Lung injury after deposition of IgA immune complexes. Requirements for CD18 and L-arginine

Acute lung injury produced by deposition of IgA immune complexes is complement-dependent, neutrophil-independent, oxygen radical-mediated, and may be a result of the formation of the hydroxyl radical (HO) generated directly or indirectly from activated lung macrophages. The current studies were designed to evaluate further the pathophysiologic events that occur after intrapulmonary deposition of IgA immune complexes. Pretreatment of rats with the human recombinant soluble complement receptor-1 resulted in marked attenuation of IgA immune complex-induced lung injury. Intravenous administration of antibody to CD18, but not antibody to CD11b, was highly protective against lung injury. Treatment of animals with either anti-endothelial leukocyte-adhesion molecule-1 or anti-TNF-alpha, both of which were highly protective against IgG immune complex-induced lung injury, had no protective effects in the model of IgA immune complex-induced lung injury. Immunohistochemical analysis revealed up-regulation of the endothelial leukocyte adhesion molecule-1 in the pulmonary vasculature after deposition of IgA immune complexes. This up-regulation was TNF-alpha-dependent. The arginine analog, NG-monomethyl-L-arginine, was highly protective against IgA immune complex-induced lung injury. This protective effect was reversed by the co-presence of L-arginine (but not D-arginine). Protective interventions against IgA immune complex-induced lung injury were inversely correlated with the numbers of macrophages that could be retrieved by lung lavage. These data suggest fundamental differences in the pathogenesis of lung injury after intrapulmonary deposition of IgA immune complexes, as compared with injury caused by deposition of IgG immune complexes. In the latter, neutrophils, intrapulmonary generation of TNF-alpha, and up-regulation of pulmonary vascular endothelial leukocyte-adhesion molecule-1 are required for the full development of lung injury, whereas no such requirements appear in the case of IgA immune complex-induced lung injury. Full expression of IgA immune complex-induced lung injury also appears to require L-arginine, suggesting a possible role for nitric oxide or its derivatives in events ultimately leading to injury.

Lung injury after deposition of IgA immune complexes. Requirements for CD18 and L-arginine

Acute lung injury produced by deposition of IgA immune complexes is complement-dependent, neutrophil-independent, oxygen radical-mediated, and may be a result of the formation of the hydroxyl radical (HO) generated directly or indirectly from activated lung macrophages. The current studies were designed to evaluate further the pathophysiologic events that occur after intrapulmonary deposition of IgA immune complexes. Pretreatment of rats with the human recombinant soluble complement receptor-1 resulted in marked attenuation of IgA immune complex-induced lung injury. Intravenous administration of antibody to CD18, but not antibody to CD11b, was highly protective against lung injury. Treatment of animals with either anti-endothelial leukocyte-adhesion molecule-1 or anti-TNF-alpha, both of which were highly protective against IgG immune complex-induced lung injury, had no protective effects in the model of IgA immune complex-induced lung injury. Immunohistochemical analysis revealed up-regulation of the endothelial leukocyte adhesion molecule-1 in the pulmonary vasculature after deposition of IgA immune complexes. This up-regulation was TNF-alpha-dependent. The arginine analog, NG-monomethyl-L-arginine, was highly protective against IgA immune complex-induced lung injury. This protective effect was reversed by the co-presence of L-arginine (but not D-arginine). Protective interventions against IgA immune complex-induced lung injury were inversely correlated with the numbers of macrophages that could be retrieved by lung lavage. These data suggest fundamental differences in the pathogenesis of lung injury after intrapulmonary deposition of IgA immune complexes, as compared with injury caused by deposition of IgG immune complexes. In the latter, neutrophils, intrapulmonary generation of TNF-alpha, and up-regulation of pulmonary vascular endothelial leukocyte-adhesion molecule-1 are required for the full development of lung injury, whereas no such requirements appear in the case of IgA immune complex-induced lung injury. Full expression of IgA immune complex-induced lung injury also appears to require L-arginine, suggesting a possible role for nitric oxide or its derivatives in events ultimately leading to injury.

