Long-term reversal of established autoimmunity upon transient blockade of the LFA-1/intercellular adhesion molecule-1 pathway

Islet beta-cells and intercellular adhesion molecule-1 (ICAM-1): Integrating immune responses that influence autoimmunity and graft rejection

Type 1 diabetes (T1D) develops due to autoimmune targeting of the pancreatic islet β-cells. Clinical symptoms arise from reduced insulin in circulation. The molecular events and interactions between discrete immune cell populations, infiltration of such leukocytes into pancreatic and islet tissue, and selective targeting of the islet β-cells during autoimmunity and graft rejection are not entirely understood. One protein central to antigen presentation, priming of immune cells, trafficking of leukocytes, and vital for leukocyte effector function is the intercellular adhesion molecule-1 (ICAM-1). The gene encoding ICAM-1 is transcriptionally regulated and rapidly responsive (i.e., within hours) to pro-inflammatory cytokines. ICAM-1 is a transmembrane protein that can be glycosylated; its presence on the cell surface provides co-stimulatory functions for immune cell activation and stabilization of cell-cell contacts. ICAM-1 interacts with the β2-integrins, CD11a/CD18 (LFA-1) and CD11b/CD18 (Mac-1), which are present on discrete immune cell populations. A whole-body ICAM-1 deletion protects NOD mice from diabetes onset, strongly implicating this protein in autoimmune responses. Since several different cell types express ICAM-1, its biology is fundamentally essential for various physiological and pathological outcomes. Herein, we review the role of ICAM-1 during both autoimmunity and islet graft rejection to understand the mechanism(s) leading to islet β-cell death and dysfunction that results in insufficient circulating quantities of insulin to control glucose homeostasis.

Integrin Regulated Autoimmune Disorders: Understanding the Role of Mechanical Force in Autoimmunity

The pathophysiology of autoimmune disorders is multifactorial, where immune cell migration, adhesion, and lymphocyte activation play crucial roles in its progression. These immune processes are majorly regulated by adhesion molecules at cell–extracellular matrix (ECM) and cell–cell junctions. Integrin, a transmembrane focal adhesion protein, plays an indispensable role in these immune cell mechanisms. Notably, integrin is regulated by mechanical force and exhibit bidirectional force transmission from both the ECM and cytosol, regulating the immune processes. Recently, integrin mechanosensitivity has been reported in different immune cell processes; however, the underlying mechanics of these integrin-mediated mechanical processes in autoimmunity still remains elusive. In this review, we have discussed how integrin-mediated mechanotransduction could be a linchpin factor in the causation and progression of autoimmune disorders. We have provided an insight into how tissue stiffness exhibits a positive correlation with the autoimmune diseases’ prevalence. This provides a plausible connection between mechanical load and autoimmunity. Overall, gaining insight into the role of mechanical force in diverse immune cell processes and their dysregulation during autoimmune disorders will open a new horizon to understand this physiological anomaly.

CD11a/ICAM-1 blockade combined with IL-2 targeting therapy causes a paradoxical acceleration of type 1 diabetes

Enhancement of regulatory T-cell (Treg) function is the goal of many immunotherapies aimed at treating type 1 diabetes (T1D). The use of interleukin (IL)-2 is hindered by its effects on other populations such as effector T cells and NK cells. Combination therapies aimed at suppressing effector T cells while using IL-2 to expand Tregs could be beneficial and have been trialed in T1D patients. We have investigated a combination therapy using IL-2 and αCD11a blocking antibody to simultaneously expand Tregs and suppress the activation and migration of autoreactive T cells. When non-obese diabetic mice were treated with low-dose IL-2/anti-IL-2 complexes (IL-2c) and αCD11a, significant Treg expansion occurred in both the spleen and pancreas. Activation and IFNγ production by islet-specific T cells was robustly suppressed in the periphery following IL-2c/αCD11a treatment. Surprisingly, combination therapy accelerated diabetes onset compared with control treatments. Analysis of IL-2 responsive populations found that combination therapy increased the activation of CD8⁺ T cells and natural killer (NK) cells specifically within the pancreas despite concomitant Treg expansion. Blocking effector T-cell migration with the inhibitor FTY720 together with IL-2c treatment also resulted in intra-pancreatic expansion of effector cell populations. Thus, inhibiting effector T-cell migration into the islets unleashes islet-resident pathogenic effectors in the presence of low doses of exogenous IL-2.

