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Experiments were designed to examine the wound healing characteristics at the aorta-endograft interface. Thoracic aneurysms were induced in sheep and excluded by endovascular placement of a selfexpanding stent graft (Corvita Endovascular Graft). After a follow-up of 1, 4, or 12 weeks sheep were sacrificed and the corresponding segments of the aorta were subjected to histological examinations. Histomorphological evaluation of all groups underlined sufficient exclusion of lesions of the aortic wall by endovascular grafting. There was no evidence of proximal or distal leakage, graft dislocation or migration. The results appeared to be evidence that the endoluminal stent graft may be incorporated by the host aortic tissue.

To elucidate the role of T lymphocytes in primary infection with Yersinia enterocolitica, we investigated the elimination rate of this pathogen, the histomorphology of tissue lesions, and the immune responses of athymic T-cell-deficient C57BL/6 nude mice and their euthymic littermates after parenteral infection with Y. enterocolitica of serotype O:8. While a low inoculum of 3 x 10(2) Y. enterocolitica cells (about 0.01 times the median lethal dose for normal C57BL/6 mice) was cleared by normal C57BL/6 mice within 7 to 10 days, athymic nude C57BL/6 mice developed progressive infections after this inoculum, leading to death on days 20 to 25 postinfection (p.i.). While normal C57BL/6 mice experienced short-term transient infections, nude mice exhibited a biphasic, progressive infectious process. Thus, in the early phase (days 1 to 7 p.i.), a rapid influx of CD11b/18-positive cells (Mac-1 antigen) and natural killer cells was evident in the spleens and livers of the nude mice. The late phase (from day 8 p.i. onward) was characterized by a rapid progression of the infection and a further influx of CD11b/18-positive cells into the liver accompanied by an increase in bacterial counts and development of tissue lesions particularly in the liver and spleen. In normal mice, granuloma-like lesions composed of CD11b/18-, CD4-, and CD8-positive cells could be observed. However, granulomata were not found in nude mice. Yersinia-specific immunoglobulin G antibodies appeared on day 15 p.i. in the sera of normal mice, while nude mice failed to develop significant antibody titers. Adoptive transfer of Yersinia-specific T cells into athymic nude mice mediated resistance to Y. enterocolitica infection and restored both the ability of granuloma formation and the production of specific antibodies. In summary, the data presented herein strongly suggest that T lymphocytes play an essential role in the defense of C57BL/6 mice against Y. enterocolitica.

This paper is a survey of the histomorphology of experimental listeriosis based on cooperative studies performed within the past ten years. The influence of various parameters of the infectious agent (pathogenic Listeria monocytogenes serovar 4b, nonpathogenic Listeria innocua serovar 6b etc.) as well as of the host (euthymic NMRI-mice conditioned with dextran sulfate 500 or cyclosporin A, athymic nude mice etc.) on the course, morphology and outcome of the Listeria infection was investigated. From the experimental models used and the studies performed much could be learned concerning the factors that determine the histomorphological manifestations of listeriosis in humans.

Experimental listeriosis in phenotypically normal (nu/+) euthymic NMRI mice has a characteristic morphology and short-term course. In contrast, listeric infection in congenitally dysthymic nude (nu/nu) mice does not proceed in clear-cut phases, develops more slowly, displays a chronic tendency from the beginning, and shows a considerably different morphology. The inability of nude mice to effectively control and terminate infection by Listeria monocytogenes obviously results from the lack of T lymphocytes.

NMRI mice were experimentally infected with Listeria monocytogenes serotypes 1/2b, 3a, 4b, and 4d and Listeria innocua serotype 6b by different means. The course of infection was monitored, using bacteriological and histological methods. The following typical features of experimental infection with the various L. monocytogenes and L. innocua serotypes were observed. (i) On the basis of the mean lethal dose, L. monocytogenes 4b, 4d, and 1/2b proved to be mouse pathogenic, although to different degrees, L. monocytogenes 3a and L. innocua can be regarded as nonpathogenic for NMRI mice. The virulence of L. monocytogenes serotype 4d was increased 1,000-fold after adaptation to mice. (ii) Primary infection with any serotype of L. monocytogenes or L. innocua resulted in protection against a lethal challenge with the most virulent serotype, 4b. This protective immunity could be transferred by spleen cells. Compared with the duration of immunity achieved by infection with L. monocytogenes serotype 4b, the protection induced by infection with L. innocua was short lived and dose dependent. The data obtained also suggest that immunity after experimental infection with any serotype of L. monocytogenes or L. innocua is produced only when the animal host is filled with bacteria. (iii) The distribution of the germs in the internal organs of the mouse shortly after infection was dependent on the route of infection rather than on the serotype used. (iv) The main difference among the Listeria serotypes tested was their ability to multiply within the host and to induce a granulomatous inflammation. The results indicate that mouse pathogenicity and virulence of Listeria spp. cannot be defined only by the capacity of the bacteria to infect or kill conventional mice. Such a definition should include an analysis of the immune system of the host, a kinetic study of experimental infection, and a histomorphological evaluation of the lesions induced.

