Localized gut-associated lymphoid tissue hemorrhage induced by intravenous peptidoglycan-polysaccharide polymers

Anterior chamber-associated immune deviation: a review of the anatomical evidence for the afferent arm of this unusual experimental model of ocular immune responses

Anterior chamber-associated immune deviation (ACAID) is an animal model of tolerance induced experimentally by the injection of antigen into the anterior chamber of the eye. The unusual deviant immune response has both afferent and efferent arms and it is the former that is the focus of this review. The paradigm states that antigen injected into the anterior chamber of the eye is internalized by intraocular antigen presenting cells (APCs) which then migrate largely to the spleen to induce the differentiation of regulatory T cell populations which in turn form the basis of the modified efferent arm to the deviant immune response. However, the migration routes of ocular APCs or free antigen to the secondary lymphoid organs remain unclear. In this review we will discuss the evidence for different possible afferent routes by which antigen (either free or cell-associated) leaves the eye and the pattern of distribution to secondary lymphoid organs.

Colitis in HLA-B27/beta 2 microglobulin transgenic rats

Rats of susceptible genetic backgrounds expressing high copy numbers of the transgene encoding HLA-B27 and human beta 2 mu develop chronic colitis complicated in the advanced stage by adenomatous polyps progressing to adenocarcinoma. Unique features of this model include a spectrum of extraintestinal manifestations resembling to some extent human spondyloarthropathy, with peripheral and axial joint, dermatologic and male genital inflammation. Inflammation is T lymphocyte mediated, although surprisingly CD4+ cells are more active in transferring disease than CD8+ cells, which would be expected to be preferentially activated by Class I MHC peptides. Inflammation is dependent on a nonlymphoid bone marrow-derived cell, expressing high copy numbers of B27, probably APCs. In vitro function of transgenic dendritic cells is deficient, and in vivo competition for peptide binding in the antigen binding site of B27 attenuates arthritis. Normal bacteria are required for disease expression, with B. vulgatus preferentially able to induce colitis, whereas other bacteria such as E. coli stimulate no inflammatory response. Inflammation and resulted complications are modulated by non-MHC genes and are amenable to treatment by bone marrow transplant from normal donors. These results support the hypothesis that gastrointestinal and systemic inflammation in B27 transgenic rats is the result of loss of tolerance to enteric bacteria, as a consequence of defective APC (? dendritic cells) function. Whether disease is the result of selective MHC binding of enteric antigens uniquely capable of inducing disease, lack of appropriate induction of a CD8+ suppressor cell population, or skewed cytokine (IL-12, IL-18) secretion by APCs remains to be determined.

Detection of peptidoglycan in human plasma using the silkworm larvae plasma test

Silkworm larvae plasma (SLP) reagent, which is prepared from the body fluid of the silkworm, reacts with peptidoglycan (PG), a fragment of both the Gram-positive and Gram-negative bacterial cell wall, as well as with beta-glucan, a component of fungi. We developed a quantitative method for the detection of PG in human plasma from cases with bacterial infection using the SLP reagent. Tested in this way, the SLP method showed 86.2% sensitivity, 90.6% specificity, 89.3% positive predictive value, and 88.5% efficiency. The SLP method provides a valuable tool for the diagnosis of systemic infection using patients' blood.

Petechial hemorrhages in the small intestinal Peyer's patches: a new manifestation of systemic anaphylaxis

Systemic anaphylaxis in the rat has major manifestations in the small intestine. In August rats, but not in other strains, intestinal anaphylaxis was accompanied by petechial hemorrhages in Peyer's patches. The occurrence of petechiae was not proportional to the intensity of prostration, cyanosis or gut congestion. No hemorrhages were found in other organs. The petechiae occurred in August rats of either sex after sensitization and challenge with any of several antigens and adjuvants and after passive sensitization with antiserum. The number of Peyer's patches with hemorrhage varied from one to all 20 in individual rats. The occurrence of petechiae was not influenced significantly by the route of sensitization or challenge, by the presence or absence of pinworms in the cecum, or by ancillary treatment at time of challenge with normal serum, normal blood, heparin, pertussis vaccine or lipopolysaccharide. The intestinal mast cells of the susceptible August rats were not different from the mast cells of the resistant strains. Furthermore, mast cells did not reside in the lymphoid follicles of Peyer's patches which was the site of the petechial hemorrhages in anaphylactic August rats. Nor did injections of histamine, serotonin or both cause hemorrhages in Peyer's patches.

The consequences of the intracellular retention of pathogen-derived T-cell-independent antigens on protein presentation to T cells

Intracellular pathogens can be considered as particulate antigens chemically composed of a complex mixture of T-cell-dependent antigens (TD) (peptides and proteins) and T-cell-independent antigens (TI) (glycolipids and complex polysaccharides). A large range of saccharides (from oligosaccharides to complex polysaccharides) derived from pathogenic microorganisms are being isolated and characterized. They are currently implicated in signaling systems and concomitant host-parasite relationships. However, there are not many structure-function relationships described for these pathogens. This is particularly true of polysaccharides. In this report we have reviewed the role of defined TI antigens in the processing and presentation of defined TD antigens to specific T cells by antigen-presenting cells (APC). We also considered the importance of some of the chemical characteristics shared by different carbohydrates implicated in the inhibition of antigen presentation. These findings are discussed in relation to the clear immunopathological consequences of long retention periods of complex carbohydrate molecules derived from intracellular parasites inside certain APC and the absence of antigen presentation impairment in physiological situations such as the removal of senescent or damaged red blood cells by splenic macrophages or intracellular accumulation of carbohydrates in colostrum and milk macrophages during lactation.

