose of the organism.

Peyer's patches in experimental Salmonella dublin infection in calves. Microvascular and epithelial changes contributing to atrophy of lymphoid follicles

Six calves were infected per os with Salmonella dublin and killed nine hours to seven days later. Early changes included occlusion of capillaries with a hyaline material, particularly in the ileal Peyer's patch (PP). Central areas of the follicles contained hemorrhages and edema. In later stages the follicle-associated epithelium (FAE) of both the jejunal and ileal PP was fused with the adjacent epithelium and the follicles were collapsed. As judged from 5'nucleotidase histochemistry, follicles were depleted of lymphocytes whereas reticular cells were retained. Carbonic anhydrase (CA) histochemistry showed a decreased reaction in the ileal FAE and a reduced amount of CA reactive material in the follicles of the ileal PP, indicating loss of FAE differentiation and function. Hyaline material and fibrinous thrombi were seen occluding the blood capillaries and the lymphatics, respectively. The villi were atrophied and covered with thick fibrin deposits. Using antifibrinogen antibodies, immunoperoxidase stained fibrin in the lymphatics and the lumenal deposits but not the hyaline material in the capillaries. Reaction for CA indicated that this hyaline material originated from erythrocytes. Factors contributing to the follicle atrophy may include anoxia due to stasis in the microcirculation with the formation of erythrocyte thrombi, and reduced lymphopoiesis due to a decrease in the stimulating factors provided by the FAE.

Pigment resembling atmospheric dust in Peyer's patches

Terminal ileal pigmentation was observed during colonoscopy, in surgically resected specimens, and autopsy cases. Microscopically, black pigment was seen within macrophages in the lamina propria and submucosa, closely related to the Peyer's patches. Three ilia from autopsies with no macroscopic pigmentation showed deposits following digestion and X-ray microanalysis. X-ray microanalysis of tissue sections and digestates revealed a heterogenous population of particles. Approximately one third of the particles contained calcium and phosphorus and were considered endogenous. The rest of the particles were predominantly aluminum and magnesium-rich silicates, which were considered exogenous. Analysis of particulate extracted from lungs and ilea of four autopsy cases demonstrated remarkable similarities in composition. These findings suggest that the ileal deposits are derived from atmospheric dust. This pigment is believed to migrate into the Peyer's patches through the M cells of the follicle associated epithelium, although other mechanisms for pigment deposition cannot be ruled out.

Anti-mu treatment suppresses immunoglobulin light-chain gene expression and Peyer's patch development

Anti-mu treated mice have been used extensively as a model for suppressed B-cell development [Murgita R. A., Mattioli C. A. and Tomasi T. B., Jr. (1973) J. exp. Med. 138, 209; Manning D. D. (1975) J. Reticuloendothel. Soc. 18, 63; Manning D. D. and Jutila J. W. (1972) J. Immun. 108, 282; Janeway C. A., Jr., Murgita R. A., Weinbaum F. I., Asofsky R. and Wigzell H. (1977) Proc. natn. Acad. Sci. U.S.A. 74, 4582; Hayglass K. T., Naides S. J., Benacerraf B. and Sy M.-S. (1985) J. Molec. Cell. Immun. 2, 107; Manning D. D. (1972) J. Immun. 109, 1152; Cooper M. D., Kearney J. F., Gathings W. E. and Lawton A. R. (1980) Immun. Rev. 52, 29; Burrows P. D., Kearney J. F., Lawton A. R. and Cooper M. D. (1978) J. Immun. 120, 1526]. However, little molecular evaluation has been performed on these animals to determine the level at which B-lineage cells are arrested. Experiments reported here were designed to determine the effects of anti-mu treatment of newborn mice on Ig-specific mRNA expression in lymphocyte populations. Newborn CBA/J mice received i.p. injections of goat anti-mu IgG or non-immune goat IgG, every 2 days, from birth until age 4 weeks. The degree of B-cell suppression in anti-mu treated mice was evident by low serum Ig levels and lack of surface Ig+ cells in splenic lymphocytes. Morphologically, spleens of B-cell depleted mice were slightly reduced or normal size, while the total area of Peyer's patches (PP) was three-fold less than control mice. Spleen cells from anti-mu suppressed mice contained high levels of mu-mRNA, but markedly reduced levels of mRNA specific for other Ig heavy-chain isotypes, as determined by DNA excess dot blot and Northern blot hybridizations. RNA specific for other sequences (actin or IL-2 receptor) was not affected and hybridization to parent plasmid (pACYC) was not detected. In addition, suppression of kappa- and lambda-mRNA accumulation was evident. This was surprising, since the target for anti-mu treatment appears to be a B-cell population expressing intact surface IgM, a stage in B-cell development in which both mu- and light-chain-specific mRNA accumulation should be detected. Our results suggest one of the following models: (1) anti-mu treatment deletes all Ig+ cells from the animal, so that only mu expressing pre-B-cells remain; or (2) anti-mu suppresses B-cell development by inhibiting kappa and lambda transcription, perhaps by some feedback mechanism in which the presence of surface Ig is required to maintain light-chain transcription.

