A phase I trial of immunosuppression with anti-ICAM-1 (CD54) mAb in renal allograft recipients

Acute renal failure: role of dialysis membrane biocompatibility

Recent clinical studies of acute renal failure in adults have focused attention on the biocompatibility of the dialysis membrane as a possible factor influencing patient morbidity and mortality. In this article, we review the concept of dialysis membrane biocompatibility and highlight the difficulty of finding an ideal definition. We then expand on the possible roles of complement and neutrophil activation by dialysis membranes, which may prolong the recovery from acute renal failure. The results of several clinical studies analyzing the impact of dialysis membranes on the course and outcome of acute renal failure are discussed. Finally, the possible relevance of biocompatibility in continuous renal replacement therapies is emphasized.

A randomized multicenter trial comparing leukocyte function-associated antigen-1 monoclonal antibody with rabbit antithymocyte globulin as induction treatment in first kidney transplantations

Adhesion molecules are involved in several steps in the immune response: leukocyte adhesion to the endothelium, transendothelial migration, cooperation between immunocompetent cells, and cytotoxicity. Leukocyte function-associated antigen-1 plays a central role among adhesion molecules. In a multicenter randomized open trial, we compared a monoclonal antibody directed against the alpha chain of LFA-1 (Oduli-momab; IMTIX/Pasteur Mérieux Sérums et Vaccins) with rabbit antithymocyte globulin (rATG; IMTIX/Pasteur Mérieux Sérums et Vaccins), as part of a quadruple sequential protocol in 101 patients receiving a first kidney transplant. Clinical tolerance of anti-LFA-1 mAb was better than that of rATG. Short-term rejection rates (< 15 days) were not significantly different (15% and 16% for anti-LFA-1 mAb and rATG, respectively). However, 11% of the anti-LFA-1 mAb patients experienced rejection during the first 10 days of the treatment course compared with none of the patients treated with rATG. The incidence and severity of acute rejection in the first 3 months was not significantly different between groups. Of the LFA-1 and rATG patients, 96% and 92% of the grafts, respectively, were functioning at 12 months. The incidence and severity of infection, whatever the origin, were comparable in both groups. In addition, it was observed that fewer patients required posttransplantation dialysis in the anti-LFA-1 mAb group (19%, vs. 35% for rATG), although the difference was not statistically significant. Altogether, the beneficial action of this monoclonal antibody on short-term renal function recovery makes it a useful tool in the management of renal patients undergoing kidney transplantation.

Castanospermine, an oligosaccharide processing inhibitor, reduces membrane expression of adhesion molecules and prolongs heart allograft survival in rats

The inhibition of intracellular oligosaccharide processing is a new approach to immunosuppression in allotransplantation. The net effect of such inhibition is reduction in the membrane expression of certain glycoproteins. Hence cell-cell interaction in allorejection may be impaired in the presence of glycoprotein processing inhibitors because the expression of key ligand-receptor pairs of N-linked glycoproteins including adhesion molecules is inhibited. The aims of this study were to measure the immunosuppressive ability of castanospermine (CAST) in a rat heart allograft model, to measure its effect on membrane expression of adhesion molecules (LFA-1 alpha, LFA-1 beta, ICAM-1), class I and class II MHC antigens and on other T cell associated molecules (CD4, CD8, CD39, CD45, W3/13), to test its tolerogenic potential and its toxicity. Membrane expression of these molecules was measured by flow cytometry for single cells and by immunoperoxidase staining for the allograft. In grafted rats CAST significantly reduced the expression of LFA-1 alpha on lymphoid cells in the thymus, lymph node, spleen and heart allografts. ICAM-1 expression on endothelial cells of the allograft vasculature, class I and class II MHC expression on lymphoid cells in the thymus, class II MHC expression on lymphoid cells in the allograft; and CD4, CD8, CD45 and W3/13 expression on lymphoid cells in some organs. By contrast, in non-grafted rats CAST significantly upregulated expression of class I MHC and CD45 in the thymus, lymph node and spleen, ICAM-1 and CD4 on lymphoid cells in the spleen, but reduced expression of LFA-1 alpha on lymphoid cells in the thymus. It also prolonged rat heart allograft survival in a dose-dependent manner and with limited testing was relatively non-toxic. In conclusion, CAST is an immunosuppressive molecule which may work by downregulation of the ligand-receptor adhesion molecule pair, LFA-1 alpha-ICAM-1 although subtle downregulation of class I and II MHC, CD4 and CD8 molecules could also contribute to its immunosuppressive activity. Hence, both lymphocyte-endothelial cell binding and lymphocyte activation may be inhibited by CAST. This work suggests that CAST may hold significant potential as a transplant immunosuppressant probably as an adjuvant agent to inhibitors of interleukin 2 secretion.

Attenuation of rat lung isograft reperfusion injury with a combination of anti-ICAM-1 and anti-beta2 integrin monoclonal antibodies

Four different combinations of monoclonal antibodies against rat ICAM-1, CD-11a, and CD-18 were utilized to determine the relative importance of LFA-1, Mac-1, and ICAM-1 in a rat model of severe lung allograft reperfusion injury. Negative control animals were given phosphate buffered saline (the carrier solution for the antibodies), while positive control animals were rendered neutropenic by the administration of a polyclonal mouse IgG. Antibodies were given with the donor lung flush, prior to left lung graft reperfusion, or both. Isolated graft function was determined 24 hr after implantation by arterial blood gas (ABG), and after sacrifice the native and transplanted lungs underwent bronchoalveolar lavage for alveolar protein quantitation, cell count and differential, and myeloperoxidase assay. Additionally, whole lung homogenates were assayed for myeloperoxidase activity. We found that the combination of anti-ICAM-1 (1 mg/kg) added to the donor lung flush, and anti-CD11a, anti-CD18, and anti-ICAM-1 (2 mg/kg i.v. of each) given to the recipient prior to reperfusion, resulted in significantly improved lung graft pAO2 by ABG, and decreased alveolar protein, cell count, and myeloperoxidase activity compared with control animals. Improvement was less than that seen in the neutropenic recipients, however. We conclude that LFA-1, Mac-1, and ICAM-1 are all important adhesion molecules in lung allograft reperfusion injury--yet even with antibody blockade of all three there are additional mechanisms allowing for neutrophil influx into the lungs.