Differentiation and transplantation of functional pancreatic beta cells generated from induced pluripotent stem cells derived from a type 1 diabetes mouse model

The nonobese diabetic (NOD) mouse is a classical animal model for autoimmune type 1 diabetes (T1D), closely mimicking features of human T1D. Thus, the NOD mouse presents an opportunity to test the effectiveness of induced pluripotent stem cells (iPSCs) as a therapeutic modality for T1D. Here, we demonstrate a proof of concept for cellular therapy using NOD mouse-derived iPSCs (NOD-iPSCs). We generated iPSCs from NOD mouse embryonic fibroblasts or NOD mouse pancreas-derived epithelial cells (NPEs), and applied directed differentiation protocols to differentiate the NOD-iPSCs toward functional pancreatic beta cells. Finally, we investigated whether the NPE-iPSC-derived insulin-producing cells could normalize hyperglycemia in transplanted diabetic mice. The NOD-iPSCs showed typical embryonic stem cell-like characteristics such as expression of markers for pluripotency, in vitro differentiation, teratoma formation, and generation of chimeric mice. We developed a method for stepwise differentiation of NOD-iPSCs into insulin-producing cells, and found that NPE-iPSCs differentiate more readily into insulin-producing cells. The differentiated NPE-iPSCs expressed diverse pancreatic beta cell markers and released insulin in response to glucose and KCl stimulation. Transplantation of the differentiated NPE-iPSCs into diabetic mice resulted in kidney engraftment. The engrafted cells responded to glucose by secreting insulin, thereby normalizing blood glucose levels. We propose that NOD-iPSCs will provide a useful tool for investigating genetic susceptibility to autoimmune diseases and generating a cellular interaction model of T1D, paving the way for the potential application of patient-derived iPSCs in autologous beta cell transplantation for treating diabetes.

Effect of soluble ICAM-1 on a Sjögren's syndrome-like phenotype in NOD mice is disease stage dependent

Introduction

Intercellular adhesion molecule-1 (ICAM-1) is involved in migration and co-stimulation of T and B cells. Membrane bound ICAM-1 is over expressed in the salivary glands (SG) of Sjögren's syndrome (SS) patients and has therefore been proposed as a potential therapeutic target. To test the utility of ICAM-1 as a therapeutic target, we used local gene therapy in Non Obese Diabetic (NOD) mice to express soluble (s)ICAM-1 to compete with membrane bound ICAM-1 for binding with its receptor. Therapy was given prior to and just after the influx of immune cells into the SG.

Methods

A recombinant serotype 2 adeno associated virus (rAAV2) encoding ICAM-1/Fc was constructed and its efficacy tested in the female NOD mice after retrograde instillation in SG at eight (early treatment) and ten (late treatment) weeks of age. SG inflammation was evaluated by focus score and immunohistochemical quantification of infiltrating cell types. Serum and SG tissue were analyzed for immunoglobulins (Ig).

Results

Early treatment with ICAM-1/Fc resulted in decreased average number of inflammatory foci without changes in T and B cell composition. In contrast, late treated mice did not show any change in focus scores, but immunohistochemical staining showed an increase in the overall number of CD4+ and CD8+ T cells. Moreover, early treated mice showed decreased IgM within the SGs, whereas late treated mice had increased IgM levels, and on average higher IgG and IgA.

Conclusions

Blocking the ICAM-1/LFA-1 interaction with sICAM-1/Fc may result in worsening of a SS like phenotype when infiltrates have already formed within the SG. As a treatment for human SS, caution should be taken targeting the ICAM-1 axis since most patients are diagnosed when inflammation is clearly present within the SG.

Polymorphisms of the ICAM-1 exon 6 (E469K) are associated with differentiation of colorectal cancer

Background

Genetic factors are thought to play a role in development for colorectal carcinogenesis. ICAM-1 is a polymorphic gene, thus, the present study investigated the relationship between the polymorphisms of ICAM-1 and the susceptibility and phenotypical characteristics of colorectal cancer (CRC).