M cells and granular mononuclear cells in Peyer's patch domes of mice depleted of their lymphocytes by total lymphoid irradiation

The cytoarchitecture of Peyer's patches that were depleted of their lymphocytes by total lymphoid irradiation (TLI) was examined with particular attention to the effects on M cells in the follicle epithelium and on mononuclear cells in follicle domes underlying the epithelium. Five-month-old, specific pathogen-free Balb/c mice were irradiated with 200-250 rad/day, five times a week to a total dose of 3400-4250, and their Peyer's patches were either fixed for electron microscopy or frozen for immunohistochemistry 1-4 days after completion of irradiation. Control mice were examined at the same time intervals. Follicle domes of TLI mice had approximately one fourth the epithelial surface area of domes of control mice. Within the epithelium, lymphoid cells were virtually depleted after TLI, and yet the epithelium contained M cells. In control mice, most M cells were accompanied by lymphoid cells in invaginations of the apical-lateral cell membrane. In TLI mice, most M cells did not have such apical-lateral invaginations and were columnar shaped. Other than lacking lymphocytes, these cells appeared to be mature M cells. Some M cells did have lymphoid cells or granular mononuclear cells below their basal membranes, adjacent to the basal lamina. Below the epithelium, the proportion of granular mononuclear cells was greatly increased following TLI. The retention of M cells and the increase in proportion of granular mononuclear cells in follicle domes are consistent with selective depletion of lymphocytes following TLI. Persistence of M cells without lymphocytic invaginations after TLI suggests that M cells can differentiate in the absence of, or at least in the presence of very few, lymphocytes, and that invagination by lymphocytes is not necessary to maintain mature M cell morphology.

Role of M cells in initial antigen uptake and in ulcer formation in the rabbit intestinal loop model of shigellosis

Strains of Shigella flexneri with different invasive and pathogenic potentials were inoculated into the intestinal lumen of acutely ligated loops in nonimmune rabbits. After 90 min, tissues processed for ultrastructural as well as light microscopy showed that the bacilli were phagocytosed by M cells over lymphoid follicles of Peyer's patches and carried in vacuoles into the epithelium. Nonpathogenic as well as pathogenic strains were readily taken up regardless of the presence of the 140-megadalton virulence plasmid. More virulent than avirulent shigellae were found in M cells at 90 min, reflecting replication or preferential uptake of the virulent strains. Heat-killed shigellae of the virulent strain were taken up by M cells to the same degree as the avirulent strains. Incubation of the bacteria for 18 h resulted in surface ulceration which was limited to epithelium overlying lymphoid follicles (M cell areas) in acute loops exposed to the virulent shigellae. Villus epithelium adjacent to the ulcerated follicular domes was intact, although there was mucus depletion. In the present study, we found that pathogenic shigellae appear to replicate in the M cells, escape from the phagocytic vesicles, and thereby initiate the ulcerations in this experimental model of dysentery. While initial antigen processing in the gut for a mucosal immune response may require uptake of luminal microorganisms by M cells, this may pose a threat under some circumstances.

