Leukocyte receptor expression in chronic periodontitis.

BACKGROUND AND OBJECTIVE: Microbial recognition in the periodontium through specific leukocyte receptors gives rise to the response which in susceptible individuals can lead to periodontal diseases. The aim of this study was to explore the expression of leukocyte receptors in the gingival tissues of chronic periodontitis patients and to analyse differences between diseased and control sites (sites with probing pocket depth <4 mm). MATERIAL AND METHODS: Thirty-seven chronic periodontitis patients were included in the study. Gingival biopsies were harvested from diseased and control sites and processed by flow cytometry for the determination of the expression of 16 leukocyte receptors (CD4, CD8, CD11b, CD14, CD16, CD19, CD25, CD28, CD49d, CD49e, CD62, CD71, CD80, CCR7, Ly6G and HLA-DR). RESULTS: Expression of all studied receptors was higher in test compared with control sites (p < 0.005). Sampled sites with less bleeding on probing exhibited higher expression of CD16 and CD14 receptors (p = 0.020 and 0.011, respectively). CONCLUSIONS: This study points towards considerable differences in the expression of leukocyte receptors between diseased and control sites in the same periodontal patients.

Dynamics of in silico leukocyte rolling, activation, and adhesion.

BACKGROUND: We present a multilevel, agent based, in silico model that represents the dynamics of rolling, activation, and adhesion of individual leukocytes in vitro. Object-oriented software components were designed, verified, plugged together, and then operated in ways that represent the molecular and cellular mechanisms believed responsible for leukocyte rolling and adhesion. The result is an in silico analogue of an experimental in vitro system. The experimentally measured, phenotypic attributes of the analogue were compared and contrasted to those of leukocytes in vitro from three different experimental conditions. RESULTS: The individual in silico dynamics of "rolling" on simulated P-selectin, and separately on simulated VCAM-1, were an acceptable match to individual in vitro distance-time and velocity-time measurements. The analogues are also able to represent the transition from rolling to adhesion on P-selectin and VCAM-1 in the presence of GRO-alpha chemokine. The individual in silico and in vitro behavioral similarities translated successfully to population level measures. These behavioral similarities were enabled in part by subdividing the functionality of the analogue's surface into 600 independent, "cell"-controlled, equally capable modules of comparable functionality. CONCLUSION: The overlap in phenotypic attributes of our analogue with those of leukocytes in vitro confirm the considerable potential of our model for studying the key events that determine the behavioral outcome of individual leukocytes during rolling, activation, and adhesion. Our results provide an important foundation and framework for future in silico research into plausible causal links between well-documented, subcellular molecular level events and the variety of systemic phenotypic attributes that distinguish normal leukocyte adhesion from abnormal disease-associated adhesion.

The pancreatic islet endothelial cell: emerging roles in islet function and disease.

The pancreatic islets are one of the most vascularized organs of the body. This likely reflects the requirements of the organ for a rich supply of nutrients and oxygen to the tissue, as well as the need for rapid disposal of metabolites and secreted hormones. The islet endothelium is richly fenestrated to facilitate trans-endothelial transport of secreted hormones, has a unique expression of surface markers, and produces a number of vasoactive substances and growth factors. The islet endothelial cells play a critical role in the early phase of type 1 diabetes mellitus by increasing the expression of surface leucocyte-homing receptors, thereby enabling immune cells to enter the endocrine tissue and cause beta-cell destruction. Following transplantation, pancreatic islets lack a functional capillary system and need to be properly revascularized. Insufficient revascularization may severely affect the transport properties of the islet endothelial system, resulting in a dysfunctional islet graft.

Integrin CD11a cytoplasmic tail interacts with the CD45 membrane-proximal protein tyrosine phosphatase domain 1.