Experimental antileukocyte interventions in cerebral ischemia

White blood cells (WBCs) play vital roles in host defense. Recently, increasing interest has been directed toward the question of whether WBCs, particularly polymorphonuclear leukocytes, could also act as mediators of secondary brain damage in the setting of focal and global cerebral ischemia with and without reperfusion. Considerable insight into the importance of WBC-mediated tissue injury has been gained from studies employing antileukocyte interventions in experimental cerebral ischemia. The purpose of this article is to survey the different approaches taken to interfere with WBC inflammatory function. Emphasis is laid on a discussion of the efficacy of these interventions, their effects and side effects on cerebral and systemic parameters, and the power of evidence they provide for identification of WBCs as important factors in cerebral ischemia. The role of WBCs has been investigated in a great variety of global and focal cerebral ischemia models with and without reperfusion, leading to sometimes contradictory results. In the light of currently available data, it seems likely that WBCs contribute to secondary brain damage in the scenario of experimental transient focal cerebral ischemia, if the insult is not too severe.

Long-term survival of solid organ allografts by brief anti-lymphocyte function-associated antigen-1 monoclonal antibody monotherapy

Strategies targeting lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18) and intercellular adhesion molecule-1 (ICAM-1) have previously been shown to produce long-term survival of solid organ allografts in animals only when both CD11a and ICAM-1 are targeted for a brief (6-7 days) time or when extended (14 weeks) treatment with anti-CD11a monoclonal antibody (mAb) is administered. We show that recipient pretreatment followed by a brief (13 days) treatment course with high-dose anti-CD11a mAb alone produces long-term survival of cardiac allografts in the rigorous, nonprimarily vascularized heart allograft model in mice. This treatment regimen induces specific unresponsiveness in our model. In recipients bearing long-term beating cardiac grafts after treatment with anti-CD11a mAb, there still exists a high frequency of potentially antigen-reactive T cells in isolated peripheral blood lymphocyte fractions. Therefore, clonal deletion does not appear to explain the induction of specific unresponsiveness by treatment with anti-CD11a mAb in this model. These findings support the further investigation of the use of high-dose anti-LFA-1 mAb monotherapy in the pre- and early postoperative period to promote solid organ allograft survival.

Antisense oligonucleotides for ICAM-1 attenuate reperfusion injury and renal failure in the rat

The leukocyte adhesion molecule ICAM-1 is implicated in ischemic renal reperfusion injury. We tested the utility of an ICAM-1 antisense oligodeoxyribonucleotide (ODN) with lipofectin, six hours prior to 30 minutes of bilateral renal ischemia in the rat. We measured ICAM-1 expression by immunohistochemistry and Western blot. Our antisense ODN showed a specific ICAM-1 surface expression inhibition in vitro. We then assessed ICAM-1 expression, leukocyte infiltration, serum creatinine, serum urea concentration, and renal histology in rats subjected to renal ischemia and controls. Serum creatinine and urea concentrations 12 and 24 hours post-ischemia were increased in saline treated and reverse ODN treated rats, compared to antisense ODN treated or sham operated rats (P < 0.05). Western blotting showed decreased ICAM-1 protein in antisense ODN-treated kidneys, compared to reverse ODN treated and saline treated ischemic controls (P < 0.05). Antisense ODN also ameliorated the ischemia-induced infiltration of granulocytes and macrophages (P < 0.05), and resulted in less cortical renal damage as assessed by a quantitative pathological grading scale (P < 0.05), compared to reverse ODN or saline treatment. Thus, antisense ODN for ICAM-1 protected the kidney against ischemic renal failure. The clinical applicability of these findings extends beyond ischemic acute renal failure.

Immunosuppression by anti-ICAM-1 and anti-LFA-1 monoclonal antibodies of free and vascularized skin allograft rejection

Immunosuppression by anti-adhesion molecule antibody of free or vascularized skin allograft rejection was investigated in rats. Lewis (LEW, RT11) rats were used as donors and Fisher (F344, RT11v1) rats as the recipients. When F344 rats were treated intraperitoneally (i.p.) with anti-intercellular adhesion molecule-1 (ICAM-1) mAb (1A29) (3 mg/kg/day) and anti-leukocyte function-associated antigen-1 (LFA-1) mAb (WT.1) (3 mg/kg/day) one day prior to grafting and daily after grafting for nine days, free skin graft survival was prolonged only slightly compared with that in control rats which were injected i.p. with a daily dose of 6 mg/kg of anti-TNP mAbs (H1-6-2) one day prior to grafting and daily after grafting for nine days. (Mean survival time [MST] of the free skin graft was 11.2 +/- 0.6 days in the control group and 13.4 +/- 0.3 days in the 1A29 + WT-1 treated group [p < 0.01], respectively.) On the other hand, the vascularized graft survival was prolonged significantly in anti-ICAM-1/LFA-1 mAbs-treated F344 rats as compared with that in control rats. (The mean vascularized graft survival time was 14.2 +/- 0.7 days in the control group and 21.5 +/- 1.9 days in 1A29 + WT-1 treated group [p < 0.002]). Our results suggest that interaction with ICAM-1 and LFA-1 is more important in the rejection of vascularized skin allografts than that of free skin allografts.