Although the parenteral injection of dextran sulfate 500 (DS 500; 50 mg/kg body weight) into 22-month-old NMRI mice resulted in a complete loss of resistance when administered 1 day before the sublethal (4.5 X 10(3)) infection with Listeria monocytogenes, the consequences in aged animals were less dramatic than in young adult (2- to 3-month-old) controls. This was documented by prolonged survival times as well as reduced numbers of Listeriae in spleen. This indicates that aged mice possess an increased paghocytic capacity, as compared to young adult animals. In aged mice the DS 500-induced loss of resistance could be completely abolished by pretreatment with 3 X 10(9) heat-killed Bordetella pertussis organisms 4 days before the DS 500 injection, i.e., 5 days before listeric infection. This indicates that aged NMRI mice possess remarkable reserves in phagocytic activity.

Summary Unlike the acute and short-term course of experimental listeriosis in phenotypically normal (nu/+) mice, Listeria monocytogenes infection in conventionally raised athymic Nude mice results in chronic inflammation with persistence of bacteria and lesions in the internal organs such as liver and spleen. Although it could be shown that germfree Nude mice had no intestinal microbial flora and lacked measurable serum immunoglobulins, neither the course nor the histomorphology of experimental listeriosis, differed significantly from that of their conventionally raised littermates. The results indicate that the typical response of Nude mice to Listeria infection is primarily determined by inborn factors and not by prior antigenic stimulation.

Parenteral injection of dextran sulfate 500 (DS 500; 50 mg/kg of body weight) into mice caused a complete loss of resistance to a sublethal (2 X 10(3) to 5 X 10(3)) infection with Listeria monocytogenes. Such loss could be prevented by pretreatment of animals with 3 X 10(9) heat-killed Bordetella pertussis organisms (PO) 5 to 30 days before the administration of DS 500. The increased phagocytic capcity induced by PO was only exhausted when a fourfold dose of DS 500, effecting complete loss of antibacterial resistance (50 mg/kg ob body weight), was administered. Listeriosis in mice treated with DS 500 is characterized by rapid-progressive necro-purulent inflammation of liver and spleen, lack of mononuclear phagocyte response, and 100% lethality within 72 h after infection. In contrast, the time course, extent, and morphological characteristics of listeriosis in animals pretreated with PO before the DS 500 application were not significantly different from those of nonpretreated controls. Evidence is presented that the protective effect of PO is due to activation of the mononuclear phagocyte system, which without such treatment is blocked by the DS 500 administration. The data presented indicate that the protective effect of PO is due only in part to the endotoxic moiety of these bacteria. Differences in the course and morphology of listeriosis in animals with dysfunction of the mononuclear phagocyte system and in animals with deficiency of the cellular immune system are discussed.

A brief survey on the ultrastructure, the chemical composition and the immunological properties of bacterial cell wall peptidoglycan (mucopeptide) is presented. This paper deals with the various recently discovered biological activities of peptidoglycan. These could be divided into three different groups, namely: 1. Endotoxin-like properties: pyrogenicity, induction of the local Shwartzman reaction, increase in non-specific resistance to bacterial infection, release of 5-hydroxytryptamine from rabbit platelets, complement activation,gelation of amebocyte lysate. 2. Inflammatory reactions of skin and internal organs, aggressin activity (virulence factor), inhibition of phagocytosis of bacteria by granulocytes and macrophages, inhibition of growth of cell cultures, cytotoxity to granulocytes and macrophages. 3. Potentiation of humoral and cellular immune responses (adjuvant), enhancement of tumor defense in experimental animals. The potential mechanisms of action of peptidoglycan are discussed and attention is focused on the implications of the various peptidoglycan activities for medicine.

By the use of various experimental procedures with rats, the significance of intraluminal hypertension, caused by ductal obstruction, reflux of bile and duodenal reflux were considered with regard to their capacity for producing pancreatitis. The extent of the histological changes in the pancreas after 48 hours as well as the period of survival in the individual experimental groups served as the parameters for the comparison. The results show that the rise in intraluminal pressure is alone enough to produce acute pancreatitis. It follows from this that rise of pressure in the duct system caused by ductal obstruction may be the triggering factor in the induction of pancreatitis. Reflux of bile, bacterial colonisation of the pancreas by duodenal reflux as well as activation of proteolytic enzymes were not necessary a prior factors but ones which have an aggravating effect in the development of the disease.