Leucocyte adhesion receptor integrin CD11aCD18 and the transmembrane receptor-like protein tyrosine phosphatase (RPTP) CD45 mediate immune synapse formation and signalling during antigen presentation. Previous cocapping studies on human naïve T cells demonstrate an interaction between CD11aCD18 and CD45. CD45 cross-linking also has an effect on the ligand-binding activity of CD11aCD18. However, the mode of interaction between CD11aCD18 and CD45 remains unclear. Herein, yeast two-hybrid analysis identified a partial CD45 cytoplasmic tail interacting with that of CD11a. The CD45 cytoplasmic tail comprises a membrane proximal (Mp) region, protein tyrosine phosphatase domain 1 (D1), spacer, D2, and carboxyl terminus. CD45 Mp-D1 was found to be the main interacting region for the CD11a cytoplasmic tail. In contrast, the full-length CD45 cytoplasmic tail interacted weakly with that of CD11a. It has been reported that CD45 Mp-D1 but not the full-length cytoplasmic tail forms a homodimer whose enzymatic activity is inhibited. Our in vitro binding and enzymatic assays showed that the homodimeric CD45 cytoplasmic tail interacts with that of CD11a. The biological function of CD45 dimerization and its association with CD11a remains to be investigated.

Polyunsaturated fatty acids interfere with formation of the immunological synapse.

Polyunsaturated fatty acids (PUFAs) exert inhibitory effects on T cell-mediated immune responses. Activation of T cells in vivo depends on formation of an immunological synapse (IS) at the T cell/antigen-presenting cell (APC) interface. Here, we analyzed effects of PUFA treatment on the formation of the IS and APC-induced human T cell activation. In T cells treated with the PUFA eicosapentaenoic (EPA; 20:5,n-3) and arachidonic acid (20:4,n-6), stimulated by superantigen-presenting cells or APCs, relocalization to the IS of distinct molecules [F-actin, talin, leukocyte functional antigen-1alpha, clusters of differentiation (CD)3epsilon] was inhibited markedly compared with cells treated with saturated fatty acid, whereas relocalization of protein kinase Ctheta to the IS remained unaffected. CD3-induced, sustained phosphorylation of nucleotide exchange factor Vav, which controls cytoskeletal rearrangements underlying IS formation, was significantly reduced in EPA-treated Jurkat and peripheral blood T cells. In addition, T cell raft disruption by methyl-beta-cyclodextrin treatment and experiments with a chimeric linker for activation of T cell proteins, which is resistant to PUFA effects on lipid rafts, revealed modifications of lipid rafts as a crucial factor for PUFA-mediated inhibition of APC-stimulated cytoskeletal rearrangements. Furthermore, the efficiency of T cell/APC conjugate formation was significantly reduced with EPA-treated T cells, as was stimulation of CD69 expression, which is not altered following antibody-mediated T cell activation. In conclusion, PUFA treatment of T cells qualitatively and quantitatively alters IS formation, thereby extending T cell signaling defects to pathways that are not intrinsically altered in PUFA-treated T cells when stimulated by antibodies.

Activation of complement and leukocyte receptors during on- and off pump coronary artery bypass surgery.

OBJECTIVE: The aim of this prospective, randomised study was to investigate the influence of extracorporeal circulation on the inflammatory response, our hypothesis being that off pump coronary artery bypass grafting (OFFCAB) procedures would generate less activation than on pump procedures (ONCAB). METHODS: Patients admitted for elective CABG were randomised to either ONCAB or OFFCAB surgery and blood samples were taken during and up to 24 h after the operation. We measured complement factors C5a and the terminal complement complex (TCC, C59-b), and the interleukins IL-6 and IL-8. Leukocytes were studied for cellular counts and adhesion molecules (CD11b, CD35 and CD62L) by flow cytometry. We included a combination of activity markers with different aspects of neutrophil function and combined these with in vitro activation. RESULTS: The complement factors C5a and TCC showed a more rapid (P=0.02, P<0.001) and TCC a more profound (P<0.001) increase in the ONCAB group than in the OFFCAB group during the operation, after that there were no inter-group differences. Cellular markers, cell counts and interleukin levels were activated by surgery but with no difference between groups. CONCLUSION: This prospective, randomised study showed less complement activation in low risk OFFCAB, compared to ONCAB patients.