Neutrophil adherence to isolated adult cardiac myocytes. Induction by cardiac lymph collected during ischemia and reperfusion

Canine neutrophils can be induced to adhere in vitro to isolated adult cardiac myocytes by stimulation of the neutrophils with chemotactic factors such as zymosan-activated serum (ZAS) only if the myocytes have been previously exposed to cytokines such as interleukin 1 (IL-1) or tumor necrosis factor-alpha. These cytokines induce synthesis and surface expression of intercellular adhesion molecule-1 (ICAM-1) on the myocyte, and neutrophil adhesion is almost entirely CD18 and ICAM-1 dependent. The present study examines cardiac-specific lymph collected from awake dogs during 1-h coronary occlusion and 3 d of reperfusion for its ability to induce both ICAM-1 expression in cardiac myocytes, and neutrophil-myocyte adherence. Reperfusion lymph induced ICAM-1 expression in isolated myocytes, and myocyte adherence to ZAS-stimulated neutrophils that was completely inhibited by anti-CD18 and anti-ICAM-1 monoclonal antibodies. This activity peaked at 90 min of reperfusion and persisted for up to 72 h. Preischemic lymph was not stimulatory. IL-1 appeared not to be a stimulating factor in lymph in that dilutions of lymph were found to inhibit the stimulatory effects of recombinant IL-1 beta. However, investigation of interleukin 6 (IL-6) revealed that recombinant IL-6 stimulated myocyte adhesiveness for ZAS-stimulated neutrophils (ED50 = 0.002 U/ml) and expression of ICAM-1 by isolated myocytes. IL-6 neutralizing antibody markedly reduced the ability of reperfusion lymph to stimulate adhesion and ICAM-1 expression, and estimates of levels of IL-6 in reperfusion lymph ranged from 0.035 to 0.14 U/ml. These results indicate that cytokines capable of promoting neutrophil-myocyte adhesion occur in extracellular fluid during reperfusion of ischemic myocardium, and that one of these cytokines is IL-6. Neutrophil-myocyte adhesion may be of pathogenic significance because it may enhance the cytotoxic activity of the neutrophil.

Roles of beta 2 integrins of rat neutrophils in complement- and oxygen radical-mediated acute inflammatory injury

The roles of beta 2 integrin molecules in neutrophil accumulation and tissue injury have been examined by the use of antibodies that are reactive with human CD11b and CD18 and cross-react with the homologous epitopes on rat neutrophils. Adherence to rat pulmonary artery endothelial cells by human neutrophils and endothelial cell killing by phorbol ester-activated human neutrophils required CD11b, CD11c, and CD18. Companion adherence studies between rat neutrophils and endothelial cells revealed a requirement for both CD11b and CD18. Neither anti-CD11b nor anti-CD18 depressed in vitro responses (O2- generation and chemotactic migration) of rat neutrophils. The accumulation of neutrophils in glycogen-induced peritoneal exudates was diminished substantially in rats treated with either anti-CD18 or anti-CD11b. In oxidant-mediated acute lung injury induced by rapid intravascular infusion of cobra venom factor, treatment of rats with either anti-CD18 or anti-CD11b significantly attenuated injury as assessed by increases in vascular permeability and hemorrhage. These protective effects correlated morphologically with diminished adhesion of neutrophils to interstitial intrapulmonary capillary endothelial cells. In studies of immune complex (BSA-anti-BSA)-induced alveolitis and dermal vasculitis, anti-CD18 had protective effects at all doses of anti-BSA employed. The protective effects of anti-CD18 correlated with diminished neutrophil accumulation in tissues at lower doses of anti-BSA. Although anti-CD11b was not effective under the same experimental conditions, intratracheal administration of this antibody conveyed protection against immune complex-induced lung injury, suggesting that both CD11b and CD18 are required for the full expression of injury. The current studies also demonstrated that when surface-bound IgG immune complexes were treated with fresh rat serum, the increment in O2- and TNF alpha generated by alveolar macrophages was suppressed by anti-CD18, but not by anti-CD11b, suggesting a heretofore unrecognized role for CD18 in the O2- and TNF-alpha responses of alveolar macrophages. Thus, neutrophil beta 2 integrins play a requisite role for the full expression of complement-dependent and oxygen radical-mediated injury of the lung and dermal vasculature.

Roles of beta 2 integrins of rat neutrophils in complement- and oxygen radical-mediated acute inflammatory injury