Immune-related alterations in aged gut-associated lymphoid tissues in mice

To study whether senescence-induced changes in the gut-associated lymphoid tissue (GALT) are mainly quantitative, several parameters were examined in three age groups of BALB/c mice (1-2, 12-14, and 24-28 months old). A substantial senescence-associated decline in the number of lymphoid cells was found in the mesenteric lymph nodes (MLN) and spleen (SPN), and especially in the Peyer's patches (PP), but not in the lamina propria (LP). The distribution of lymphocyte subsets in these tissues was also altered with an absolute reduction of T cells--in particular, a L3T4+ helper/inducer T-cell marker-bearing subset. These changes were most remarkable in PP, followed by MLN. The in vitro proliferative reactivity and the production of each isotype-specific immunoglobulin (Ig) by PP, MLN, and SPN were profoundly affected when T-cell-dependent (Td) B-cell mitogens were used, but minimally affected when T-cell-independent (Ti) B-cell mitogens were used. The isotype-specific Ig content of small-intestinal perfusates was also influenced by aging, but only to a minor extent, as exemplified by a decrease in IgA levels in the fasting condition. Thus, despite the defects in the quantity and distribution of lymphocytes in aged PP and MLN, the finding of little change in the total amount of secreted IgA in aged intestine suggests that gut IgA-mediated luminal immune responses could remain nearly unaltered with senescence. The constancy of intraluminal IgA levels could be of physiological significance in host defense at the gut mucosal surface in aged mice.

Intussusception revisited: clinicopathologic analysis of 261 cases, with emphasis on pathogenesis

In the ten-year period from 1978 through 1987, 261 patients with intussusception were admitted to Chang Gung Memorial Hospital. The diagnosis was established by barium enema or at laparotomy. The patients were divided into two groups; there were 228 children ranging in age from 1 month to 14 years, and 33 adults. Among the children, 134 (59%) were male and 94 (41%) were female, a ratio of 1.4:1. There was no clear seasonal incidence. The age group most commonly affected was between 3 and 11 months of age (72.4%). The classic triad of abdominal pain, vomiting, and rectal bleeding was encountered in 187 cases (82%). Two hundred one cases (88%) were idiopathic, without any definite leading point. In these cases, the ileocecal area was the site most commonly involved (82%), hypertrophic Peyer's patches of the terminal ileum being responsible for 39% of the idiopathic intussusceptions in the ileocolic area. Enlargement of the mesenteric lymph nodes occurred in 67 of the idiopathic cases (33%). Local pathology or the leading point precipitating intussusception was found in 27 cases (12%); there were eight benign tumors, six malignant tumors, and 13 tumor-like lesions. In 32 of the 33 cases in adults, there was a definite contributing pathologic entity, including 18 benign tumors, 11 malignant tumors, and three tumor-like lesions. In infants and young children, there is usually no apparent predisposing disease, and a contributing or causative local pathologic lesion is seldom found. In contrast, intussusception in adults is almost invariably caused by some preexisting lesion involving the bowel wall. Furthermore, trauma, lymphoid hyperplasia, pregnancy, and viral infection may be possible predisposing factors in the production of intussusception.