Small molecule LFA-1 antagonists compete with an anti-LFA-1 monoclonal antibody for binding to the CD11a I domain: development of a flow-cytometry-based receptor occupancy assay.

The beta(2) integrin LFA-1 (CD11a/CD18) is a leukocyte-specific adhesion molecule that mediates leukocyte extravasation, antigen presentation, and T-cell-mediated cytolysis through its interaction with its counter-receptors, ICAM-1, ICAM-2, and ICAM-3. We have recently described a small molecule antagonist of LFA-1 (BIRT 377) that inhibits LFA-1/ICAM-1 molecular interactions, LFA-1-dependent adhesion assays, antigen-induced proliferation of T-cells, and superantigen-induced production of IL-2 in vivo in mice. We have also recently described a unique monoclonal antibody, R3.1, which competes with BIRT 377 and its analogs for binding to both purified full-length LFA-1 and the purified recombinant I domain module. In this manuscript, we extend these studies to cell-based systems and utilize this unique reagent for the development of a receptor occupancy assay. Exploiting these observations, we have designed and validated an assay that allows us to measure receptor occupancy in vitro on monkey and human peripheral blood leukocytes and ex vivo in whole blood from monkeys dosed with small molecule LFA-1 antagonists. Further refinement of these reagents has led to the development of a Fab-based assay that allows rapid and reproducible analysis of whole blood samples. These optimized reagents allow for quantification of the number of receptors expressed on the cell surface and a more accurate quantitation of receptor occupancy.

Functional relevance of activated beta1 integrins in mercury-induced nephritis.

Cell adhesion through different adhesion molecules is a crucial event in the inflammatory response. Integrins can only bind and mediate cellular adhesion after their activation by different specific stimuli. The state of beta1 integrin activation can be assessed by a group of monoclonal antibodies (HUTS) that selectively recognize beta1 integrins in their active form. A similar activated epitope in the rat was defined using the anti-human monoclonal antibody HUTS-21, which recognizes an activation-dependent epitope on the beta1 chain. It was found that the divalent cations Mn(2+) and Hg(2+) were able to induce in vitro the activation of beta1 integrins on rat lymphocytes. The Hg(2+) cation induces an autoimmune disease in the Brown Norway rat characterized by synthesis and glomerular deposits of anti-glomerular basement membrane antibodies, proteinuria, and interstitial nephritis. Using the mercury model of nephritis, it was found that the expression of HUTS-21 epitope is induced in vivo in rat lymphocytes, and its appearance is correlated with the other parameters at the onset of the disease. In addition, the administration of HUTS-21 monoclonal antibody to HgCl(2)-treated rats offered evidence of its protective effects (1) against infiltration of renal interstitium by leukocytes, and (2) in the reduction of anti-glomerular basement membrane synthesis and glomerular deposition. Nevertheless, urinary protein values remained unaffected. These results demonstrate a key role of beta1-activated integrins in both leukocyte cell-cell interactions and leukocyte infiltration pathway mechanism, and also indicate that leukocyte migration may have less importance in the development of this disease than previously thought.

Integrin-mediated neutrophil adhesion and retinal leukostasis in diabetes.