Methods

The polymorphisms at ICAM-1 exon 4 (G241R) and exon 6 (E469K) were detected by PCR with sequence-specific primers. The relationship between specific genotypes of ICAM-1 and differentiation of CRC was evaluated by the histological grade.

Results

We showed only GG genotype of ICAM-1 individuals in either CRC or normal controls. The KK genotype of ICAM-1 K469E was found more frequently than in the controls (P < 0.05). Patients with well-differentiated CRC displayed the KK more frequently than those of poor differentiation (P < 0.05).

Conclusion

The findings indicate that polymorphisms of G241R are rare in Chinese population and that KK genotype of ICAM-1 K469E is significantly associated with well differentiation of CRC.

Immune depletion with cellular mobilization imparts immunoregulation and reverses autoimmune diabetes in nonobese diabetic mice

OBJECTIVE

The autoimmune destruction of beta-cells in type 1 diabetes results in a loss of insulin production and glucose homeostasis. As such, an immense interest exists for the development of therapies capable of attenuating this destructive process through restoration of proper immune recognition. Therefore, we investigated the ability of the immune-depleting agent antithymocyte globulin (ATG), as well as the mobilization agent granulocyte colony-stimulating factor (GCSF), to reverse overt hyperglycemia in the nonobese diabetic (NOD) mouse model of type 1 diabetes.

RESEARCH DESIGN AND METHODS

Effects of each therapy were tested in pre-diabetic and diabetic female NOD mice using measurements of glycemia, regulatory T-cell (CD4+CD25+Foxp3+) frequency, insulitis, and/or beta-cell area.

RESULTS

Here, we show that combination therapy of murine ATG and GCSF was remarkably effective at reversing new-onset diabetes in NOD mice and more efficacious than either agent alone. This combination also afforded durable reversal from disease (>180 days postonset) in animals having pronounced hyperglycemia (i.e., up to 500 mg/dl). Additionally, glucose control improved over time in mice subject to remission from type 1 diabetes. Mechanistically, this combination therapy resulted in both immunological (increases in CD4-to-CD8 ratios and splenic regulatory T-cell frequencies) and physiological (increase in the pancreatic beta-cell area, attenuation of pancreatic inflammation) benefits.

CONCLUSIONS

In addition to lending further credence to the notion that combination therapies can enhance efficacy in addressing autoimmune disease, these studies also support the concept for utilizing agents designed for other clinical applications as a means to expedite efforts involving therapeutic translation.

Genetic deficiency of Itgb2 or ItgaL prevents autoimmune diabetes through distinctly different mechanisms in NOD/LtJ mice

OBJECTIVE

Insulitis is an important pathological feature of autoimmune diabetes; however, mechanisms governing the recruitment of diabetogenic T-cells into pancreatic islets are poorly understood. Here, we determined the importance of leukocyte integrins beta(2)(Itgb2) and alphaL (ItgaL) in developing insulitis and frank diabetes.

RESEARCH DESIGN AND METHODS

Gene-targeted mutations of either Itgb2 or ItgaL were established on the NOD/LtJ mouse strain. Experiments were performed to measure insulitis and diabetes development. Studies were also performed measuring mutant T-cell adhesion to islet microvascular endothelial cells under hydrodynamic flow conditions. T-cell adhesion molecule profiles and adoptive transfer studies were also performed.

RESULTS

Genetic deficiency of either Itgb2 or ItgaL completely prevented the development of hyperglycemia and frank diabetes in NOD mice. Loss of Itgb2 or ItgaL prevented insulitis with Itgb2 deficiency conferring complete protection. In vitro hydrodynamic flow adhesion studies also showed that loss of Itgb2 completely abrogated T-cell adhesion. However, ItgaL deficiency did not alter NOD T-cell adhesion to or transmigration across islet endothelial cells. Adoptive transfer of ItgaL-deficient splenocytes into NOD/Rag-1 mice did not result in development of diabetes, suggesting a role for ItgaL in NOD/LtJ T-cell activation.