Control of IgE responses

Peyer's patches (PP) in germ-free rats (GF) and in the hyper-IgE syndrome patient (HIES) differ from their conventional rat (C) and healthy human (HH) counterparts in that GF rats contained fewer (two-fold) PP and none was detected in HIES. Existing PP in GF rats had reduced cellularity (three-fold) and different B and T cell subsets: high numbers of IgE-bearing (sIgE+) B cells (approximately 15% of total cells), one-half of which also expressed sIgA, were present in GF rat PP while none was detected in C rat PP (less than 1%). GF rat PP also contained elevated numbers of sIgA+ cells and decreased sIgM+ cells, with elevated numbers of sThy 1+ RT 7.1+ Ig- T cells (suppressor phenotype) and reduced sThy 1- RT 7.1+ Ig- T cells (helper phenotype). The cellular composition of GF rat PP was converted to that resembling a C rat within 18 hr after (a) use of standard (unautoclaved) chow; (b) feeding with certain bacteria or "working" bacterial cell wall components (BCWC) and synthetic derivatives, murein, MTP-PE, and norMDP, but not with LPS, core lipid A, or lipoprotein; BCWC had no effect if injected intravenously; or (c) thymectomy. Each procedure resulted in (i) elimination of sIgE+ B cells and normalization of the other isotypes, and (ii) loss of T suppressor cells and normalization of T helper cells. After treatments, no sIgE+ cells were detected in bone marrow (BM), thymus, other lymphoid organs, or blood. PP were not detected in HIES, although they were present in HH (approximately 10/individual). P blood contained two distinct sIgE+ B cell subpopulations, the apparent source of which was mesenteric lymph node (MLN), the only organ in which high numbers of these cells (35%) (five nodes examined) were detected; far fewer IgE+ cells were found in spleen (less than 5%), and none was detected in BM, thymus, other LN, or appendix, which was virtually acellular. Virtually no IgE secreting plasma cells were detected in MLN, spleen, appendix, other lymphoid organs, or in gut lamina propria. IgE+ B cells in MLN were not detected in follicles (classical B cell areas); instead, they were found in high numbers in the thymus-dependent area and in medulla. Most follicles (greater than 98%) in MLN and spleen contained intercellular IgE complexed to bacterial antigen and/or CD23 (IgE-binding factor? antigen?), but contained no germinal centers.(ABSTRACT TRUNCATED AT 400 WORDS)

Leukemic cell-endothelial cell interactions in leukemic cell dissemination

In some human and experimental leukemias and lymphomas, the pattern of metastasis can be correlated with the homing sites of the normal progenitor cells. In vitro binding assays and homing experiments with murine lymphoma cell lines suggest that the nonrandom distribution of metastasis could be determined by specificity of cell-endothelium binding. A single subcutaneous inoculum of L2C cells in strain II guinea pigs resulted in a predictable stereotyped pattern of metastasis. Leukemic cell infiltrates were mainly observed around veins at specific locations in each organ: in brain, the most superficial leptomeningeal veins; in liver, veins of the portal triads; in lung, peribronchial veins; in kidney, veins of the renal columns; in adrenal gland, capsular veins and veins of the medulla. Those vessels also showed intense leukemic cell binding and diapedesis. This would suggest that the leukemic infiltrates were the result of transvenular traffic in these regions. Because leukemic cells were both in the intra- and extravascular compartments, the direction of the cell migration could not be determined. When L2C cells were injected into the right auricle of normal guinea pigs, leukemic cell binding occurred almost exclusively in veins located in areas of metastasis predilection. In addition, extravasation by diapedesis occurred in high endothelial venules in lymphoid organs, peribronchial veins and veins in the portal triads. Neither leukemic cell binding nor diapedesis occurred at the sinusoidal or capillary levels; extravasation in these vessels results from intravascular proliferation and secondary damage of the vessel wall, not by diapedesis. Our data suggest the existence in several organs of the guinea pig of a widely distributed, yet discrete, system of venular endothelial cells specialized in the traffic of leukemic cells.

Age-related changes in the morphology and immunophenotype of spontaneous lymphomas of SJL/N mice

Forty-four SJL mice were killed at intervals to follow the spontaneous development of lymphomas. These were detected in 28 of 38 mice aged 24 weeks or more. Immunoperoxidase stains were applied on cryostat sections of lymphomas from various sites (spleen, mesenteric lymph nodes, Peyer's patches, and other lymph nodes), sampled from 19 mice of different age groups, to study tumour immunophenotype in correlation with histological features. With a panel of antibodies against Thy 1.2, Lyt 1, and Lyt 2, and the mouse immunoglobulin heavy and light chains, all the 19 tumours were shown to be B-cell derived. This was further supported by the detection of Ia antigens on the tumour cells. Six mice had plasmacytoid or predominantly plasmacytoid tumours expressing gamma kappa. Three mice had mixed plasmacytoid and pleomorphic tumours which also showed gamma kappa positivity. The ages of these nine mice ranged from 24 to 44 weeks with a median of 36 weeks. Pleomorphic tumours were found in ten mice (age range = 36-52 weeks, median = 44 weeks). These tumours were more heterogeneous, expressing either alpha, mu, or gamma, or with loss of heavy chain expression altogether. These age-related changes are probably a sign of progressive loss of differentiation in B lymphomas.