PURPOSE: A critical early event in the pathogenesis of diabetic retinopathy is leukocyte adhesion to the diabetic retinal vasculature. The process is mediated, in part, by intercellular adhesion molecule-1 (ICAM-1) and results in blood-retinal barrier breakdown and capillary nonperfusion. This study evaluated the expression and function of the corresponding ICAM-1-binding leukocyte beta2-integrins in experimental diabetes. METHODS: Diabetes was induced in Long Evans rats with streptozotocin. The expression of the surface integrin subunits CD11a, CD11b, and CD18 on rat neutrophils isolated from peripheral blood was quantitated with flow cytometry. In vitro neutrophil adhesion was studied using quantitative endothelial cell-neutrophil adhesion assays. The adhesive role of the integrin subunits CD11a, CD11b, and CD18 was tested using specific neutralizing monoclonal antibodies. CD18 bioactivity was blocked in vivo with anti-CD18 F(ab')2 fragments, and the effect on retinal leukocyte adhesion was quantitated with acridine orange leukocyte fluorography. RESULTS: Neutrophil CD11a, CD11b, and CD18 surface integrin levels were 62% (n = 5, P = 0.006), 54% (n = 5, P = 0.045), and 38% (n = 5, P = 0.009) greater in diabetic versus nondiabetic animals, respectively. Seventy-five percent more neutrophils from diabetic versus nondiabetic animals adhered to rat endothelial cell monolayers (n = 6, P = 0.02). Pretreatment of leukocytes with either anti-CD11b or anti-CD18 antibodies lowered the proportion of adherent diabetic neutrophils by 41% (n = 6, P = 0.01 for each treatment), whereas anti-CD11a antibodies had no significant effect (n = 6, P = 0.5). In vivo, systemic administration of anti-CD18 F(ab')2 fragments decreased diabetic retinal leukostasis by 62% (n = 5, P = 0.001). CONCLUSIONS: Neutrophils from diabetic animals exhibit higher levels of surface integrin expression and integrin-mediated adhesion. In vivo, CD18 blockade significantly decreases leukostasis in the diabetic retinal microvasculature. Integrin adhesion molecules may serve as therapeutic targets for the treatment and/or prevention of early diabetic retinopathy.

Identificaçäo do(s) receptor(es) da célula hospedeira para a família de glicoproteínas Tc85 presente na superfície do Trypanosoma cruzi / Identification of host cell receptor for TC85 glycoprotein family present in the Trypanosoma cruzi surface

Tripomastigotas, formas infectivas do T. cruzi, expressam em sua superfície uma família de glicoproteínas denominada Tc-85, que pertence à superfamília gênica das gp85/trans-sialidases. Nosso laboratório clonou e caracterizou um membro da família da Tc85 (Tc85-11), cuja região carboxila terminal (clone Tc85-1) adere em laminina e em células de mamíferos. O uso de peptídeos sintéticos, correspondendo em seqüência à Tc85-1 possibilitou a caracterização do motivo mais conservado da superfamília gênica das gp85/trans-sialidases (VTVxNVfLYNR), que não está relacionado a adesão a laminina, como o domínio de adesão em células de mamíferos...

Acquired increase in leucocyte binding by intestinal microvascular endothelium in inflammatory bowel disease.

BACKGROUND: Endothelial cells that line microvascular blood vessels have an important role in inflammation through their ability to bind and recruit circulating leucocytes. Endothelial cells from the intestines of patients with chronically inflamed Crohn's disease and ulcerative colitis--the two forms of inflammatory bowel disease--display an increased leucocyte-binding capacity in vitro. We investigated whether this enhanced leucocyte binding is a primary or an acquired defect. METHODS: We cultured human intestinal microvascular endothelial cells (HIMEC) from the uninvolved intestine and chronically inflamed bowel of three patients with inflammatory bowel disease (two Crohn's disease, one ulcerative colitis). We assessed HIMEC binding to polymorphonuclear leucocytes and U937 cells by means of an adhesion assay. FINDINGS: After activation with interleukin-1beta or lipopolysaccharide, HIMEC from the chronically inflamed tissue in all three patients with inflammatory bowel disease bound twice as many polymorphonuclear leucocytes and U937 cells as endothelial cells from uninvolved tissue. INTERPRETATION: Enhanced leucocyte binding by HIMEC from chronically inflamed tissue in patients with inflammatory bowel disease is an acquired defect since it is not found in the uninvolved intestinal segments from the same individuals. Because interaction between endothelial cells and leucocytes is a key regulatory step in the inflammatory process, this enhanced binding may contribute to the pathophysiology of chronic intestinal inflammation.

Neutrophil migration into the gingival sulcus is associated with transepithelial gradients of interleukin-8 and ICAM-1.