The roles of beta 2 integrin molecules in neutrophil accumulation and tissue injury have been examined by the use of antibodies that are reactive with human CD11b and CD18 and cross-react with the homologous epitopes on rat neutrophils. Adherence to rat pulmonary artery endothelial cells by human neutrophils and endothelial cell killing by phorbol ester-activated human neutrophils required CD11b, CD11c, and CD18. Companion adherence studies between rat neutrophils and endothelial cells revealed a requirement for both CD11b and CD18. Neither anti-CD11b nor anti-CD18 depressed in vitro responses (O2- generation and chemotactic migration) of rat neutrophils. The accumulation of neutrophils in glycogen-induced peritoneal exudates was diminished substantially in rats treated with either anti-CD18 or anti-CD11b. In oxidant-mediated acute lung injury induced by rapid intravascular infusion of cobra venom factor, treatment of rats with either anti-CD18 or anti-CD11b significantly attenuated injury as assessed by increases in vascular permeability and hemorrhage. These protective effects correlated morphologically with diminished adhesion of neutrophils to interstitial intrapulmonary capillary endothelial cells. In studies of immune complex (BSA-anti-BSA)-induced alveolitis and dermal vasculitis, anti-CD18 had protective effects at all doses of anti-BSA employed. The protective effects of anti-CD18 correlated with diminished neutrophil accumulation in tissues at lower doses of anti-BSA. Although anti-CD11b was not effective under the same experimental conditions, intratracheal administration of this antibody conveyed protection against immune complex-induced lung injury, suggesting that both CD11b and CD18 are required for the full expression of injury. The current studies also demonstrated that when surface-bound IgG immune complexes were treated with fresh rat serum, the increment in O2- and TNF alpha generated by alveolar macrophages was suppressed by anti-CD18, but not by anti-CD11b, suggesting a heretofore unrecognized role for CD18 in the O2- and TNF-alpha responses of alveolar macrophages. Thus, neutrophil beta 2 integrins play a requisite role for the full expression of complement-dependent and oxygen radical-mediated injury of the lung and dermal vasculature.

Insoluble immune complex-stimulated neutrophil leukotriene B4 production is dependent on Fc gamma RII and Fc gamma RIII and independent of pertussis toxin-sensitive signal transduction pathways

Leukotriene B4 (LTB4) release initiated by interaction of immune complexes (ICs) with Fc gamma RII and Fc gamma RIII receptors on human neutrophils was studied using well-defined complexes. Immune complexes consisting of polyclonal rabbit antibody to human albumin were prepared at equivalence (insoluble complex) and at five times antigen excess (soluble complex). Incubation of human neutrophils with soluble and insoluble ICs led to the synthesis of LTB4 from endogenous arachidonic acid (AA). LTB4 release induced by ICs was markedly inhibited by monoclonal antibodies against either Fc gamma RII or Fc gamma RIII receptor. Treatment of neutrophils with pertussis toxin significantly inhibited the release of LTB4 induced by soluble ICs. However pertussis toxin treatment minimally inhibited the LTB4 release induced by insoluble ICs. Crosslinking of either Fc gamma RII and Fc gamma RIII receptors on neutrophil surfaces induced LTB4 release. This is the first experimental observation showing that both Fc gamma RII and Fc gamma RIII directly induce neutrophil LTB4 metabolism in the absence of exogenous AA. These studies also suggest the involvement of novel pertussis toxin insensitive signal transduction pathways in insoluble ICs stimulation of neutrophils.

Neutrophil-induced liver cell injury in endotoxin shock is a CD11b/CD18-dependent mechanism

To investigate the role of neutrophils (PMNs) and PMN-dependent adhesion molecules in the pathogenesis of liver injury in a model of endotoxin shock, male ICR mice received a dose of 700 mg/kg galactosamine and 100 micrograms/kg Salmonella abortus equi endotoxin. PMNs accumulated continuously in the liver, reaching values of 446 +/- 71 PMNs/50 high-power fields at 9 h (basal value 18 +/- 7). Plasma alanine aminotransferase activities as index of parenchymal cell injury did not change up to 5 h posttreatment (basal value 35 +/- 5 U/l) but increased to 1,950 +/- 460 U/l at 9 h. The formation of glutathione disulfide (GSSG) in plasma as an index of an extracellular oxidant stress also increased only at 9 h. Pretreatment of animals with monoclonal antibodies against the CD11b and CD18 subunits of the CD11/CD18 integrin family on the surface of the PMN reduced the number of PMNs in the liver by 50% and significantly attenuated liver injury and GSSG formation. An anti-CD11a and a nonbinding control antibody were ineffective. It is concluded that PMNs are actively involved in the pathogenesis of galactosamine and endotoxin shock and that at least in part the accumulation of PMNs, the subsequent oxidant stress, and the tissue injury in this model of experimental hepatitis are CD11b/CD18 (Mac-1) dependent.

Hydrogen peroxide pretreatment of perfused canine vessels induces ICAM-1 and CD18-dependent neutrophil adherence

BACKGROUND

Cytotoxic products of neutrophils (polymorphonuclear leukocytes, PMNs) contribute to ischemia-reperfusion injury of several tissues. Hydrogen peroxide (H2O2), one of the cytotoxic products of PMNs, also promotes the adherence of PMNs to cultured vascular endothelial cells in vitro. The present study was undertaken to determine if H2O2 also augmented adhesion of PMNs to intact vessels perfused ex vivo and to determine if H2O2-induced PMN adherence to intact canine carotid arteries and external jugular veins or to cultured canine venous endothelium is mediated by specific adherence ligands on the neutrophil and/or the endothelium.

