The role of leukocyte adhesion molecules in acute transplant rejection

The specific adhesion of cells to other cells or to particular tissues or tissue components is a basic function of cell migration and recognition and underlies many biologic processes including embryogenesis, repair, and immunity. Adhesion molecules are involved in and mediate most cell to cell interactions, implement migration of leukocytes to inflammatory or alloantigenic sites, and costimulate well activation and transformation. Because of these functions, the subject of adhesion molecules is gaining broader interest in the field of transplantation, particularly in the conceptualization and development of future treatment strategies. These molecules influence not only the first interaction between host leukocytes and vascular endothelial cells of the graft but also their migration through the grafted tissues. These contacts seem to be based initially on antigen-independent events of adhesion, which then progress to the antigen-dependent events of antigen recognition and host cell activation. This review evaluates current studies concerning the role of adhesion molecules in the context of the multifaceted processes of allograft rejection.     

L-selectin crosslinking induces integrin-dependent adhesion: evidence for a signaling pathway involving PTK but not PKC

L-selectin mediates the initial contact of leukocytes with the endothelium prior to extravasation. Here we demonstrate that L-selectin engagement can induce rapid and avid integrin-dependent T cell adhesion to recombinant immobilized cell adhesion molecules (CAMs) including ICAM-1, ICAM-3, and VCAM-1, as well as to the extracellular matrix protein fibronectin (FN). L-selectin-induced adhesion to these integrin ligands shares characteristics with CD3 mAb- or phorbol ester-induced adhesion in requiring metabolic energy, tyrosine kinase and ligand-stimulated Ca2+ channel activity. However, L-selectin-induced adhesion is distinct from that induced by phorbol ester or CD3 crosslinking in being relatively independent of protein kinase C (PKC) activity and actin polymerization. Consistent with the higher levels of L-selectin expression on CD45RA+ (naive) cells, L-selectin crosslinking induces a greater proportion of naive relative to memory cell binding to CAMs and FN. In contrast, exposure to phorbol ester or CD3 crosslinking is more effective in inducing CD45RO+ (memory) cell adhesion. Thus, in addition to its role in leukocyte capture and rolling on the endothelium, L-selectin may contribute to beta 1 and beta 2 integrin-dependent binding and arrest.     

The cytoplasmic domains of E- and P-selectin do not constitutively interact with alpha-actinin and are not essential for leukocyte adhesion

The selectins are a family of carbohydrate-binding adhesion molecules involved in the regulation of leukocyte migration. Although there is strong homology between different selectins in their extracellular regions, there is none in the cytoplasmic tails, suggesting selectin-specific functions for these domains. Our previous work showed that the cytoplasmic tail of L-selectin interacts with the actin cytoskeleton via alpha-actinin and vinculin, and that truncation of the cytoplasmic tail of L-selectin blocked both association with alpha-actinin and vinculin and leukocyte adhesion. In the present study, the effects of truncation of the cytoplasmic tails of E- or P-selectin on cell adhesion and cell surface expression were examined, and possible interactions between alpha-actinin and the E- and P-selectin cytoplasmic tails were assessed. In contrast to previous observations demonstrating a requirement for the L-selectin cytoplasmic tail, truncation of the E- or P-selectin cytoplasmic domains had no effect on cell adhesion, or on cell surface expression, when assessed in transiently transfected COS cells. This lack of effect on cell surface expression and adhesion was also observed when transfections were performed with lower amounts of cDNA, which led to submaximal levels of expression. In addition, no interaction between alpha-actinin and the cytoplasmic tails of either E- or P-selectin could be detected under conditions in which binding of alpha-actinin to the L-selectin cytoplasmic tail could be readily demonstrated. Therefore, interactions between the cytoplasmic tail of E- or P-selectin and alpha-actinin or other cytoskeletal proteins are not necessary for leukocyte adhesion per se, but may facilitate downstream biologic events.     