The significance of adhesion molecules in nephrology

Our knowledge of adhesion molecules has exploded over the last 5 years and has swamped most fields of medicine including nephrology. This is not surprising because adhesion molecules play a pivotal role in all aspects of cell to cell contact. Thus, they are involved in important issues, such as fetal development, in any kind of inflammatory or immune response including allograft rejection, as well as thrombus formation, and in tumor growth and metastasis (1-3). This short overview briefly reports some aspects of the biology of relevant adhesion molecules and their significance in inflammatory kidney diseases and in hemodialysis and renal allograft rejection. Finally, new therapeutic opportunities that arise by blocking adhesion molecule function are discussed.

Ibuprofen inhibits pyrogen-dependent expression of VCAM-1 and ICAM-1 on human endothelial cells

Leukocyte adhesion and transmigration through the endothelial cell (EC) layer plays a crucial role in inflammation. IL-1 alpha and TNF alpha increase EC-adhesiveness for leukocytes by stimulating surface expression of ICAM-1 (intercellular adhesion molecule 1, CD54), VCAM-1 (vascular cell adhesion molecule 1, CD106) and E-selectin (CD62E). In this study, the effects of ibuprofen on IL-1 alpha and TNF alpha-induced expression of ICAM-1, VCAM-1 and E-selectin on cultured human umbilical vein EC (HUVEC) were analyzed. Exposure to IL-1 alpha or TNF alpha resulted in an increased expression of VCAM-1, ICAM-1, and E-selectin. Ibuprofen was identified as a potent inhibitor of IL-1 alpha and TNF alpha-induced surface expression of VCAM-1 and a less potent inhibitor of pyrogen-induced expression of ICAM-1, whereas no effect on E-selectin was found. The effects of ibuprofen on VCAM-1 expression were dose-dependent (IC50 [IL-1 alpha]: 0.5 mM; IC50 [TNF alpha]: 0.5 mM) and time-dependent with maximum responses observed after 18 h. Moreover, ibuprofen abrogated pyrogen-dependent adhesion of leukocytes to HUVEC. Ibuprofen also inhibited VCAM-1 mRNA expression in pyrogen activated EC. VCAM-1-downregulation on EC by ibuprofen may contribute to the anti-inflammatory actions of the drug.

Adhesion molecules as determinants of disease: from molecular biology to surgical research

Cellular adhesion is mediated by distinct cell surface receptors (adhesion molecules) and plays a pivotal role in the biological processes of morphogenesis, cell migration and cell-cell communication. During the past decade many adhesion molecules have been identified and structurally analysed. This has allowed an understanding of their role in the pathophysiology of disease, including inflammation and sepsis, ischaemia and reperfusion, transplant rejection, atherosclerosis and thrombosis, angiogenesis and wound healing, as well as carcinogenesis and tumour metastasis. Understanding of the molecular mechanisms of cellular communication is not only vital for advances in surgical pathophysiology, it also has the potential to widen the spectrum of diagnosis and therapy of disease. Analysis of expression of individual surface molecules may help in the diagnosis of transplant rejection and allow a prognostic determination of tumour progression and metastasis formation. Moreover, manipulation of adhesion molecule function by monoclonal antibodies, antisense oligonucleotides or single gene products may open the door for novel therapeutic regimens to prevent transplant rejection and ischaemia-, sepsis- and shock-induced tissue injury.

Enhanced isolated lung function after ischemia with anti-intercellular adhesion molecule antibody

The binding of leukocytes to intercellular adhesion molecules expressed on endothelial surfaces during ischemia and subsequent reperfusion initiates leukocyte-mediated reperfusion injury. Interruption of this leukocyte-endothelium interaction may therefore prevent reperfusion injury. In an isolated, ventilated, blood-perfused rabbit lung preparation, we studied the effect of a monoclonal anti-intercellular adhesion molecule antibody on lung function during reperfusion. Lungs were harvested with 50 ml/kg cold Euro-Collins flush and 30 micrograms prostaglandin E1 before storage for 18 hours at 4 degrees C. Experimental groups received low-dose (100 micrograms) or high-dose (200 micrograms) anti-intercellular adhesion molecule antibody added to the pulmonary flush at harvest and to the initial reperfusate. Eighteen-hour control preparations were preserved for 18 hours and received saline solution vehicle. Immediate control preparations were harvested and immediately reperfused. The oxygen tension in the recirculated pulmonary venous effluent was measured after 30 minutes of reperfusion. Histologic specimens were graded by blinded observers for degree of leukocyte infiltration (0, normal, to 4, severe infiltration). The mean oxygen tensions (+/-standard error of the mean) were 138.29 +/- 6.23, 58.86 +/- 9.14, 86.87 +/- 11.32, and 139.33 +/- 16.15 mm Hg in immediate control preparations, 18-hour control preparations, low-dose antibody group, and high-dose antibody group, respectively (p = 0.0001). The leukocyte grades (mean +/- standard error of the mean) were 1.5 +/- 0.723, 3.0 +/- 0.955, 1.9 +/- 0.899, and 1.2 +/- 0.834, respectively (p = 0.0002). We conclude that anti-intercellular adhesion molecule antibody added to the pulmonary flush and initial reperfusate results in a dose-dependent enhancement of the reperfused lung's ability to oxygenate blood, possibly as a result of decreased leukocyte sequestration.