METHODS AND RESULTS

Vessels were perfused for 20 minutes with oxygenated Krebs-Henseleit bicarbonate buffer with and without H2O2, washed with buffer alone, and then exposed to 111In-labeled isolated PMNs (10(7) cells/vessel) under static conditions for up to 20 minutes before being washed again. Residual radioactivity retained by the washed vessel was counted as an index of PMN retention. The adherence of unlabeled PMNs to cultured endothelial cells was determined by a visual assay method after pretreatment of the endothelium with H2O2 for brief periods followed by washing. Perfusion of vessels with H2O2 produced a transient, concentration-dependent increase in PMN adhesion to both canine carotid arteries and external jugular veins that was two to four times that of control values at 1 mmol/l and declined at higher H2O2 concentrations. Peak retention of PMNs by canine carotid arteries occurred 10 minutes after exposure to 1 mmol/l H2O2 and then rapidly declined to control values; this effect was replicated by a second 20-minute exposure of canine carotid arteries to 1 mmol/l H2O2 60 minutes after the first exposure. Scanning and transmission electron microscopy revealed not only adherence of PMNs to but migration through the vascular endothelium of the carotid artery after H2O2 perfusion. The endothelium was intact in H2O2-treated arteries not exposed to PMNs. H2O2-induced PMN retention was completely inhibited by addition of catalase or the hydroxyl radical scavenger dimethylthiourea to the perfusate by incubation of the PMN with a monoclonal antibody (Mab) against CD18 (R15.7) or by perfusion of the H2O2-treated vessel with CL18/6, a Mab against canine ICAM-1 (intercellular adhesion molecule-1). Similar effects of Mabs on PMN adhesion to H2O2-pretreated cultured endothelium were noted. The retention of PMNs by vessels mechanically denuded of endothelial cells was markedly increased. H2O2 pretreatment of these vessels did not further augment PMN adherence, and no inhibitory effect of R15.7 was noted. Incubation of carotid arteries and PMNs with a specific platelet-activating factor antagonist, WEB2086, completely inhibited the H2O2-induced increased PMN retention by these vessels.

CONCLUSIONS

These results indicate that H2O2 in the absence of evidence for permanent endothelial cell injury, can induce a transient, reversible, platelet-activating factor-dependent adherence of PMNs to vessels by mechanisms that depend on an intact endothelium and involve CD18 on the PMN and ICAM-1 on the endothelium.

Monoclonal antibodies to leukocyte integrins CD11a/CD18 and CD11b/CD18 or intercellular adhesion molecule-1 inhibit chemoattractant-stimulated neutrophil transendothelial migration in vitro

Intercellular adhesion molecule-1 (ICAM-1) is present on the endothelium and binds to one or more members of the CD11/CD18 family of leukocyte surface integrins. To assess the role of these molecules in mediating chemotaxis of neutrophils across the endothelium, an in vitro model consisting of monolayers of human umbilical vein endothelial cells (HUVEC) grown on amniotic connective tissue was used. Neutrophils placed on the apical sides of these cultures migrated across the endothelium in response to chemoattractants added basally. Monoclonal antibodies (MoAbs) to CD11a, CD11b, and CD18 on the neutrophils inhibited this migration by 52% +/- 11%, 29% +/- 19%, and 90% +/- 7%, respectively. An MoAb to ICAM-1 inhibited transendothelial chemotaxis of the leukocytes by 55% +/- 16%. Inhibition was mediated by binding of the MoAb to ICAM-1 on the HUVEC, rather than by any direct effect of the antibody on the neutrophils. When used in combination, MoAbs to CD11a and to CD11b inhibited migration in a nearly additive fashion. A similar additive effect was observed when MoAbs to CD11b and to ICAM-1 were used together. In contrast, MoAbs to CD11a and to ICAM-1 produced no more inhibition when used in combination than when added singly. These results show that ICAM-1, CD11a/CD18, and CD11b/CD18 all participate in controlling migration of neutrophils across endothelial monolayers in response to chemotactic agents.