Soluble adhesion molecules correlate with liver inflammation and fibrosis in chronic hepatitis C treated with interferon-alpha

Investigators have recently identified a two-factor structure underlying posttraumatic stress symptoms through the use of exploratory factor analysis. [Taylor et al. (1988). The structure of posttraumatic stress symptoms. Journal of Abnormal Psychology, 107, 154-160]. These two factors, which were labeled as Intrusion and Avoidance, and Hyperarousal and Numbing, are consistent with current theoretical models of posttraumatic stress disorder--PTSD [e.g. Foa et al. (1992). Uncontrollability and unpredictability in post-traumatic stress disorder: An animal model. Psychological Bulletin, 112, 218-238]. However, the authors of the Taylor et al. study issued caution in interpreting their findings because there has yet to be a systematic replication of their results. This paper presents a confirmatory factor analysis of the two-factor structure of posttraumatic stress symptoms in 217 survivors of serious motor vehicle accidents with varying degrees of PTSD symptoms. A hierarchical, confirmatory-factor analysis conducted with a structural equation modeling statistics package confirmed that the model proposed by Taylor et al. can adequately account for the presentation of PTSD symptoms in this sample of motor vehicle accident survivors. The implications for the assessment and diagnosis of PTSD are discussed.     

The effect of leukotriene synthesis inhibitors in models of acute and chronic inflammation

To define the risk factors related to the occurrence of fungemia in children infected with human immunodeficiency virus (HIV), we performed a matched case-control study. During a 6-year period (1987-1993), fungemia developed in 22 (6.3%) of 347 HIV-infected children observed at the Pediatric Branch of the National Cancer Institute. Each of these 22 cases was matched by age and gender with three controls. Multiple logistic regression indicated that the best predictor of fungemia in this population was the presence of a central venous catheter placed for > 90 days (P < .00001), followed by a group of risk factors composed of 10 independent variables adjusted for a CD4 cell count of < 100/MicroL (P < .045). Those variables included treatment with more than three antibiotics, treatment with more than three parenteral antibiotics, > 30 days of antibiotic treatment, bacterial infections, > 30 days in the hospital, hypoalbuminemia, C3 (Centers for Disease Control and Prevention) classification of HIV infection, and malnourishment. We conclude that prolonged placement of central venous catheters is the most important risk factors for fungemia in HIV-infected children and that the risk of fungemia is further influenced by antibacterial therapy, catheter manipulation, and host response.     

The role of adhesion molecules in human leukocyte attachment to porcine vascular endothelium: implications for xenotransplantation

Many obstacles still prevent successful xenotransplantation of porcine donor organs. When hyperacute rejection is averted, transplanted pig organs are subject to acute vascular and cellular rejection. In autologous systems, leukocyte recruitment into inflamed tissues involves selectins, integrins, and Ig family members. To determine whether these mechanisms allow human leukocytes to effectively enter porcine grafts, the pathways by which human leukocytes adhere to TNF-alpha-stimulated porcine aortic endothelium were examined under static and physiologic flow conditions. L-selectin and E-selectin had overlapping functions in neutrophil capture and rolling, whereas Ab blockade of E-selectin and the beta2 integrins inhibited firm arrest of rolling neutrophils. Combined blockade of selectins and beta2 integrins resulted in negligible human neutrophil attachment to pig endothelium. Lymphocyte attachment to porcine endothelium was primarily L-selectin mediated, whereas beta2 integrin and VCAM-1/very late Ag-4 (VLA-4) interactions promoted static adhesion. Concurrent beta2 integrin, VLA-4, VCAM-1, and L-selectin blockade completely inhibited lymphocyte attachment. Thus, interactions between leukocyte-endothelial cell adhesion receptor pairs remained remarkably intact across the human-porcine species barrier. Moreover, disrupting the adhesion cascade may impair the ability of human leukocytes to infiltrate a transplanted porcine organ during rejection.     