A human/mouse chimeric monoclonal antibody against intercellular adhesion molecule-1 for tumor radioimmunoimaging

A mouse-human chimeric antibody for intercellular adhesion molecule-1 (ICAM-1) was established by using heavy chain loss mouse mutant hybridoma and human immunoglobulin expression vector. The HA58 hybridoma secreted anti-ICAM-1 monoclonal antibody (MoAb) (IgG1, kappa). The gene of the mouse variable region of heavy chain was amplified and cloned by the polymerase chain reaction technique directly from the HA58 hybridoma RNA. The variable region of heavy chain was joined with an expression vector which contains human gamma 1 constant gene. The expression vector was transfected into heavy chain loss mutant cells HA58-7, which produced only murine immunoglobulin light chains. The resultant chimeric MoAb HA58, chHA58, retained full-binding reactivity to ICAM-1 compared with murine HA58 parental antibody. The chimeric MoAb chHA58 showed little antibody dependent cell-mediated cytotoxic activity against cultured tumor cells. Biodistribution studies with 99mTc-labeled chHA58 in nude mice bearing human gastric carcinoma JRST cells demonstrated that the tumor-blood ratio was 1.55 at 18 h after injection, when the tumors were clearly visible in gamma scintigraphy. These data suggest that chHA58 may be of practical use for radioimmunoimaging of a wide variety of tumors.

Intercellular adhesion molecule-1-deficient mice are protected against ischemic renal injury

Studies in the rat have pointed to a role for intercellular adhesion molecule-1 (ICAM-1) in the pathogenesis of acute tubular necrosis. These studies used antibodies, which may have nonspecific effects. We report that renal ICAM-1 mRNA levels and systemic levels of the cytokines IL-1 and TNF-alpha increase 1 h after ischemia/ reperfusion in the mouse. We sought direct proof for a critical role for ICAM-1 in the pathophysiology of ischemic renal failure using mutant mice genetically deficient in ICAM-1. ICAM-1 is undetectable in mutant mice in contrast with normal mice, in which ICAM-1 is prominent in the endothelium of the vasa recta. Mutant mice are protected from acute renal ischemic injury as judged by serum creatinine, renal histology, and animal survival . Renal leukocyte infiltration, quantitated morphologically and by measuring tissue myeloperoxidase, was markedly less in ICAM-1-deficient than control mice. To evaluate whether prevention of neutrophil infiltration could be responsible for the protection observed in the mutant mice, we treated normal mice with antineutrophil serum to reduce absolute neutrophil counts to < 100 cells/mm3. These neutrophil-depleted animals were protected against ischemic renal failure. Anti-1CAm-1 antibody protected normal mice against renal ischemic injury but did not provide additional protection to neutrophil-depleted animals. Thus, ICAM-1 is a key mediator of ischemic acute renal failure likely acting via potentiation of neutrophilendothelial interactions.

Adhesion molecules--their role in health and disease

Adhesion molecules play a major role in the recruitment of neutrophils to the site of inflammation. Neutrophils' localization is dynamic and involves multiple steps. In each step a different family of adhesion molecules takes part. The rolling phase is mediated by the selectin family, the E-, L-, and P- selectins, and their ligand, sialyl Lewis X. The next step, the activation and firm adhesion of the neutrophils to the endothelium, is regulated by the integrin family and their ligand, the Ig superfamily. The final step of transendothelial migration is again mediated by these two families of adhesion molecules. Although many in vitro studies were able to show the role of these molecules, their real importance was demonstrated in rare disease states where one of the adhesion molecule was absent. Two adhesion molecule deficiencies were described, both characterized by recurrent infections, defect in wound healing, and marked leukocytosis. Leukocyte adhesion deficiency (LAD) I is caused by a defect in the beta subunit of the integrin molecule, whereas in LAD II, the ligand for the selectin, the sialyl Lewis X is markedly decreased. Further insight was also gained with the generation of strains of mice deficient in one or another adhesion molecules (knock-out mice) Exploiting current knowledge on adhesion molecules and their role in health and disease, several trials have been designed to assess the effect of blocking their activity in conditions associated with increased expression of various adhesion molecules.

Specific acceptance of fetal bowel allograft in mice after combined treatment with anti-intercellular adhesion molecule-1 and leukocyte function-associated antigen-1 antibodies

OBJECTIVE

The aim of this study was to see whether tolerance could be induced by simultaneous administration of monoclonal antibodies (MoAbs) to intercellular adhesion molecule-1 (ICAM-1) and leukocyte function-associated antigen-1 (LFA-1) after transplantation of fetal small bowel between fully incompatible mice strains.

METHODS

Fetal small bowel from either BALB/c (H-2d) or C3H/He (H-2k) mice was transplanted into the space between the peritoneum and rectus abdominis of adult C3H/He recipient mice. Syngeneic (n = 6) and two allogeneic transplant groups were made. In one of the allogeneic groups (n = 8), no immunosuppressant was given. In the other allogeneic group (n = 13), both anti-LFA-1 and anti-ICAM-1 MoAbs (50 micrograms each/mouse/day) were given intraperitoneally after transplantation for the first 4 weeks. In the syngeneic and untreated allogeneic groups, all mice were killed 4 weeks after transplantation. In the treated allogeneic group, eight mice were killed 6 weeks after cessation of the MoAb treatment. At the time the mice were killed, the bowel graft as well as the recipient spleen were taken for histologic analysis and cytotoxic T-lymphocyte (CTL) assay, respectively. Each mouse in the remaining treated five mice was transplanted with BALB/c and C57BL/6 (as third-party) full-thickness skin simultaneously 8 weeks after cessation of the MoAb treatment.