CONCLUSIONS

Together, these data demonstrate that genetic deficiency of Itgb2 or ItgaL confers protection against autoimmune diabetes through distinctly different mechanisms.

The Nore1B/Mst1 complex restrains antigen receptor-induced proliferation of naïve T cells

The Mst1 and Mst2 protein kinases are the mammalian homologs of hippo, a major inhibitor of cell proliferation in Drosophila. Mst1 is most abundant in lymphoid tissues. Mice lacking Mst1 exhibit markedly reduced levels of the Mst1 regulatory protein Nore1B/RAPL in lymphoid cells, whereas Mst2 abundance is unaltered. Mst1-null mice exhibit normal T cell development but low numbers of mature naïve T cells with relatively normal numbers of effector/memory T cells. In vitro, the Mst1-deficient naïve T cells exhibit markedly greater proliferation in response to stimulation of the T cell receptor whereas the proliferative responses of the Mst1-null effector/memory T cell cohort is similar to wild type. Thus, elimination of Mst1 removes a barrier to the activation and proliferative response of naïve T cells. The levels of Mst1 and Nore1B/RAPL in wild-type effector/memory T cells are approximately 10% those seen in wild-type naïve T cells, which may contribute to the enhanced proliferative responses of the former. Freshly isolated Mst1-null T cells exhibit high rates of ongoing apoptosis, a likely basis for their low numbers in vivo; they also exhibit defective clustering of LFA-1, as previously observed for Nore1B/RAPL-deficient T cells. Among known Mst1 substrates, only the phosphorylation of the cell cycle inhibitory proteins MOBKL1A/B is lost entirely in TCR-stimulated, Mst1-deficient T cells. Mst1/2-catalyzed MOBKL1A/B phosphorylation slows proliferation and is therefore a likely contributor to the anti-proliferative action of Mst1 in naïve T cells. The Nore1B/RAPL-Mst1 complex is a negative regulator of naïve T cell proliferation.

LFA-1-mediated T cell costimulation through increased localization of TCR/class II complexes to the central supramolecular activation cluster and exclusion of CD45 from the immunological synapse

T cell activation is associated with a dramatic reorganization of cell surface proteins and associated signaling components into discrete subdomains within the immunological synapse in T cell:APC conjugates. However, the signals that direct the localization of these proteins and the functional significance of this organization have not been established. In this study, we have used wild-type and LFA-1-deficient, DO11.10 TCR transgenic T cells to examine the role of LFA-1 in the formation of the immunological synapse. We found that coengagement of LFA-1 is not required for the formation of the central supramolecular activation cluster (cSMAC) region, but does increase the accumulation of TCR/class II complexes within the cSMAC. In addition, LFA-1 is required for the recruitment and localization of talin into the peripheral supramolecular activation cluster region and exclusion of CD45 from the synapse. The ability of LFA-1 to increase the amount of TCR engaged during synapse formation and segregate the phosphatase, CD45, from the synapse suggests that LFA-1 might enhance proximal TCR signaling. To test this, we combined flow cytometry-based cell adhesion and calcium-signaling assays and found that coengagement of LFA-1 significantly increased the magnitude of the intracellular calcium response following Ag presentation. These data support the idea that in addition to its important role on regulating T cell:APC adhesion, coengagement of LFA-1 can enhance T cell signaling, and suggest that this may be accomplished in part through the organization of proteins within the immunological synapse.

Suppression of established experimental autoimmune uveitis by anti-LFA-1alpha Ab

PURPOSE

To identify costimulatory molecules that are important in the effector phase of experimental autoimmune uveitis (EAU).

METHODS

EAU was induced in C57BL/6 (B6) mice by transfer of activated T cells specific for the interphotoreceptor-binding protein (IRBP) 1-20 peptide. The animals were then treated with and without anti-leukocyte function associated antigen (LFA)-1alpha mAb, at day 0 or 10 (disease onset) after T-cell transfer. Clinical signs of inflammation, ocular histology, and infiltrated inflammatory cells in the eye were compared. The primary and secondary proliferative responses of uveitogenic CD4 and CD8 T cells were tested after treatment with costimulatory blockers in vivo and in vitro. Moreover, the abilities of uveitogenic T cell trafficking and their interaction with retinal astrocytes were examined.