A study was performed to find out whether or not RNA and DNA isolated from Group A streptococcal cytoplasm does possess adjuvant activity. The findings obtained indicate that the adjuvancy of streptococcal RNA is very similar to that of poly I:C. The adjuvant activity of poly I:C is characterized by its capacity to increase the number of pre-existing hemolysin-producing spleen cells and by its ability to increase the development of 19S and 7S producers early in the 12-day-period of primary immune response. The adjuvancy of streptococcal DNA was considerably less pronounced than that of RNA. Neither poly I:C nor streptococcal RNA and DNA were found to be capable of increasing the process of priming for the secondary immune response.

Every inflammation has its morphological substrate, however, not every morphological substrate is specific for a particular disease. On one side, this is due to the limited reaction spectrum of the organism, on the other side, to the fact that completely different etiological agents are able to activate the same pathomechanism. Since this holds true for granuloma formation also, the term "specific inflammation" has to be restricted considerably today. On the other hand, recent progress in the field of mediators of inflammation frequently permits a pathogenetic classification of granulomatous inflammatory processes - even before the etiology has been clarified (e.g. Morbus Boeck). In addition, the possibility to identify "granuloma cells", in particular macrophage- and lymphocyte-subpopulations, in situ by immunohistological means (by monoclonal antibodies to surface markers) expands the scope of conventional histomorphological techniques significantly.

The binding of the synthetic immunoadjuvant N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP, for muramyl dipeptide) to human and rabbit sera containing peptidoglycan (PG) antibodies was investigated. Studies were performed by employing the corresponding 14C or 125I-labeled compounds in Farr-type binding and inhibition assays. Whereas MDP did not react with naturally occurring or experimentally induced PG-antibodies, the analog of MDP MDP-L-Lys-D-Ala did bind to hyperimmune rabbit anti-PG sera, but not to the human sera tested. These studies indicate that the radioimmunoassays employed basically are applicable for the selection of nonimmumogenic MDP analogs possessing immunoadjuvant activity.

This review deals with those biological activities of peptidoglycan that are not directly analogous to the properties of gram-negative bacterial endotoxin. The report is divided into 3 major parts: 1. A survey of peptidoglycan activities such as the induction of inflammatory skin reactions, lesion-enhancing activity (virulence factor), inhibition of phagocytosis of bacteria, inhibition of cell migration, cytotoxicity to mammalian cells, potentiation of the humoral and cellular immune response (adjuvant activity) and enhancement of tumor defense in experimental animals. 2. A presentation of factors which may influence these biological activities of peptidoglycan. 3. A brief discussion of the potential mechanisms of action of peptidoglycan.

The gelation of a lysate prepared from the amebocytes of Limulus polyphemus, the horseshoe crab, has been used to detect endotoxin-like material in clinical studies and in "in vitro" experiments. The investigation of blood samples from 54 hospitalized patients suspected of having endotoxemia, revealed a positive limulus test in 14. Infections due to gram-positive organisms were not associated with positive assays. These results were in agreement with the observation that living gram-positive microorganisms - in contrast to gram-negative bacteria - did not initiate lysate gelation when studied "in vitro". Only very high concentrations of peptidoglycan, isolated from the cell walls of various gram-positive bacteria, induced the reaction. Therefore, these findings support the view, that the limulus test is relatively specific for the detection of gram-negative bacterial endotoxin and endotoxemia.

A major portion of the humoral immune response to peptidoglycans is directed against the non-cross-linked pentapeptide side chains of these ubiquitous bacterial antigens. At present, no specific and sensitive assay for pentapeptide antibody determination is available. Therefore, a radioimmunoassay has been developed which employs the synthetic pentapeptide hapten L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala, labeled by the active ester method of Bolton and Hunter to high specific activities (6.74 to 18.18 muCi/mug) with 125I, and used as a reagent for measuring pentapeptide antibody. A-variant streptococcal antisera, known to contain pentapeptide antibodies as shown by quantitative precipitation, would bind more than 95% of the radiolabeled hapten in contrast to 2 to 3% by preimmune rabbit sera. Specificity of the binding reaction was demonstrated by inhibition experiments imploying various synthetic oligopeptides related or unrelated to the pentapeptide in the radioimmunoassay. Binding curves established with serial dilutions of peptidoglycan antiserum were linear from 15 to 500 mug/ml of antibody permitting pentapeptide antibody measurement within this range. Comparative data on pentapeptide antibody determinations by quantitative precipitation and radioimmunoassay are given and the time course of the production of this antibody in 14 rabbits hyperimmunized with A-variant streptococcal vaccine is reported.

By application of immunohistological methods in experimental alveolar echinococcosis, detailed information was obtained on the antigenic properties of each component of the echinococcus cyst. It was established that of the various layers, the capsula germinativa of the parasite cyst possesses the strongest antigenicity regardless of localization and maturity of the cysts. The dissemination of echinococcal antigens within the internal organs of the experimental animals was found to follow the general trends of other infections. Substances obtained from the capsula germinativa appear most suitable as reagents for immunodiagnostic purposes due to their strong antigenicity.