RESULTS

All grafts in the syngeneic group survived with normally developing villi, whereas all grafts in the untreated allogeneic group disappeared. In the treated allogeneic group, all allografts developed normal mucosa without any sign of rejection. Splenocytes from the recipient mice in the untreated allogeneic group showed increased CTL induction against donor-type alloantigen (p < 0.005), compared with that in the syngeneic group. Suppressed CTL induction against donor-type alloantigen was observed in the treated allografted recipient (p < 0.001), whereas CTL induction against third-party alloantigen was intact (p = NS). Third-party skin graft was normally rejected within 10 days, whereas donor-type skin graft was accepted in all mice tested.

CONCLUSIONS

Specific tolerance for fetal bowel allografts could be induced by a relatively short-term treatment with anti-ICAM-1 and anti-LFA-1 MoAbs. This mode of immunointervention could perhaps be applied to humans undergoing small-bowel transplantation.

Intercellular adhesion molecule-1

The intercellular adhesion molecule (ICAM) 1 is an Ig-like cell adhesion molecule expressed by several cell types, including leukocytes and endothelial cells. It can be induced in a cell-specific manner by several cytokines, for example, tumor necrosis factor-alpha, interleukin-1, and interferon-gamma, and inhibited by glucocorticoids. Its ligands are the membrane-bound integrin receptors LFA-1 and Mac-1 on leukocytes, CD43, the soluble molecule fibrinogen, the matrix factor hyaluronan, rhinoviruses, and Plasmodium falciparum malaria-infected erythrocytes. ICAM-1 expression is predominantly transcriptionally regulated. The ICAM-1 promoter contains several enhancer elements, among them a novel kappa B element which mediates effects of 12-O-tetradecanoylphorbol-13-acetate, interleukin-1, lipopolysaccharide, tumor necrosis factor-alpha, and glucocorticoids. Expression regulation is cell specific and depends on the availability of cytokine/hormone receptors, signal transduction pathways, transcription factors, and posttranscriptional modification. ICAM-1 plays a role in inflammatory processes and in the T-cell mediated host defense system. It functions as a costimulatory molecule on antigen-presenting cells to activate MHC class II restricted T-cells, and on other cell types in association with MHC class I to activate cytotoxic T-cells. ICAM-1 on endothelium plays an important role in migration of (activated) leukocytes to sites of inflammation. ICAM-1 is shed by the cell and detected in plasma as sICAM-1. Regulation and significance of sICAM-1 are as yet unclear, but sICAM-1 is increased in many pathological conditions. ICAM-1 may play a pathogenetic role in rhinovirus infections. Derangement of ICAM-1 expression probably contributes to the clinical manifestations of a variety of diseases, predominantly by interfering with normal immune function. Among these are malignancies (e.g., melanoma and lymphomas), many inflammatory disorders (e.g., asthma and autoimmune disorders), atherosclerosis, ischemia, certain neurological disorders, and allogeneic organ transplantation. Interference with ICAM-1 leukocyte interaction using mAbs, soluble ICAM-1, antisense ICAM-1 RNA, and in the case of melanoma mAb-coupled immunotoxin, may offer therapeutic possibilities in the future. Integration of knowledge concerning membrane-bound and soluble ICAM-1 into a single functional system is likely to contribute to elucidating the immunoregulatory function of ICAM-1 and its pathophysiological significance in various disease entities.

Effects of desferrioxamine on human cytomegalovirus replication and expression of HLA antigens and adhesion molecules in human vascular endothelial cells

Desferrioxamine (DFO), commonly used in therapy as a chelator of ferric ion in disorders of iron overload, is a potent inhibitor of human cytomegalovirus (HCMV) replication in cultured fibroblast cells. Moreover, DFO has immunomodulatory activity both in vitro and in vivo. We studied DFO effects on HCMV replication in cultured human endothelial cells and on the expression of several cell surface molecules, which mediate interactions of endothelial cells with other cell types in the immune system. The concentrations of DFO required for 50% reduction in the number of endothelial cells expressing HCMV late antigen, ranged for several HCMV strains from 5.2 to 8.8 microM. DFO concentrations ranging from 5 to 40 microM inhibited cellular DNA synthesis in a dose-dependent manner without any significant effects on the cell viability. DFO at 10 microM concentration suppressed expression of intercellular adhesion molecule-1 (ICAM-1) and endothelial leucocyte adhesion molecule-1 (ELAM-1), while it had no significant effect on the expression of vascular cell adhesion molecule-1 (VCAM-1). Expression of HLA class I and class II was not influenced by DFO treatment. The results showed that DFO is both effective in inhibition of HCMV replication and expression of ICAM-1 and ELAM-1 in endothelial cells, a combination that warrants attention to its potential use to prevent HCMV-induced allograft rejection in transplant recipients.

The role of cellular adhesion molecules in surgery

The purpose of this review is to detail the roles played by the cellular adhesion molecules (CAM) in inflammatory and immunological reactions relevant to surgery. The interactions between leucocytes and endothelial cells which are mediated by CAM are central to the development of ischaemia/reperfusion injury (IRI) as occurs when blood flow is restored after an ischaemic period; for example, following revascularization of replanted digits and microvascular tissue transfers, angioplasty and tourniquet procedures. Cellular adhesion molecules are also important in wound healing and other inflammatory processes. In addition, the immunological response to organ allograft transplantation is mediated by cellular interactions mediated by CAM. This review details the functions and regulation of the various CAM involved in inflammation and allograft rejection and summarizes the results of previous surgical studies in which various techniques have been used to block the interactions mediated by CAM in an attempt to improve surgical outcomes.