RESULTS

Anti-LFA-1alpha Abs caused significant suppression of disease when administered either at the time of effector uveitogenic T cell transfer or at disease onset. Studies of the mechanisms by which anti-LFA-1alpha Ab inhibits the effector phase of uveitis demonstrated that it blocks multiple pathogenic events of uveitis mediated by IRBP-specific uveitogenic T cells, including the activation of T cells outside and inside the eye and the trafficking of activated autoreactive T cells into the inflammatory site. In addition, Ab treatment selectively suppressed the activation and expansion of pathogenic, but not regulatory, T cells in vivo.

CONCLUSIONS

Anti-LFA-1alpha Abs are potent inhibitors of established autoimmune uveitis and that such treatment may be applicable not only for the prevention, but also the treatment, of T-cell-mediated autoimmune diseases.

Translating the concept of suppressor/regulatory T cells to clinical applications

The in vivo expansion of suppressor/regulatory T cells (Tregs) is a desirable event in autoimmunity and transplantation. Here we summarize the general rules involved in antigen recognition by T cells and describe Tregs and their requirements, discussing different levels of immune intervention.

Decorin overexpression reduces atherosclerosis development in apolipoprotein E-deficient mice

Atherosclerosis results from accumulation of macrophages and extracellular matrix in the arterial wall. Decorin, a small matrix proteoglycan, is able to regulate cell proliferation, migration and growth factors' activity. We investigated the effect of decorin overexpression on atherosclerosis progression in apolipoprotein E-deficient (ApoE(-/-)) mice. Female ApoE(-/-) mice, 10 weeks old (early treatment, n = 20) and 20 weeks old (delayed treatment, n = 20) were administered intravenously with either an adenovirus (2.5 x 10(9) plaque-forming units/mouse) containing human decorin gene (Ad-Dcn) or beta-galactosidase (LacZ), or PBS. Transgenic decorin was mainly expressed in the liver, and was secreted in the plasma up to 4 weeks. Six weeks after treatment, no significant difference in aortic root lesion size was observed between LacZ- and PBS-control groups. In contrast, Ad-Dcn-treated mice showed significantly reduced atherosclerotic lesions as compared to controls in both early and delayed treatment groups (2.9 +/- 1.1% versus 5.5 +/- 0.4%; p = 0.004 and 13.4 +/- 1.3% versus 19.9 +/- 1.41%; p = 0.009, respectively). In parallel, macrophage, gelatinase activity and collagen plaque content were also reduced. Interestingly, plasma triglycerides were reduced and decorin formed complexes with transforming growth factor-beta1 (TGF-beta1) that resulted in reduced circulating free-TGF-beta1. In conclusion, systemic overexpression of decorin reduces inflammation, triglycerides and fibrosis in atherosclerotic plaques of ApoE(-/-) mice resulting in slowing down of disease progression.

Gene therapy for type 1 diabetes

The most intensively studied autoimmune disorder, type 1 diabetes mellitus (DM1), has attracted perhaps the greatest interest for gene-based therapeutic and prophylactic interventions. The final clinical manifestation of this immunologically and genetically complex disease, the absence of insulin, is the major starting point for almost all the gene therapy modalities attempted to date. Insulin replacement by transplantation of islets of Langerhans or surrogate beta cells is the obvious choice, but the allogeneic nature of the transplants activates potent antidonor immunoreactivity necessitating gene and cell-based immunosuppressive strategies as an alternative to the toxic pharmacologic immunosuppressives indicated for classic solid organ transplants. Accumulating knowledge of the cellular mechanisms involved in onset, however, have yielded promising tolerance induction prophylactic approaches using genes and cells. Despite the early successes in a number of animal models, the true test of efficacy in humans remains to be demonstrated.