Phlogistic properties of peptidoglycan-polysaccharide polymers from cell walls of pathogenic and normal-flora bacteria which colonize humans

PG-PS polymers which can induce experimental chronic inflammation in joints and other tissues can be isolated from the cell walls of human pathogens, such as group A streptococci, as well as from certain indigenous bacterial species which colonize the human intestinal tract. The structural and biological properties that are required for cell wall fragments to express this remarkable activity are still not well defined, but polymer size, resistance to tissue enzymes, and capacity to sustain activation of complement, macrophages, neutrophils, and T cells are properties associated with the most active preparations. There is increasing evidence that PG-PS structures with arthropathogenic activity occur in the human intestinal lumen and that these polymers can be translocated systemically. These observations support the concept that PG-PS, derived from a variety of bacterial species, can be part of the etiology of rheumatoid arthritis and other chronic inflammatory diseases. Since the PG component provides a common element to which all individuals are exposed, it follows that susceptibility is related to efficiency of disposal of bacterial cell wall debris, as well as to cytokine networks and immune cell function (51).

Protracted anemia associated with chronic, relapsing systemic inflammation induced by arthropathic peptidoglycan-polysaccharide polymers in rats

Mild hypoproliferative anemia with abnormal iron metabolism frequently accompanies chronic inflammation and infection in humans. To determine whether anemia is associated with chronic relapsing arthritis induced by bacterial cell wall polymers, serial determinations of the hematocrit were measured in rats injected intraperitoneally with sonicated peptidoglycan-polysaccharide fragments from group A streptococci. Acute anemia peaked 5 to 10 days after injection, and chronic, spontaneously relapsing anemia persisted for 309 days. 51Cr labeling demonstrated decreased erythrocyte survival, i.e., a half-life of 8.4 days in cell wall-injected rats versus 11.8 days in controls. Erythrocytes were mildly microcytic, and leukocyte counts were elevated during early spontaneous reactivation of arthritis, 15 days after injection of peptidoglycan-polysaccharide. Bone marrow myeloid/erythroid precursor ratios were elevated in arthritic rats (P less than 0.0001). Purified peptidoglycan produced an acute anemia lasting 10 days, while injection of group A streptococcal polysaccharide and mutanolysin-digested cell wall did not affect the hematocrit. The minimal effective dose of peptidoglycan-polysaccharide was 5 micrograms of rhamnose per g (body weight). Serum iron and transferrin levels were decreased in cell wall-injected rats (P less than 0.005) and were closely correlated with hematocrit values and joint inflammatory scores. Stainable iron was increased in the liver, spleen, and mesenteric lymph nodes and unchanged in the bone marrow of cell wall-injected rats. Anemia accompanying chronic, relapsing systemic inflammation induced by peptidoglycan-polysaccharide polymers appears to be an excellent animal model of the anemia of chronic disease.

Eicosanoid regulation of acute intestinal vascular permeability induced by intravenous peptidoglycan-polysaccharide polymers

A model of rapidly developing, self-limited acute vascular permeability changes localized to the gut-associated lymphoid tissue (GALT) of the rat was used to study the role of prostaglandins (PGs), thromboxanes (Txs), and leukotrienes (LTs) in the in vivo regulation of early intestinal inflammatory events. Sprague-Dawley rats were pretreated with metabolites, enzyme inhibitors, or receptor antagonists of the arachidonic acid pathway before intravenous injection of sonicated peptidoglycan-polysaccharide polymers derived from group A streptococci (PG-APS, 5 micrograms rhamnose/g body weight). Rats were killed five minutes after PG-APS injection and were evaluated grossly for petechiae of the intestinal parenchyma and lymphoid aggregates. Indomethacin or dexamethasone increased intestinal injury by PG-APS by inducing mid-small bowel and cecal parenchymal hemorrhage. Indomethacin significantly diminished colonic lymphoid aggregate hemorrhage. PGE1, PGE2, and prostacyclin dramatically inhibited GALT hemorrhage; prostacyclin was the most potent with an effective dose of 0.1 microgram/kg. Dazmegrel, a specific Tx synthetase antagonist, significantly inhibited PG-APS-induced vascular permeability. Dazmegrel continued to diminish colonic lymphoid aggregated hemorrhage during concurrent treatment with indomethacin, which removed potential endogenous prostaglandin protection. Diethylcarbamazine, a lipoxygenase inhibitor, and FPL-55712, a LT receptor antagonist, inhibited the PG-APS-induced lesions, with FPL-55712 being more potent. LT blockade had a predominant effect on the intestinal parenchymal hemorrhage. We postulate that the normal homeostatic suppression of inflammation induced by phlogistic bacterial cell wall polymers is PG mediated, and that pathological responses are Tx and LT dependent.

Immune complex-induced enteropathy. Effects of repeated injections of immune complexes on the small intestine of the rat

Rats injected intravenously with immune complexes (IC) prepared in 5x antigen excess were reported previously to develop a distinctive striped pattern of serosal hyperemia of the small intestine accompanied by mucosal edema and hemorrhage. This study tested the effect of repeated injections of IC given at 3-day intervals. After the last of four, six, or nine injections, rats continued to show the same gross and histologic lesions observed in rats injected once with IC. After serial injections, however, the distal small intestine was more severely involved than the proximal intestine. In addition, villous shortening, stromal hemosiderin deposits, and gut-associated lymphoid tissue and mesenteric lymph node sinus hemorrhage and hemosiderin deposits were seen in rats given nine injections. There was a remarkable absence of stromal infiltration of the villi by inflammatory cells. Experiments conducted with 125I-labeled IC plus sufficient "cold" IC to induce intestinal lesions showed that IC were deposited at extravascular sites in the gut. The failure of such IC to provoke cellular infiltration in the gut is unexplained.