The roles of adhesion molecules, cytokines and chemokines in allergic inflammation

Recently, adhesion molecules, as well as eosinophils, have been found to play an important role in the inflammatory processes in allergic disease. We demonstrated here as below. Characteristics of adhesion molecules expression on eosinophils in asthma, namely, high-intensity expression of adhesion molecules. Induction of adhesion molecule expression by PAF and RANTES and in addition induction by the supernatant of mononuclear cells from mite-allergic asthmatic patients stimulated with mite-allergen as well as with a combination of the recombinant IL-3, GM-CSF and IL-5. Elevated soluble ICAM-1 in bronchial asthma. Moreover, the presence of a large variety of membrane receptors and the identification of cytotoxic molecules (mainly granule basic proteins) have indicated that eosinophils should be considered as effector cells. We therefore investigated the possible release of granule proteins in response to signaling from ICAM-1 and its ligands. The concentrations of eosinophil cationic protein and eosinophil-derived neurotoxin in supernatants of eosinophils were significantly greater (p < 0.05) in the presence of recombinant soluble ICAM-1 than without it. These results suggest that signaling from ICAM-1 and its ligands might induce eosinophil activation and might be involved in degranulation of eosinophil granule proteins. In addition, reactive oxygen species generated by eosinophils have also been considered capable of causing airway injury at the inflamed focus. We examined the effect of recombinant soluble ICAM-1 and its ligands on eosinophil-induced radical oxygen products. Recombinant soluble ICAM-1 augmented eosinophil oxidative metabolism. It was concluded that signaling via adhesion molecules might play an important role in the pathogenesis of allergic inflammation through activation of eosinophils, such as through an increase in oxidative metabolism or degranulation of eosinophil granule proteins.     

The roles of L-selectin, beta 7 integrins, and P-selectin in leukocyte rolling and adhesion in high endothelial venules of Peyer's patches

Lymphocyte trafficking into Peyer's patches requires beta 7 integrins and L-selectin. Here, we use intravital microscopy to examine leukocyte rolling and adhesion in Peyer's patch high endothelial venules (HEV) of wild-type, L-selectin-deficient (L-/-), beta 7 integrin-deficient (beta 7-/-), and beta 7/L(-/-) mice. Although the leukocyte rolling flux fraction was reduced by 70%, Peyer's patches in L-/- mice were of normal size and cellularity. In beta 7-/- mice, the rolling flux fraction was normal, but the number of adherent leukocytes in HEV was greatly reduced. The median leukocyte rolling velocity was reduced in L-/- mice and increased in beta 7-/- mice, suggesting that beta 7 integrins and L-selectin mediate rolling in Peyer's patch HEV at different velocities. beta 7/L(-/-) exhibited both a low rolling flux fraction and low adhesion and had severely reduced Peyer's patch size and cellularity. The residual rolling in these mice was completely blocked by a P-selectin mAb. A significant P-selectin component was also detected in the other genotypes. Twenty-six percent of B and T lymphocytes isolated from Peyer's patches of wild-type mice expressed functional ligands for P-selectin, and this fraction was increased to 57% in beta 7/L(-/-) mice. Peyer's patch HEV were found to express P-selectin under the conditions of intravital microscopy, but not in situ. Our data suggest a novel P-selectin dependent mechanism of lymphocyte homing to Peyer's patches. In situ, beta 7 integrins and L-selectin account for all lymphocyte homing to Peyer's patches, but P-selectin-dependent rolling, as induced by minimal trauma, may support trafficking of effector T lymphocytes to Peyer's patches.     

Serum levels of soluble adhesion molecules in chronic renal failure and dialysis patients

The N-type voltage-operated calcium channel has been characterized over the years as a high-threshold channel, with variable inactivation kinetics, and a unique ability to bind with high affinity and specificity omega-conotoxin GVIA and related toxins. This channel is particularly expressed in some neurons and endocrine cells, where it participates in several calcium-dependent processes, including secretion. Omega-conotoxin GVIA was instrumental not only for the biophysical and pharmacological characterization of N-type channels but also for the development of in vitro assays for studying N-type VOCC subcellular localization, biosynthesis, turnover, as well as short-and long-term regulation of its expression. We here summarize our studies on N-type VOCC expression in neurosecretory cells, with a major emphasis on recent data demonstrating the presence of N-type channels in intracellular secretory organelles and their recruitment to the cell surface during regulated exocytosis.     