Leukocyte CD18 receptors may be a better target than ICAM-1 ligands for reducing histologic evidence of cellular and vascular rejection in the rabbit

Building evidence suggests that blocking the ICAM-1/CD18 interaction may affect the course of graft rejection. Treatment with monoclonal antibody (mAb) to CD18 was compared to antibody to ICAM-1 in a rabbit heterotopic heart transplant model to determine whether blocking the leukocyte receptor for ICAM-1, CD18, was more effective than antibody targeting of the ligand for ICAM-1. Following transplantation, 28 recipient rabbits were randomized to receive either placebo, mAb to CD18, or mAb to ICAM-1 for 7 days until sacrifice. The cellular rejection grade and percentage of arteries with vascular rejection were significantly lower in animals treated with anti-CD18 than with anti-ICAM-1. As assessed by histology, antibody treatment was more effective in reducing both cellular and vascular rejection when directed at the leukocyte receptor CD18 than the ICAM-1 ligand. These findings suggest that other ICAM ligands may play an active role in the immune response and that CD18 may be important for migration of lymphocytes through myocardium.

Hepatic allograft rejection is associated with increased levels of soluble intercellular adhesion molecule-1

Intercellular adhesion molecule-1 (ICAM-1) is an adhesion molecule from the immunoglobulin super family that is recognized to be an important factor in the multistep process of cell transendothelial migration and lymphocyte adhesion during antigen recognition and effector cytolysis, mechanisms known to be involved in the pathogenesis of hepatic allograft rejection. A soluble form of ICAM-1 (sICAM-1) can be shed into the circulation. In this study, we examined the levels of sICAM-1 in hepatic allograft recipients as possible markers of cellular rejection and the presence of cytomegalovirus (CMV) hepatitis. We studied three groups of patients, including eight patients with histologically documented cellular rejection, five patients with histologically documented CMV hepatitis, and a liver transplantation control population. Serum samples were obtained at the following times: baseline (1 to 3 days after transplantation), at time of diagnosis of cellular rejection, and at time of diagnosis of CMV hepatitis and 1 week after treatment of rejection episodes. The levels of sICAM-1 were measured using an established commercial enzyme immunoassay with a sensitivity of 0.3 ng/mL. We found that serum levels of sICAM-1 were significantly increased in liver transplant recipients who were experiencing hepatic allograft rejection but were unchanged in patients with CMV hepatitis or the time-matched liver transplant controls. Serum levels of sICAM-1 decreased significantly after successful treatment of the rejection episode with bolus corticosteroid therapy. We conclude that serum levels of sICAM-1 may be useful in monitoring the occurrence of rejection and the response to antirejection therapy in liver transplant recipients.

Prevention of fetal bowel allograft rejection by combined treatment with anti-ICAM-1 and anti-LFA-1 antibodies

Prevention and treatment of allograft rejection remain the major issues in clinical small bowel transplantation. New strategies for manipulating immune responses using more powerful immunosuppressive agents continue to be evaluated. The fetal small bowel from BALB/c (H-2d) or C3H/He (H-2k) mice was transplanted into the space between the peritoneum and rectus abdominis of adult C3H/He (H-2k) recipient mice. Syngeneic (n = 6) and allogeneic transplant groups were made. In the allogeneic group, the recipient mice were subdivided into three groups, depending on the duration of combined treatment with anti-LFA-1 and anti-ICAM-1 monoclonal antibodies (MAbs): untreated (n = 10), 7-day course (n = 10), and 4-week course (n = 14). A dose of 50 micrograms/mouse/d each of both MAbs was given intraperitoneally, immediately after transplantation and on the consecutive days. All mice were killed 4 weeks after transplantation, and the graft as well as the recipient spleen were taken for histological examination, graft survival ratio, mixed lymphocyte reaction (MLR) assay and cytotoxic T lymphocyte (CTL) assay. All grafts in the syngeneic group survived with normal villi, whereas all grafts in the allogeneic group without treatment disappeared within 4 weeks. All grafts in the allogeneic group with a 7-day course of MAb treatment showed marked disruption of the mucosa with massive cellular infiltration. However, in the allogeneic group treated for 4 weeks, all allografts had adequate growth and demonstrated normal villi with minimal cellular infiltration. Splenocytes from allografted recipient mice without MAb treatment showed markedly increased MLR and CTL activity, compared with the activity seen in the syngeneic MLR and CTL.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac allograft survival in mice deficient in intercellular adhesion molecule-1

BACKGROUND

Intercellular adhesion molecule-1 (ICAM-1, CD54) is a cell adhesion molecule that interacts with the leukocyte beta 2 integrins, lymphocyte function-associated antigen-1, and macrophage antigen-1. ICAM-1 is postulated to play a key role in several cell-cell interactions that are important in allograft rejection, including antigen presentation, transendothelial migration of leukocytes, and leukocyte-medicated myocyte injury.

METHODS AND RESULTS

Mice homozygous for a gene-targeted mutation of ICAM-1 were used in two different cardiac transplant models to further define the role of ICAM-1 in the process of allograft rejection. In the first model, hearts from newborn mice were implanted in the ear pinnae of H-2-incompatible recipients. In the second model, intra-abdominal transplantation by direct vascular anastomosis was performed. Time to rejection was defined by the loss of pulsatile activity assessed by visual inspection in the ear model or by cessation of palpable cardiac impulse in the abdominal model. Allograft survival did not differ significantly between control groups that express normal levels of ICAM-1 and those groups using ICAM-1-deficient mutants as either donors or recipients. Histological examination of rejection of both normal and mutant (ICAM-1-deficient) cardiac allografts revealed similar patterns of infiltration of mononuclear and granulocytic leukocytes and myocyte necrosis. Immunostaining with anti-ICAM-1 antibodies showed ICAM-1-positive infiltrating cells in both mutant (ICAM-1-deficient) and normal allografts, with the graft endothelium negative for ICAM-1 staining in the mutant allografts.