The expression of adhesion molecules and the local production of chemotactic cytokines within the epithelium are considered to be key events in neutrophil (PMN) migration at sites of mucosal infections. In their journey toward the gingival sulcus, PMNs have been shown to selectively migrate through the junctional epithelium. Little, however, is known about the molecular mechanisms involved in this key process aimed at the control of subgingival bacterial plaque. This investigation describes the expression of IL-8 mRNA-positive cells and the establishment of a gradient of intercellular adhesion molecule-1 (ICAM-1) receptors within the junctional epithelium of clinically healthy gingiva. Expression of ICAM-1 and IL-8 was topographically associated with the area of PMN migration; i.e., the junctional epithelium. Levels of ICAM-1 expression increased from the basal cells toward the surface of the junctional epithelium and thus toward areas exposed to bacterial challenges. IL-8 mRNA-positive cells were also present at highest density in the most superficial junctional epithelial layers. The combination of the haptotactic stimuli, resulting from the interaction of the PMN's beta2 integrin receptors with the gradient of ICAM-1 expression, and the location of IL-8 mRNA-positive cells, consistent with the establishment of a discrete PMN chemotactic source, may play an important physiologic role in efficiently routing PMNs to the gingival sulcus. This process contributes to the maintenance of a local host-parasite equilibrium and to the limitation of PMN-associated tissue damage.

Systemic neutrophil intrinsic 5-lipoxygenase activity and CD18 receptor expression linked to reperfusion injury.

OBJECTIVE: To determine if systemic neutrophil intrinsic 5-lipoxygenase (5-LO) inhibition correlates with decreased expression of surface adhesion molecules and attenuation of ischemia-reperfusion (i/r) injury in guinea pig island skin flaps. METHODS: Eighty-one adult female Hartley guinea pigs were divided into one control group, three 2-hour ischemia groups, and four 10-hour ischemia groups. Island dorsal skin flaps were developed (except in the control group), and 2 hours before reperfusion, zileutin (a 5-LO inhibitor) or vehicle was administered orally. Postreperfusion systemic neutrophil receptor expression, neutrophil flap infiltration, and flap survival were measured. Neutrophils from whole blood were analyzed for CD18 containing surface receptor expression using monoclonal antibodies and cell associated fluorescence. Neutrophil infiltration into a distal centimeter squared of flap tissue was assessed using myeloperoxidase antibodies, and flap survival was determined within 7 days postoperatively. RESULTS: Flaps in the treated 2- and 10-hour ischemic groups survived totally intact, while the untreated 10-hour ischemic flaps underwent total necrosis. A significant main effect of the drug was detected using analysis of variance (ANOVA) (P =.0001). Surface receptor detection and neutrophil infiltration were significantly increased in the untreated animals. CONCLUSIONS: Zileuton, a 5-LO inhibitor, reduces adhesion receptor expression on systemic neutrophils and attenuates i/r injury. Systemic neutrophil intrinsic 5-LO activity and CD18 receptor expression are linked to reperfusion injury and may be fundamental events in its pathogenesis.

Effect of hemodialysis on leukocyte adhesion receptor expression.

Hemodialysis with complement-activating membranes such as cuprophane is known to transiently activate leukocytes, leading to increased cellular adhesiveness, pulmonary leukostasis, and reduced functional capacity of monocytes and neutrophils. Clinically, this repetitive cell activation may contribute to the increased morbidity and mortality associated with chronic hemodialysis. To examine the effect of cuprophane hemodialysis on expression of cell-surface proteins involved in leukocyte adhesiveness, we monitored CD11b, CD18, CD14, CD54, and plasma-soluble CD54 in 10 patients during hemodialysis with cuprophan dialyzers. To test the effect of local blood recirculation, in two patients, arterial supply to the dialyzer was accessed from the peripheral arteriovenous fistula and was returned via an indwelling central venous catheter. In an attempt to examine the possible role of membrane-induced complement activation, the results were compared with those seen after incubation with C5a in vitro. Finally, the leukocyte responses to C5a and lipopolysaccharide were measured before and after hemodialysis. Leukocyte expression of CD11b and CD18 increased and CD14 decreased with hemodialysis, while CD54 remained unaltered. Plasma CD54 was markedly elevated before and remained unchanged during hemodialysis. Data obtained with C5a activation in vitro revealed identical changes in CD11b expression as that seen with hemodialysis, suggesting the role of membrane-induced complement activation. Preliminary data obtained using remote arterial and venous access sites showed only a slight increase in CD11b expression in the arterial blood, suggesting that the apparent systemic activation seen with arteriovenous access may be due to recirculation and local activation within the blood access. Finally, dialysis procedure did not impair lipopolysaccharide- or C5a-mediated upregulation of CD11b expression.