In the present paper, morphologic studies on experimental echinococcosis are reported. Following i.p. infection of gerbils (Meriones unguiculatus) with Echinococcus multilocularis scolices, the development of cysts within the internal organs of the experimental animals could be readily visualized by scanning electron microscopy.

The influence of complement system in acute pancreatitis in the rat was examined. Two different experimental procedures were used to induce pancreatitis: distal choledochal ligature and the Pfeffer model as modified by NEVALAINEN. In both procedures an acute pancreatitis developed and complement depression was noted. These results showed that consumption of complement will occur even in pancreatitis induced by other than immunologic models. In a second series the same experimental procedures were used in rats that had been decomplemented by application of cobra venom factor. It was possible to produce an acute pancreatitis of moderate severity.

Two different experimental procedures were used to induce pancreatitis in rats: distal ligature of the common bile duct and the Pfeffer method in modification of Nevalainen. It could be shown that consumption of complement can be demonstrated even in pancreatitis induced by other than immunological models. Further examination in decomplemented rats showed the possibility of inducing acute pancreatitis by the above-mentioned models, although of less intensity. Therefore, the complement system will be an important factor for the progress and intensity of the inflammation process.

Previous studies have shown that peptidoglycans from group A and B streptococci inhibit the migration of peritoneal exudate cells from non-sensitized rats and guinea pigs. In the present studies peptidoglycans from S. aureus and S. epidermidis were found to inhibit the migration of cells to the same extent as group A streptococcal peptidoglycan. In contrast, HSA-pentapeptide, an immunologically active synthetic analog of the peptide moiety of peptidoglycan which is free of the intrinsic toxicity of naturally occurring peptidoglycans, did not induce migration inhibition of peritoneal exudate cells from non-sensitized guinea pigs. Sensitization of animals with 200 mug HSA-pentapeptide emulsified in incomplete Freund's adjuvant significantly reduced the inhibitory effect of streptococcal and staphylococcal peptidoglycan; HSA-pentapeptide again showed no activity. However, when HSA-pentapeptide was tested against cells from animals sensitized with 200 mug HSA-pentapeptide incorporated in complete Freund's adjuvant, a strong inhibition of migration was evident. Skin tests performed in these animals, in contrast to the dermonecrotic reaction elicited by streptococcal or staphylococcal peptidoglycan, revealed a characteristic delay hypersensitivity to HSA-pentapeptide.

Hepatic granulomas were induced in mice by injection of blastospores, cell walls, and glucan of Candida albicans. Granulomatous reactions in liver tissue initially multiplied but later decreased. A dose-response relationship was apparent with up to 3 mg of inoculum. Shortly after injection of C. albicans spores, fungal elements appeared in liver macrophages and were detectable in granuloma and Kupffer cells for 20 days. Gram-stain, periodic acid-Schiff (PAS), and immunofluorescence reactions soon vanished, and the organisms could no longer be seen. Glucan of C. albicans, which lacked PAS and immunofluorescence reactivity, proved active in initiation of granulomas. Degradation of phagocytized spores of C. albicans, reductions of cytoplasm, and cell wall deformation and collapse support the premise that loss of PAS and immunofluorescence reactivity was caused by enzymatic breakdown of candida cell wall mannan in macrophages. We conclude that C. albicans can induce granulomatous reactions in mouse liver when the glucan that forms the cell wall matrix in Candida persists in identifiable residues.

The secondary antibody-forming potential of non-splenic lymphatic tissues during senescence was investigated in NMRI/Han mice, both at the cellular and humoral levels. The mean life span of conventionally reared NMRI/Han mice amounts to 19.86 months. After primary immunization of aged (20-month-old) NMRI mice with 4 X 10(8) sheep erythrocytes (SE) by the intraperitoneal (i.p.) route, the primary antibody-forming potential of both spleen and lymph nodes was significantly reduced, as compared to young adult (3-month-old) controls. In contrast, the anamnestic response elicited by an i.p. booster injection of 4 X 10(8) SE at the 44th day after primary immunization was not significantly diminished in comparison to the controls. When killed cells of Bordetella pertussis were found to be significantly increased in young adult as well as in aged mice. These data obtained at the cellular level were in accordance with corresponding serological findings. The impressive restitution of the antibody-forming potential evident after secondary antigenic stimulation was associated with a remarkable restitution of the lymph node morphology. This was particularly pronounced in the pronounced in the parathymic lymph nodes which represent the draining nodes for the peritoneal cavity. These findings indicate that the lymph nodes of the senescent individual also possess remarkable reserves in immunocompetence.