Expression of cell adhesion molecules and common acute lymphoblastic leukaemia antigen in hepatoblastoma

Hepatoblastoma is an embryonal tumour of the liver, which often contains tissue components with multidirectional differentiation. The occurrence of cell surface antigens in this tumour has not been studied systematically, and we therefore investigated 20 hepatoblastomas for the expression of common acute lymphoblastic leukaemia antigen (CALLA) and cell adhesion molecules (CAMs) in their different tissue components. Epithelial tumour cells of fetal differentiation contained E-cadherin. This protein did not occur in tumour areas with embryonal or mesenchymal differentiation. In contrast, immature embryonal and anaplastic cells expressed CALLA and the hyaluronate receptor (HCAM, CD44). Both fetal and embryonal areas stained irregularly positive for ICAM-1, which, in contrast, was not present on anaplastic cells. Immature fibrous tissue did not contain any of these molecules except for ICAM-1. However, some cells adjacent to, or enclosed in, osteoid were positive for HCAM and NCAM. Like small undifferentiated hepatoblastoma cells, primitive mesenchymal spindle-shaped cells also expressed CALLA, HCAM, and the polysialylated embryonic form of NCAM strongly. This last is not present on other epithelial or mesenchymal tumour cells. Hepatoblastoma cells of varying differentiation express distinct patterns of CAMs and CALLA. Our results give further insight into their histogenesis and cellular interactions and may explain their variable ability for invasive growth and formation of metastases.     

Cytokine mediators in acute inflammation and chronic course of viral hepatitis

We examine the cognitive ability of 58 demented patients who were evaluated with the Spanish version of the Severe Impairment Battery (SIB). The SIB is composed of multiple simple subtests for memory, language, orientation, attention, visual perception and ability to construct. The battery also assesses social skills, praxis and the ability to respond appropriately to name. The mean SIB scores (72.55 +/- 17.99; range 8-99) correlated with mean scores (10.76 +/- 6.41; range 0-31) on the Spanish version of Folstein's Mini-Mental State Examination (MMSE). The SIB detected deterioration in the nine cognitive areas examined, even in the most severely impaired patients (MMSE = 0-6). These results indicate that the Spanish version of the SIB is a useful instrument for examining severely demented patients.     

IL-10 regulates liver pathology in acute murine Schistosomiasis mansoni but is not required for immune down-modulation of chronic disease

We have used IL-10 gene knockout mice (IL-10T) to examine the role of endogenous IL-10 in the down-modulation of hepatic granuloma formation and lymphocyte responses that occurs in chronic infection with the helminth parasite Schistosoma mansoni. Although IL-10-deficient animals showed 20 to 30% mortality between 8 and 14 wk postinfection, they displayed no alterations in their susceptibility to infection and produced similar numbers of eggs as their wild-type littermates. The IL-10T mice displayed a significant increase in hepatic granuloma size at the acute stage of infection, which was associated with increased IFN-gamma, IL-2, IL-1beta, and TNF-alpha mRNA expression in liver and elevated Th1-type cytokine production by lymphoid cells. Despite developing an enhanced Th1-type cytokine response, the IL-10T mice showed no consistent decrease in their Th2-type cytokine profile. Surprisingly, although granulomatous inflammation was enhanced at the acute stage of infection, the livers of IL-10T mice displayed no significant increase in fibrosis and underwent normal immune down-modulation at the chronic stage of infection. Moreover, the down-modulated state could be induced in IL-10T mice by sensitizing the animals to schistosome eggs before infection, further demonstrating that the major down-regulatory mechanism is not dependent upon IL-10. We conclude that while IL-10 plays an important role in controlling acute granulomatous inflammation, it plays no essential role in the process of immune down-modulation in chronic schistosome infection.     