Compartmentalized roles for leukocytic adhesion molecules in lung inflammatory injury.

By using the model of acute injury caused by intrapulmonary deposition of IgG immune complexes, blocking mAb to CD11a, CD11b, L-selectin, and intercellular adhesion molecule-1 (ICAM-1) were administered either i.v. or intratracheally (i.t.). The effects of these interventions were assessed according to lung injury, lung content of myeloperoxidase (MPO), TNF-alpha, and cellular content in bronchoalveolar lavage (BAL) fluids, and up-regulation of pulmonary vascular ICAM-1. In animals treated i.v. with Abs to CD11a, L-selectin, or ICAM-1 lung injury was significantly attenuated in parallel with reduced lung content of MPO. Under similar conditions, treatment with anti-CD11b had no effect. However, when the same mAb were administered i.t., anti-CD11a and anti-L-selectin were without protective effects, whereas i.t. administered anti-CD11b and anti-ICAM-1 were each highly protective. The protective effects of anti-CD11b were related to profound reductions in BAL levels of TNF-alpha, pulmonary vascular up-regulation of ICAM-1, and lung content of MPO. The protective effects of i.t.-administered anti-ICAM-1 were not associated with reduced BAL levels of TNF-alpha. Protective effects of mAb were also reflected in reductions of retrievable neutrophils in BAL fluids. mAb to rat CD11b and CD18 but not to rat CD11a suppressed in vitro production of TNF-alpha by immune complex-stimulated rat alveolar macrophages. The mAb did not reduce NO2-/NO3- generation in stimulated macrophages but all mAb (except anti-ICAM-1) reduced O2- responses in macrophages. These data suggest a compartmentalized role for adhesion molecules in lung inflammatory injury after intraalveolar deposition of IgG immune complexes, with CD11a, L-selectin, and ICAM-1 being important in the vascular compartment for neutrophil recruitment, whereas in the alveolar compartment CD11b and ICAM-1 (but not CD11a and L-selectin) seem to play key roles.

Neutrophil adhesion receptor CD18 mediates remote but not localized acid aspiration injury.

BACKGROUND: Acid aspiration leads to lung polymorphonuclear neutrophil (PMN) sequestration and an associated increase in permeability. Although it is known that the neutrophil adhesion receptor (CD18) plays no role in determining PMN accumulations in the region aspirated, we postulated that this PMN adhesion receptor and its endothelial ligand, intercellular adhesion molecule-1 (ICAM-1), mediate remote neutrophil sequestration. METHODS: Anesthetized rabbits underwent localized aspiration of either 0.1N HCl 0.1 ml/kg (n = 18) or saline solution (n = 18). RESULTS: After 30 minutes leukopenia was noted, 2290 +/- 200 white blood cells/mm3 (p < 0.05). At 3 hours diapedesis occurred in the aspirated segment with accumulations in bronchoalveolar lavage fluid (X10(4)) of 87 +/- 6 PMN/ml versus control of 6 +/- 1 PMN/ml (p < 0.05). Histologic evidence of generalized lung leukosequestration occurred. The wet to dry weight ratio of the nonaspirated lung rose to 5.7 +/- 0.2 versus control of 3.9 +/- 0.1 (p < 0.05). Treatment (n = 18) with the CD18 monoclonal antibody (mAb) (R15.7, 1 mg/kg) had no effect on neutrophil accumulations in the aspirated segment. However, the mAb attenuated the remote inflammatory response: early leukopenia (5790 +/- 400 white blood cells/mm3); lung leukosequestration (24 +/- 4 PMN/10 high-power fields); protein leak in bronchoalveolar lavage fluid (570 +/- 50 micrograms/ml); and edema, wet to dry weight ratio (4.9 +/- 0.1) (all p < 0.05). Treatment with the ICAM-1 mAb (RR1/1, 1 mg/kg) (n = 9) did not reduce neutrophil accumulations in the aspirated segment but limited the remote inflammatory response. CONCLUSIONS: Acid aspiration leads to neutrophil adhesion and edema in regions remote from those aspirated via neutrophil CD18 and endothelial ICAM-1.