Canine neutrophil margination mediated by lectin adhesion molecule-1 in vitro

The contributions of the canine neutrophil lectin adhesion molecule-1 (LECAM-1) (canine homologue of the murine MEL-14 Ag) in neutrophil-endothelial cell adhesion and transendothelial migration were studied using anti-LECAM-1 mAb, CL2/6, and SL1 under static conditions and at wall shear stresses of up to 1.85 dynes/cm2 (dpc). Both mAb were found to inhibit attachment of neutrophils to cytokine-stimulated canine jugular vein endothelium. The inhibitory effects of the anti-LECAM-1 mAb were more evident at a wall shear stress of 1.85 dpc (greater than 50%) than at 0.23 dpc or under static conditions (approximately 30%). In contrast the anti-CD18 mAb, R15.7, exhibited higher inhibitory ability at the lower shear stress and under static conditions with marginal inhibition of adhesion at 1.85 dpc. Anti-LECAM-1 and anti-CD18 mAb showed additive inhibitory effects at the lower wall shear stress and under static conditions. Chemotactic stimulation of the neutrophils caused rapid down-regulation of LECAM-1 from the neutrophil surface and reduced adhesion by 60% at a wall shear stress of 1.85 dpc. This inhibition was not additive to anti-LECAM-1 mAb. Pretreatment with CL2/6 or SL1 did not affect trans-endothelial migration of adherent neutrophils under any experimental conditions tested. Anti-CD18 mAb, however, blocked transendothelial migration by 98% and 56% under static condition and at a wall shear stress of 0.23 dpc, respectively. The results in this report indicate that canine LECAM-1 is involved in the initial adhesion of unstimulated neutrophils to cytokine-stimulated endothelial cells under flow, but in contrast to CD18-integrins, plays no role in the transendothelial migration.

Endothelial leukocyte adhesion molecule-1 mediates antigen-induced acute airway inflammation and late-phase airway obstruction in monkeys

This study examines the role of endothelial leukocyte adhesion molecule-1 (ELAM-1) in the development of the acute airway inflammation (cell influx) and late-phase airway obstruction in a primate model of extrinsic asthma. In animals sensitive to antigen, a single inhalation exposure induced the rapid expression of ELAM-1 (6 h) exclusively on vascular endothelium that correlated with the influx of neutrophils into the lungs and the onset of late-phase airway obstruction. In contrast, basal levels of ICAM-1 was constitutively expressed on vascular endothelium and airway epithelium before antigen challenge. After the single antigen exposure, changes in ICAM-1 expression did not correlate with neutrophil influx or the change in airway caliber. This was confirmed by showing that pretreatment with a monoclonal antibody to ICAM-1 did not inhibit the acute influx of neutrophils associated with late-phase airway obstruction, whereas a monoclonal antibody to ELAM-1 blocked both the influx of neutrophils and the late-phase airway obstruction. This study demonstrates a functional role for ELAM-1 in the development of acute airway inflammation in vivo. We conclude that, in primates, the late-phase response is the result of an ELAM-1 dependent influx of neutrophils. Therefore, the regulation of ELAM-1 expression may provide a novel approach to controlling the acute inflammatory response, and thereby, affecting airway function associated with inflammatory disorders, including asthma.

Canine neutrophil margination mediated by lectin adhesion molecule-1 in vitro

The contributions of the canine neutrophil lectin adhesion molecule-1 (LECAM-1) (canine homologue of the murine MEL-14 Ag) in neutrophil-endothelial cell adhesion and transendothelial migration were studied using anti-LECAM-1 mAb, CL2/6, and SL1 under static conditions and at wall shear stresses of up to 1.85 dynes/cm2 (dpc). Both mAb were found to inhibit attachment of neutrophils to cytokine-stimulated canine jugular vein endothelium. The inhibitory effects of the anti-LECAM-1 mAb were more evident at a wall shear stress of 1.85 dpc (greater than 50%) than at 0.23 dpc or under static conditions (approximately 30%). In contrast the anti-CD18 mAb, R15.7, exhibited higher inhibitory ability at the lower shear stress and under static conditions with marginal inhibition of adhesion at 1.85 dpc. Anti-LECAM-1 and anti-CD18 mAb showed additive inhibitory effects at the lower wall shear stress and under static conditions. Chemotactic stimulation of the neutrophils caused rapid down-regulation of LECAM-1 from the neutrophil surface and reduced adhesion by 60% at a wall shear stress of 1.85 dpc. This inhibition was not additive to anti-LECAM-1 mAb. Pretreatment with CL2/6 or SL1 did not affect trans-endothelial migration of adherent neutrophils under any experimental conditions tested. Anti-CD18 mAb, however, blocked transendothelial migration by 98% and 56% under static condition and at a wall shear stress of 0.23 dpc, respectively. The results in this report indicate that canine LECAM-1 is involved in the initial adhesion of unstimulated neutrophils to cytokine-stimulated endothelial cells under flow, but in contrast to CD18-integrins, plays no role in the transendothelial migration.