Semantic effects in naming perceptual identification but not in delayed naming: Implications for models and tasks.

Previous research has demonstrated that the subjective danger and usefulness of words affect lexical decision times. Usually, an interaction is found: Increasing danger predicts faster reaction times (RTs) for words low on usefulness, but increasing danger predicts slower RTs for words high on usefulness. The authors show the same interaction with immediate auditory naming. The interaction disappeared with a delayed auditory naming control experiment, suggesting that it has a perceptual basis. In an attempt to separate input (signal to ear) from output (brain to muscle) processes in word recognition, the authors ran 2 auditory perceptual identification experiments. The interaction was again significant, but performance was best for words high on both danger and usefulness. This suggests that initial demonstrations of the interaction were reflecting an output approach/withdraw response conflict induced by stimuli that are both dangerous and useful. The interaction cannot be characterized as a tradeoff of speed versus accuracy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alteration of Hepatic microsomal enzyme systems and the lethal action of non-steroidal anti-arthritic drugs in acute and chronic models of inflammation

Depression of the hepatic microsomal enzyme system(s) in adjuvant-induced polyarthritis (AIP), a chronic inflammation model, has been confirmed indirectly by the enhancement of hexobarbital Na-induced sleeping time and extended for the first time to zoxazolamine-induced paralysis. In addition, barbital Na-induced anesthesia was increased during the course of AIP development, indicating that the CNS of these rats appears to be more sensitive to drug effects, since this barbiturate is excreted virtually unmetabolized. Most likely because of these effects, LD50 values for acetylsalicylic acid, phenylbutazone and indomethacin in AIP rats decreased in terms of mg/kg (increased toxicity) as the disease became more severe (Day 21) since they are known ultimately to be metabolized by the liver. On the other hand, the toxicity of a new non-steroidal anti-inflammatory agent, meseclazone, was not altered significantly in AIP. This is most likely due to the fact that its near total conversion to 5-chlorosalicylic acid has been shown to occur by hydrolytic cleavage as it pases through the intestinal wall with litter hepatic involvement. Finally, carrageenan edema, a model of acute inflammation, did not affect barbiturate sleeping times of zoxazolamine paralysis, nor were any of these drugs studied more lethal in this disease state.     

Pharmacodynamics and pharmacokinetics of tolfenamic acid in ruminating calves: evaluation in models of acute inflammation

Injections of mild irritants intradermally (carrageenan, zymosan and dextran) and intracaveally (carrageenan) in a tissue cage model of inflammation were used in studies of the pharmacodynamics and pharmacokinetics of tolfenamic acid administered intramuscularly in calves. Inhibition of serum thromboxane (TX)B2 and inflammatory exudate prostaglandin (PG)E2 were used as indicators of the magnitude and time course of blockade of cyclo-oxygenase isoforms COX-1 and COX-2, respectively. Single doses of 2, 4 and 8 mgkg-1 tolfenamic acid partially inhibited irritant-induced rises in skin temperature (non-dose dependently) and skin oedema (dose-dependently). These doses also markedly inhibited serum TXB2 synthesis and the duration of inhibition was dose-related. A dose of 2 mgkg-1 tolfenamic acid also attenuated skin temperature rise over carrageenan-injected tissue cages, and markedly inhibited exudate PGE2 synthesis, even though drug penetration into both exudate and tissue cage transudate was limited. Tolfenamic acid pharmacokinetics were characterized by a relatively short tmax (0.94-2.04 h), a high estimated Vdarea (1.79-3.20 Lkg-1), an estimated t1/2 beta of 8.01-13.50 h and Cl beta of 0.142-0.175 Lkg-1h-1. The actions of tolfenamic acid in inhibiting PGE2 synthesis and in attenuating two of the cardinal signs of inflammation (heat and swelling) suggest that a dosage of 2 mgkg-1 administered intramuscularly should be effective clinically as an anti-inflammatory agent.     