The inhibition of autoreactive T cell functions by a peptide based on the CDR1 of an anti-DNA autoantibody is via TGF-beta-mediated suppression of LFA-1 and CD44 expression and function

Systemic lupus erythematosus (SLE), which is characterized by the increased production of autoantibodies and defective T cell responses, can be induced in mice by immunization with a human anti-DNA mAb that expresses a major Id, designated 16/6Id. A peptide based on the sequence of the CDR1 of the 16/6Id (human CDR1 (hCDR1)) ameliorated the clinical manifestations of SLE and down-regulated, ex vivo, the 16/6Id-induced T cell proliferation. In this study, we examined the mechanism responsible for the hCDR1-induced modulation of T cell functions related to the pathogenesis of SLE. We found that injection of hCDR1 into BALB/c mice concomitant with their immunization with 16/6Id resulted in a marked elevation of TGF-beta secretion 10 days later. Addition of TGF-beta suppressed the 16/6Id-stimulated T cell proliferation similarly to hCDR1. In addition, we provide evidence that one possible mechanism underlying the hCDR1- and TGFbeta-induced inhibition of T cell proliferation is by down-regulating the expression, and therefore the functions, of a pair of key cell adhesion receptors, LFA-1 (alphaLbeta2) and CD44, which operate as accessory molecules in mediating APC-T cell interactions. Indeed, T cells of mice treated with hCDR1 showed a TGF-beta-induced suppression of adhesion to the LFA-1 and CD44 ligands, hyaluronic acid and ICAM-1, respectively, induced by stromal cell-derived factor-1alpha and PMA. The latter suppression is through the inhibition of ERK phosphorylation. Thus, the down-regulation of SLE-associated responses by hCDR1 treatment may be due to the effect of the up-regulated TGF-beta on the expression and function of T cell adhesion receptors and, consequently, on T cell stimulation, adhesion, and proliferation.

Mechanisms of lymphocyte migration in autoimmune disease

The recruitment of leukocytes to inflamed tissues plays an essential role in combating infection and promoting wound healing. However, in autoimmune diseases such as multiple sclerosis and diabetes, leukocytes enter tissues and contribute to inappropriate inflammatory responses, which cause tissue injury and dysfunction. In diseases of this type, lymphocytes play critical roles in initiating and maintaining these aberrant inflammatory responses. The aim of this review is to examine the mechanisms whereby T-lymphocytes enter tissues in autoimmune diseases and to compare these mechanisms between various organs and diseases. An overview of the mechanisms of leukocyte recruitment and the techniques used to study leukocyte trafficking is provided, focusing on the use of intravital microscopy as a tool to assess the functional microvasculature in vivo. We also discuss the series of tissue homing events which allow naïve lymphocytes to first enter lymph nodes and undergo activation, then subsequently to home to the peripheral organ where their cognate antigen is present. Finally, we examine mechanisms of leukocyte recruitment in diseases such as multiple sclerosis, autoimmune diabetes, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease and asthma.

Systemic Transforming Growth Factor-??1 Gene Therapy Induces Foxp3+ Regulatory Cells, Restores Self-Tolerance, and Facilitates Regeneration Of Beta Cell Function in Overtly Diabetic Nonobese Diabetic Mice

BACKGROUND

Type 1 diabetes results from auto-aggressive T-cell-mediated destruction of beta cells of the pancreas. Recent data suggest that restoration of self-tolerance may facilitate islet-cell regeneration/recovery. In view of the immunoregulatory activity of transforming growth factor (TGF)-beta1, we investigated whether systemic TGF-beta1 gene therapy blocks islet destructive autoimmunity and facilitates regeneration of beta-cell function in overtly diabetic nonobese diabetic (NOD) mice.

METHODS

We used site-directed mutagenesis to create cysteine to serine mutation at sites 224 and 226 and constructed a replication deficient adenovirus (Ad) vector encoding active form of human TGF-beta1 (Ad-hTGF-beta1). Overtly diabetic NOD mice received intravenous injection of Ad-hTGF-beta1. Seven to 14 days after the injection, the mice received transplants with 500 syngeneic islets under the kidney capsule. Islet-graft survival and regeneration of endogenous beta-cell function were examined.

RESULTS

Syngeneic islet grafts failed by day 17 in all untreated mice, whereas Ad-hTGF-beta1 therapy prolonged survival of islet grafts. Islet grafts from treated mice showed well-preserved islets with a peri-islet infiltrate primarily of CD4+ T cells and expression of CD25 and Foxp3. Systemic TGF-beta1 gene therapy was associated with islet regeneration in the native pancreas. Native pancreas of treated mice revealed islets staining strongly for insulin. Similar to what was found in the syngeneic islet graft, there were well-demarcated peri-islet infiltrates that were positive for CD4, TGF-beta1, and Foxp3.