Salivary up-regulation of human polymorphonuclear leucocyte chemotaxis and adhesion-molecule expression.

Chemotaxis and adhesion molecules were investigated in peripheral blood neutrophils incubated with saliva collected from healthy donors. A salivary concentration of 20% increased chemotactic responses and CD11a/CD18 and CD11b/CD18 expression, but had no effect on formyl-methionyl-leucyl-phenylalanine receptors.

Modulation of host response to Escherichia coli o157:H7 infection by anti-CD18 antibody in rabbits.

BACKGROUND/AIMS: Escherichia coli O157:H7 infection induces diarrhea, severe colitis, and colonic electrolyte transport abnormalities characterized by decreased Na absorption and Cl secretion. The aim of this study was to examine the role of the host inflammatory response in inducing distal colonic transport changes during infection with E. coli O157:H7. METHODS: New Zealand white rabbits aged 10 days were infected with E. coli O157:H7 strain EDL933 (plasmid+, verotoxin 1+, verotoxin 2+). Studies were performed daily from day 1 to day 5 postinfection and compared with uninfected controls (10 days old). Distal colonic ion transport was studied in vitro under short-circuited conditions in Ussing chambers, and tissue inflammation was assessed by mucosal myeloperoxidase activities and mucosal neutrophil (polymorphonuclear neutrophil [PMN]) counts. In a second study, PMN infiltration was inhibited by an anti-CD18 (leukocyte adhesion molecule) monoclonal antibody, IB4, and histology and transport were studied on day 5 postinfection. RESULTS: Infection with O157:H7 induced diarrhea and inhibition of Na absorption by day 3. CI secretion occurred on day 5, coincident with tissue infiltration with PMN. Pretreatment with IB4 prevented histological damage and tissue infiltration with PMN, and it inhibited the transport abnormalities induced by infection alone. CONCLUSIONS: Infection with O157:H7 reduces Na absorption and stimulates Cl secretion in the distal colon. Disruption of the epithelium and changes in colonic electrolyte transport during enterohemorrhagic E. coli are mediated by the host inflammatory response.

CD11b/CD18 expression, adherence, and chemotaxis of granulocyte in adult respiratory distress syndrome.

The accumulation of granulocytes in the pulmonary microvasculature is generally thought a cardinal event in the pathology of adult respiratory distress syndrome (ARDS). However, the mechanism by which granulocytes are sequestered in the pulmonary vascular bed remains largely unknown. Because the CD11b/CD18 membrane receptors mediate various adhesion-dependent functions, their expression was investigated in granulocytes from patients during the course of ARDS development in relation to adherence and chemotaxis. CD11b expression of ARDS resting granulocytes was increased within 24 h of ARDS onset by a factor of two in comparison with control patients (p < 0.05) and remained significantly increased 72 to 120 h later. In contrast, the stimulated expression was significantly decreased only within 24 h of ARDS onset. Adherence was not modified within 8 h of the onset of ARDS, but was increased at Days 1, 3, and 5. The time course of granulocyte chemotaxis shows a decreased chemotaxis capacity during the first 3 d of ARDS, followed by normalization at Day 5. The dynamic changes observed in the various functions studied indicate a possible relationship between the modulation of the CD11b expression and a hyperadhesive state of granulocytes in ARDS. These sticky granulocytes may potentially contribute to the microvascular injury.