Role of endothelial-leukocyte adhesion molecule 1 (ELAM-1) in neutrophil-mediated lung injury in rats

Two murine monoclonal antibodies (CL-3 and CL-37, both F(ab')2) to human endothelial-leukocyte adhesion molecule-1 (ELAM-1) were found to react immunohistochemically with rat pulmonary artery endothelial cells that had been pretreated with tumor necrosis factor (TNF alpha). CL-3, but not CL-37, blocked in vitro adherence of neutrophils to TNF alpha-treated endothelial cells and the killing of TNF alpha-treated rat endothelial cells by phorbol ester activated neutrophils. In rats treated systemically with CL-3, there was a 70% reduction in accumulation of neutrophils in glycogen-induced peritoneal exudates. Treatment of animals with CL-37 anti-ELAM-1 did not reduce neutrophil accumulation under the same conditions. When IgG immune complex deposition was induced in dermis and in lungs of rats, treatment with CL-3 anti-ELAM-1 markedly reduced vascular injury as measured by changes in vascular permeability (leakage of 125I-albumin) and hemorrhage (extravasation of 51Cr-red blood cells). The protective effects of CL-3 anti-ELAM-1 were related to greatly diminished recruitment of neutrophils (as assessed morphologically, by tissue extraction of myeloperoxidase, and by retrieval, via bronchoalveolar lavage, of neutrophils from lung). CL-37 had no protective effects in vivo after deposition of immune complexes in lung. Using either CL-3 or CL-37 anti-ELAM-1, immunohistochemical analysis of lungs undergoing IgG immune complex-induced injury revealed a striking upregulation of ELAM-1 in the lung vasculature (venules and interstitial capillaries), with a peak intensity developing between 3 and 4 h after deposition of immune complexes in lung. Vascular beds of spleen, liver, and kidney failed to show upregulation of ELAM-1 under these same conditions. The immunohistochemical reactivity of rat lung was abolished if the anti-ELAM-1 preparation was first absorbed with monolayers of human umbilical vein endothelial cells that had been pretreated with TNF alpha. Untreated human endothelial cells failed to cause loss of lung reactivity of the anti-ELAM-1 preparation. These data indicate that ELAM-1 is upregulated in the pulmonary vasculature of rats during deposition of immune complexes and that ELAM-1 appears to play an obligate role in the recruitment of neutrophils.

Adherence of neutrophils to canine cardiac myocytes in vitro is dependent on intercellular adhesion molecule-1

The adhesiveness of isolated canine cardiac myocytes for neutrophils is greatly increased by stimulation with cytokines such as tumor necrosis factor alpha (TNF alpha). Since this adhesion is significantly inhibited by an anti-CD18 MAb, experiments were performed to test the hypothesis that the newly expressed adhesion molecule on the cardiac myocytes was intercellular adhesion molecule-1 (ICAM-1). A newly developed MAb, CL18/6, was found to exhibit the functional and binding characteristics with canine neutrophils and canine jugular vein endothelial cells expected of an antibody recognizing ICAM-1. MAb CL18/6 also bound to isolated cardiac myocytes after stimulation of the myocytes with cytokines, and it blocked by greater than 90% the adhesion of neutrophils to stimulated myocytes. A partial cDNA clone for canine ICAM-1 was isolated, and ICAM-1 mRNA was found to be increased in both endothelial cells and cardiac myocytes after cytokine stimulation. Cytokines that both increased the CL18/6-inhibitable adhesion of neutrophils to myocytes and induced expression of ICAM-1 were IL-1 beta, TNF alpha, and LPS. These results are consistent with the conclusion that canine endothelial cells and cardiac myocytes express ICAM-1 in response to cytokine stimulation, and that ICAM-1 functions as an adhesive molecule for neutrophils on both cell types.

Inflammation in the course of early myocardial ischemia

Experimental models of acute ischemic myocardial injury indicate that the inflammatory response after the ischemic event contributes to tissue damage. This is especially apparent with reperfusion of the ischemic tissue. In such models some therapeutic strategies designed to reduce neutrophil accumulation or function have resulted in apparently beneficial effects. Although such findings are encouraging, interventions into these pathological processes using specific molecular targets will require greater understanding of specific mechanisms. Current evidence indicates that potential sites of therapeutic intervention will be found in pathways leading to complement activation, generation of lipid-derived mediators, adhesion of neutrophils to endothelial cells and cardiac myocytes, and activation of neutrophil secretory processes releasing, for example, proteolytic enzymes and reactive oxygen. Understanding the dynamic interplay between the mediators, adhesion pathways, and secretory processes that results in myocardial damage will allow a rational approach to controlling the detrimental inflammatory consequences of ischemia and reperfusion.