CONCLUSIONS

The absence of surface expression of ICAM-1 in the donor allograft or recipient is insufficient to produce a significant impact on cardiac allograft survival. This study highlights the need to understand more precisely the mechanism of action whereby monoclonal antibodies to ICAM-1 prolong cardiac allograft survival before new therapeutic strategies based on gene transfer technology or small molecule inhibitors are developed. Mutant mice with targeted mutations in cell adhesion molecules provide powerful tools to study the complex role that cell adhesion molecules play in the cellular interactions between donor graft tissue and the recipient that culminate in graft rejection.

Expression of CD11b and ICAM-1 in an in vivo model of transplant arteriosclerosis

Adhesion molecules play a crucial role in transplant rejection in regulating the interaction of inflammatory cells with cells in the vascular wall. In an aortic transplantation model, we have previously analysed the early adhesion process (7.5 min to 24 h) and the impact of cold ischaemia time (1-24 h) upon transplant arteriosclerosis during the first 2 months after transplantation in the rat. The aim of this investigation was to study adhesion molecules in accelerated transplant arteriosclerosis in a rat model by analysing the immunohistochemical expression of CD11b and ICAM-1 up to 2 months and followed by a semiquantitative evaluation and multivariant analysis. Antigen expression of CD11b and ICAM-1 adhesion molecules was stronger in the aortic allografts than in the ischaemia-induced syngeneic aortic grafts in the whole vessel wall. Neither ICAM-1 nor CD11b antigen expression correlated significantly with time periods of ischaemia/reperfusion injury in allogeneic or syngeneic aortic transplants. CD11b and ICAM-1 are induced by allogeneic stimuli in transplanted aortas suggesting a role in the pathogenesis of transplant arteriosclerosis. Our findings have implications for understanding the role of cell adhesion activation in the vascular wall subject to chronic graft rejection.

Binding of lymphocytes to acutely rejecting rat kidney allografts in vitro is guided by events in the graft itself rather than by sensitization of host lymphocytes

Circulating host lymphocytes recognize, bind to, become activated by, and infiltrate engrafted allogeneic tissues. The mechanisms responsible for these early events which lead to acute immunological rejection have not been precisely defined. We have examined sequentially in vitro lymphocyte binding patterns in a kidney transplant model of acute rejection in rats and their relationship to the expression of two representative adhesion molecules, ICAM-1 and LFA-1. The extent of binding of naive, or allosensitized recipient strain LNL or PBL, or donor strain or third party cells to frozen sections of kidney allografts was not significantly different; adherence was dependent upon whether the graft was an allograft or an isograft. The pattern of lymphocyte adherence to various allograft compartments was distinct and varied with time. Within 3 days after transplantation only a few cells had bound to the frozen tissues, preferentially to vascular endothelium. By days 5 and 7, increasing numbers of cells bound primarily to tubules, as did the few cells adhering to isografts. Immunohistologically, ICAM-1 expression increased progressively during acute rejection, first on vascular endothelium, later on tubules. LFA-1+ infiltrating cells peaked more quickly. Lymphocyte binding could be inhibited (approx. 40%) by monoclonal antibodies directed against LFA-1 and ICAM-1. The results indicate that in vitro lymphocyte binding to acutely rejecting kidney transplants is directed by the allogenicity of the graft itself via upregulation of adhesion molecules rather than sensitization of the host cells.

Future of monoclonal antibodies in solid organ transplantation

The ultimate objective of immunosuppressive therapy is to block transplant recipient reactivity to allograft incompatibilities while sparing other responses. Increased clarification of rejection mechanisms has made possible the precise suppression of specific elements of the immune response using murine anti-human monoclonal antibodies. In addition, recombinant DNA technology has made available novel agents including "humanized," bispecific, or toxin-conjugated molecules, which avoid some of the limitations of murine reagents. Using such agents, donor-specific tolerance has been induced in experimental models after a limited course of therapy directed against selected effector cell surface-associated molecules such as CD4, CD25, and CD54. It remains to be determined how such observations can be successfully transferred to the human situation. It seems likely, however, that as new molecular agents are developed, increasingly effective suppression of specific cellular targets will become an essential element of clinical protocols. Such agents may provide long-term immunosuppression with limited periods of immunosuppressive agent administration.

Effect of crossmatching on outcome in organ transplantation

The complement-dependent cytotoxicity (CDC) crossmatch and the flow cytometry crossmatch (FCXM) are both used prospectively in renal transplantation, and their use is under evaluation in other types of major organ transplantation. The FCXM is the more sensitive method and better predicts outcome in second and subsequent renal allografts. Improved survival has unmasked the detrimental effect of a positive crossmatch on outcome in liver transplantation. Because of the urgent need of liver transplant candidates, it is unrealistic to defer transplantation until a crossmatch-negative donor is found; however, additional therapeutic measures may be taken to improve outcome for crossmatch-positive liver recipients. Some reports suggest that prospective crossmatching may improve outcome for sensitized heart recipients, and, additionally, recent studies have demonstrated that HLA compatibility between donor and recipient is an independent variable affecting survival after heart transplantation, prompting a reassessment of the current practice of transplanting hearts without consideration of the HLA match.