Emotional scenes in peripheral vision: Selective orienting and gist processing, but not content identification.

Emotional-neutral pairs of visual scenes were presented peripherally (with their inner edges 5.2° away from fixation) as primes for 150 to 900 ms, followed by a centrally presented recognition probe scene, which was either identical in specific content to one of the primes or related in general content and affective valence. Results indicated that (a) if no foveal fixations on the primes were allowed, the false alarm rate for emotional probes was increased; (b) hit rate and sensitivity (A') were higher for emotional than for neutral probes only when a fixation was possible on only one prime; and (c) emotional scenes were more likely to attract the first fixation than neutral scenes. It is concluded that the specific content of emotional or neutral scenes is not processed in peripheral vision. Nevertheless, a coarse impression of emotional scenes may be extracted, which then leads to selective attentional orienting or--in the absence of overt attention--causes false alarms for related probes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lymphotoxin alpha3 induces chemokines and adhesion molecules: insight into the role of LT alpha in inflammation and lymphoid organ development

Lymphotoxin (LT) plays an important role in inflammation and lymphoid organ development, though the mechanisms by which it promotes these processes are poorly understood. Toward this end, the biologic activities of a recently generated recombinant murine (m) LT alpha preparation were evaluated. This cytokine preparation was effective at inducing cytotoxicity of WEHI target cells with 50% maximal killing observed with 1.2 ng/ml. mLT alpha also induced the expression of inflammatory mediators in the murine endothelial cell line bEnd.3. rmLT alpha induced expression of the adhesion molecules VCAM, ICAM, E-selectin, and the mucosal addressin cellular adhesion molecule, MAdCAM-1. When mLT alpha, human (h) LT alpha, and mTNF-alpha were compared, mLT alpha was the most potent inducer of MAdCAM-1. None of these cytokines induced the peripheral node addressin, PNAd. mLT alpha also induced expression of the chemokines RANTES, IFN-inducible protein 10 (IP-10), and monocyte chemotactic protein 1 (MCP-1). mRNA levels peaked 4 h following treatment with mLT alpha and declined through the 24-h treatment period. LT alpha also induced chemokine protein within 8 h of treatment, which increased through the 24-h treatment period. These data demonstrate that the proinflammatory effects of LT alpha3 may be mediated in part through the induction of adhesion molecule and chemokine expression. Further, LT alpha3 may promote development of lymphoid tissue through induction of chemokines and the mucosal addressin MAdCAM-1. These data confirm previous observations in transgenic and knockout mice that LT alpha3 in the absence of LT beta carries out unique biologic activities.     

Structural requirements for outside-in and inside-out signaling by Drosophila neuroglian, a member of the L1 family of cell adhesion molecules

Expression of the Drosophila cell adhesion molecule neuroglian in S2 cells leads to cell aggregation and the intracellular recruitment of ankyrin to cell contact sites. We localized the region of neuroglian that interacts with ankyrin and investigated the mechanism that limits this interaction to cell contact sites. Yeast two-hybrid analysis and expression of neuroglian deletion constructs in S2 cells identified a conserved 36-amino acid sequence that is required for ankyrin binding. Mutation of a conserved tyrosine residue within this region reduced ankyrin binding and extracellular adhesion. However, residual recruitment of ankyrin by this mutant neuroglian molecule was still limited to cell contacts, indicating that the lack of ankyrin binding at noncontact sites is not caused by tyrosine phosphorylation. A chimeric molecule, in which the extracellular domain of neuroglian was replaced with the corresponding domain from the adhesion molecule fasciclin II, also selectively recruited ankyrin to cell contacts. Thus, outside-in signaling by neuroglian in S2 cells depends on extracellular adhesion, but does not depend on any unique property of its extracellular domain. We propose that the recruitment of ankyrin to cell contact sites depends on a physical rearrangement of neuroglian in response to cell adhesion, and that ankyrin binding plays a reciprocal role in stabilizing the adhesive interaction.