Antibodies against human neutrophil LECAM-1 (LAM-1/Leu-8/DREG-56 antigen) and endothelial cell ELAM-1 inhibit a common CD18-independent adhesion pathway in vitro

Neutrophil adhesion to interleukin-1 (IL-1)-stimulated human umbilical vein endothelial cells (HUVEC) involves the CD18 family of leukocyte integrins (lymphocyte function-associated antigen-1 [LFA-1], Mac-1, and p150,95) and LECAM-1 (DREG-56/LEU-8/LAM-1 antigen) on neutrophils and intercellular adhesion molecule-1 (ICAM-1) and endothelial leukocyte adhesion molecule-1 (ELAM-1) on the endothelium. In this study, we compare CD18-independent adhesion pathways mediated by neutrophil LECAM-1 and endothelial ELAM-1 and find that these two pathways overlap in a variety of assays: (1) anti-LECAM-1 and anti-ELAM-1 monoclonal antibody (MoAb) inhibit neutrophil binding to HUVEC, and the inhibitory effect is not additive; (2) anti-LECAM-1 MoAb, like anti-ELAM-1 MoAb, inhibits neutrophil binding to HUVEC stimulated for 3 hours with IL-1, but not to HUVEC stimulated for 8 hours, by which time ELAM-1 expression is downregulated; (3) anti-ELAM-1 MoAb has no effect on transendothelial migration, a CD18-dependent, LECAM-1-independent neutrophil function. Interestingly, anti-ELAM MoAb has a reduced but significant inhibitory effect on the adhesion of activated neutrophils that have shed their cell-surface LECAM-1. We also show that neutrophil binding to ELAM-1-transfected L cells is inhibited not only by anti-ELAM-1 but also by anti-LECAM-1 MoAb. These results suggest that LECAM-1 and ELAM-1 can operate in the same adhesion pathway, possibly as a receptor-counterreceptor pair. LECAM-1 and ELAM-1 are likely to interact with other ligands as well, perhaps through carbohydrate determinants that modify more than one glycoprotein.

Immunodominant T-cell epitope on the F protein of respiratory syncytial virus recognized by human lymphocytes

The lymphocyte proliferative responses to respiratory syncytial virus (RSV) were evaluated for 10 healthy adult donors and compared with proliferative responses to a chimeric glycoprotein (FG glycoprotein) which consists of the extracellular domains of both the F and G proteins of RSV and which is produced from a recombinant baculovirus. The lymphocytes of all 10 donors responded to RSV, and the proliferative responses to the whole virus were highly correlated with the responses to the FG glycoprotein. These data suggested that one or both of these glycoproteins of RSV were major target structures for stimulation of the human lymphocyte proliferative response among virus-specific memory T cells. The lymphocytes of four donors were evaluated further for their proliferative responses to a nested set of overlapping peptides modeled on the extracellular and cytoplasmic domains of the F protein of RSV. Strikingly, the lymphocytes of all 4 donors responded primarily to a region defined by a single peptide spanning residues 338 to 355, and the lymphocytes of 2 donors responded to an overlapping peptide spanning residues 328 to 342 also, thus defining a region of the F1 subunit within residues 328 to 355 that may circumscribe an immunodominant site for stimulation of human T cells from a variety of individuals. This region of the F protein is highly conserved among A and B subgroup viruses. As revealed by monoclonal antibody blocking studies, the lymphocytes responding to this antigenic site had characteristics consistent with T helper cells. Similar epitope mapping studies were performed with BALB/c mice immunized with the FG protein in which a relatively hydrophobic peptide spanning residues 51 to 65 within the F2 subunit appeared to be the major T cell recognition determinant. The data are discussed with respect to an antigenic map of the F protein and the potential construction of a synthetic vaccine for RSV.

Neutrophil accumulation in ischemic canine myocardium. Insights into time course, distribution, and mechanism of localization during early reperfusion

BACKGROUND

We have previously demonstrated that chemotactic factors released from the ischemic canine myocardium peak early during reperfusion and that they elicit neutrophil adherence reactions in vitro that are dependent on the CD18 glycoprotein family. In this study we investigated the hypothesis that neutrophil localization in ischemic canine myocardium in vivo occurs over a similar time course during early reperfusion and involves a CD18-dependent mechanism.