Transient immunosuppressive treatment leads to long-term retention of allogeneic myoblasts in hybrid myofibers

Normal and genetically engineered skeletal muscle cells (myoblasts) show promise as drug delivery vehicles and as therapeutic agents for treating muscle degeneration in muscular dystrophies. A limitation is the immune response of the host to the transplanted cells. Allogeneic myoblasts are rapidly rejected unless immunosuppressants are administered. However, continuous immunosuppression is associated with significant toxic side effects. Here we test whether immunosuppressive treatment, administered only transiently after allogeneic myoblast transplantation, allows the long-term survival of the transplanted cells in mice. Two immunosuppressive treatments with different modes of action were used: (a) cyclosporine A (CSA); and (b) monoclonal antibodies to intracellular adhesion molecule-1 and leukocyte function-associated molecule-1. The use of myoblasts genetically engineered to express beta-galactosidase allowed quantitation of the survival of allogeneic myoblasts at different times after cessation of the immunosuppressive treatments. Without host immunosuppression, allogeneic myoblasts were rejected from all host strains tested, although the relative time course differed as expected for low and high responder strains. The allogeneic myoblasts initially fused with host myofibers, but these hybrid cells were later destroyed by the massive immunological response of the host. However, transient immunosuppressive treatment prevented the hybrid myofiber destruction and led to their long-term retention. Even four months after the cessation of treatment, the hybrid myofibers persisted and no inflammatory infiltrate was present in the tissue. Such long-term survival indicates that transient immunosuppression may greatly increase the utility of myoblast transplantation as a therapeutic approach to the treatment of muscle and nonmuscle disease.

Prospects for induction of tolerance in renal transplantation

Immunological tolerance is the ultimate goal of transplantation immunobiology. Current therapies involve nonspecific immunosuppression with concomitant risks for infection, malignancy, and drug-specific side effects. By inducing specific immune unresponsiveness to the graft it should be possible to maintain transplants without the need for chronic drug administration and without the risk of nonspecific immunosuppression. This review highlights recent progress in the understanding of immunological tolerance, with special attention to the long-term prospects for successful induction of tolerance in renal transplant patients.

The importance of E-selectin as a marker for renal transplant rejection

Vascular endothelial cells express membrane bound adhesion molecules which play a direct role in the localization and subsequent movement of leucocytes from the blood into sites of inflammation. E-Selectin is a cytokine induced adhesion molecule, known to be expressed by endothelial cells in inflammatory conditions, which binds to various leucocyte subpopulations. In a prospective study we have investigated the expression and distribution of E-selectin on renal allograft needle biopsies taken from 16 pretransplant kidneys and 119 post-transplant kidneys. Post-transplant biopsies were taken at times of graft dysfunction and at times of normal graft function. Formal histology was also performed and assessed independently. E-Selectin was found predominantly on the intertubular endothelium and on the endothelium of larger vessels. E-Selectin was present, at low intensity, in some pretransplant biopsies and also some post-transplant biopsies which were reported histologically as normal. In post-transplant biopsies taken for dysfunction E-selectin was present in the majority of cases. Expression was strong in biopsies showing acute cellular rejection and this was associated with a CD4 positive cellular infiltrate. Biopsies showing other causes of dysfunction, in particular acute tubular necrosis, also were E-selectin and CD4 positive with lower intensity than those with acute cellular rejection. These results suggest that E-selectin is a good marker for endothelial activation in renal transplant biopsies. Its presence in histologically apparently normal biopsies suggests that its in vivo kinetics may differ from previously reported in vitro kinetics. E-Selectin may be a potential target for therapeutic intervention.

Pharmacological modulation of endothelial cell-associated adhesion molecule expression: implications for future treatment of dermatological diseases

Skin diseases with an inflammatory component, regardless of their etiology, are characterized at some point by the extravasation and subsequent infiltration of leukocytes into the dermal and/or epidermal compartments. This trafficking pattern is determined by a complex series of events whereby the leukocytes interact with cell adhesion molecules (CAM), particularly those induced on endothelial cells following activation with various inflammatory mediators. Vascular CAMs belonging to the selectin family (i.e., P-selectin and E-selectin) are thought to mediate early and reversible events involving leukocyte rolling and margination along the lumenal surface of microvascular cells (post-capillary venules). Certain members of the immunoglobulin supergene family (i.e., VCAM-1 and ICAM-1) regulate later and irreversible steps which lead to firm attachment and subsequent diapedesis of leukocytes. Accumulating evidence suggests that if one blocks the ligand-binding sites between leukocytes and endothelial cells, or inhibits vascular CAM expression, hematopoietic cell extravasation and progressive inflammatory events can be greatly diminished. To identify such inhibitors we developed a cell-based Elisa using the human microvascular cell line HMEC-1. As reported in the present paper, this approach yielded a naturally-occurring, low molecular weight compound which potently inhibits cytokine-induced adhesion molecule expression on cultured endothelial cells, without modulating "house-keeping" proteins.

Xenotransplantation: an examination of the adhesive interactions between human lymphocytes and porcine renal epithelial cells

Specific adhesion molecules stabilize the binding between lymphocytes and antigen bearing cells; this intercellular adhesion is vital to both the affector and effector phases of an immune response. It is not known whether adhesion molecules and their counter-receptors can form the cross-species interactions that will facilitate human T cell recognition of xenogeneic porcine target cells. In this report it is demonstrated that a higher proportion of mitogen-activated than of resting human lymphocytes adhere to cultured porcine renal epithelial cells. Furthermore, antibody blocking experiments demonstrated that at least part of this cell-cell binding is stabilized by the human adhesion molecules LFA-1 (lymphocyte function-associated antigen-1) and the alpha 4-containing integrins. It is possible that this capacity for cross-species adhesion will play a role during the cell-mediated rejection of clinical porcine xenografts.