METHODS AND RESULTS

We occluded the circumflex coronary artery for 1 hour in acute, open-chest dogs, followed by reperfusion for 1, 2, 3, or 4 hours. Regional myocardial blood flow was determined using radiolabeled microspheres, and localization was traced using technetium-99m-labeled autologous neutrophils. In the first hour of reperfusion, neutrophil localization occurred preferentially within the subendocardial region and was inversely related to flow. Neutrophil localization diminished across the ischemic myocardium from endocardium to epicardium but remained negatively related to flow in the midmyocardial region. Regardless of flow, little neutrophil localization occurred in the subepicardial region. Neutrophil localization was greatest in the first hour of reperfusion and diminished thereafter. By 4 hours of reperfusion, the rate of localization was markedly attenuated relative to 1 hour. Dogs given anti-CD18 monoclonal antibody R15.7 (1 mg/kg i.v.) before occlusion underwent 1 hour of occlusion followed by 1 hour of reperfusion. When compared with 1-hour reperfusion controls, the R15.7-treated dogs demonstrated significant attenuation of neutrophil localization in the subendocardial region.

CONCLUSIONS

These data support the concepts that rapid neutrophil localization during reperfusion occurs within regions of previous myocardial ischemia and that neutrophils preferentially localize within the subendocardial region. The rate of neutrophil localization is greatest within the first hour after the initiation of reperfusion, and localization is, at least in part, CD18 dependent. Therapies directed against neutrophil-mediated reperfusion injury should be initiated with these considerations in mind.

Exercise. Practical treatment for the patient with depression and chronic fatigue

Exercise should be part of everyone's lifestyle, but may be a particularly important part of the treatment of patients with depression and chronic fatigue. It will reliably and consistently decrease feelings of tiredness and despondency, although it is seldom sufficient as a sole treatment intervention for such patients. When initiating an exercise program, a baseline assessment should be followed by an exercise prescription and an appropriate degree of patient education about exercise physiology. This should be followed, in addition to other treatment interventions, by regular follow-up visits to make appropriate adjustments; provide encouragement and motivation to continue; monitor weight, body fat, and nutrition; and assess the effectiveness of the program on the underlying problem.

Diminished lectin-, epidermal growth factor-, complement binding domain-cell adhesion molecule-1 on neonatal neutrophils underlies their impaired CD18-independent adhesion to endothelial cells in vitro

To define further the molecular basis for abnormal interactions of cord blood or neonatal neutrophils with endothelial cells in vitro, we studied neutrophil adhesion and migration under experimental conditions specifically designed to evaluate CD18-independent mechanisms. Unstimulated cord blood neutrophils of healthy term neonates demonstrated significantly diminished adhesion to IL-1-stimulated endothelial cell monolayers under conditions of shear stress (congruent to 1.85 dynes/cm2); overall levels of migration by neonatal cells were also significantly diminished, although the adherent subpopulation of these cells migrated relatively normally. A mAb (DREG-56) against the human homologue of the murine MEL-14 antigen (termed lectin-, epidermal growth factor-, complement binding domain-cell adhesion molecule-1 (LECAM-1), a member of the LEC-CAM family of adhesion molecules) markedly inhibited adhesion of healthy adult but not cord blood neutrophils. In additional assessments of endothelial cell adhesion or migration in the absence of shear forces, cord blood neutrophils demonstrated significantly diminished values compared to adult controls. Moreover, mAb DREG-56 significantly diminished adhesion of healthy adult but not cord blood suspensions in the presence or absence of the anti-CD18 mAb R15.7. Immunofluorescence assessments of unstimulated cord blood neutrophils or neutrophils of neonates 12 to 48 h of age showed dramatically diminished levels of surface LECAM-1 compared to adult neutrophils. Chemotactic stimuli (FMLP, 10 nM, 15 min) consistently "down-regulated" surface LECAM-1 on adult neutrophils to levels approximately 10% of unstimulated suspensions and comparable to those of most unstimulated neonatal suspensions. Moreover, FMLP stimuli elicited little or no down-regulation of LECAM-1 on neonatal cells. In comparative studies, endothelial cell adhesion of unstimulated cord blood or adult control neutrophils (assessed under conditions of flow) was directly related to levels of neutrophil surface LECAM-1. Although FMLP stimulation significantly diminished both adhesion and LECAM-1 surface levels of adult control cells, the adhesion and LECAM-1 expression observed with cord blood cells were not significantly influenced by this stimulus. The mechanisms underlying diminished LECAM-1 expression and LECAM-1-dependent adhesion of neonatal neutrophils and the physiologic significance of these abnormalities deserve investigation.