CONCLUSIONS

Our data demonstrate that systemic TGF-beta1 gene therapy blocks islet destructive autoimmunity, facilitates islet regeneration, and cures diabetes in diabetic NOD mice.

Elevated soluble ICAM-1 levels induce immune deficiency and increase adiposity in mice

Elevated soluble intercellular adhesion molecule-1 (sICAM-1) levels have been found in many pathological conditions, including obesity. To determine the effects of elevated sICAM-1 on immune responses and metabolism, we generated a transgenic mouse model overexpressing the extracellular domain of mouse ICAM-1 in the liver. The mice, showing 10-fold higher sICAM-1 levels than wild-type mice, presented elevated neutrophil count. Despite this, after intraperitoneal injection of thioglycollate, neutrophil recruitment into the peritoneal cavity was reduced, and the delayed macrophage recruitment was also affected in the transgenic mice compared with wild-type mice. Inhibition of contact hypersensitivity response in the sICAM-1 transgenic mice was comparable to ICAM-1-deficient mice and characterized by significantly less ear swelling and inflammatory cell infiltration than in wild-type mice. sICAM-1transgenic mice were more susceptible to weight gain on a Western-type diet than wild-type mice, and older animals showed excessive fat accumulation, again reminiscent of ICAM-1-deficient mice. Together, these data indicate that sICAM-1 interferes with ICAM-1-mediated cell-cell interactions, which could produce immune-suppressant effects and alteration of metabolism in persons with high levels of this soluble adhesion receptor.

Alpha L-integrin I domain cyclic peptide antagonist selectively inhibits T cell adhesion to pancreatic islet microvascular endothelium

Insulitis is a hallmark feature of autoimmune diabetes that ultimately results in islet beta-cell destruction. We examined integrin requirements and specific inhibition of integrin structure in T cell and monocyte adhesion to pancreatic islet endothelium. Examination of cell surface integrin expression on WEHI 7.1 T cells revealed prominent expression of beta-, beta(1)-, alpha(L)-integrins, and low expression of alpha(M)-integrins; whereas WEHI 274.1 monocytes showed significant staining for beta(2)-, beta(1)-, alpha(M)-molecules and no expression of alpha(L)-molecules. Unstimulated islet endothelium showed constitutive levels of ICAM-1 counter-ligand expression with minimal VCAM-1 expression; however, TNF-alpha stimulation increased cell surface density of both molecules. TNF-alpha increased T cell and monocyte rolling and adhesion under hydrodynamic flow conditions. Administration of a cyclic peptide competitor for the alpha(L)-integrin I domain binding sites (cyclo1,12-PenITDGEATDSGC) blocked T cell adhesion without inhibiting monocyte adhesion. Examination of T cell rolling revealed that cLAB.L treatment increased the average rolling velocity on activated endothelium and significantly decreased the fraction of T cells rolling at < or =50 microm/s, suggesting that cLAB.L treatment interferes with signal activation events required for the conversion of T cell rolling to firm adhesion. These data demonstrate for the first time that cyclic peptide antagonists against alpha(L)-integrin I domain attenuate T cell recruitment to islet endothelium.

Adhesion molecules as therapeutic targets

This article focuses on the importance of cell-adhesion molecules in the process of allergic inflammation. After reviewing the contribution of different families of adhesion molecules to the cellular recruitment cascade, phenotypic characteristics of leukocyte subtypes are discussed to illustrate how expression of differing patterns of adhesion molecules and their counterligands within tissues influence the type of inflammatory response that occurs. The involvement of adhesion molecules in allergic inflammation in animal models and human studies is described. Examples of specific adhesion-molecule antagonists are provided, and results of their use in human studies of allergic and other inflammatory conditions are discussed.

Effects of streptozotocin on autoimmune diabetes in NOD mice

Non-obese diabetic (NOD) mice develop autoimmunity that destroys their native beta cells causing diabetes. Their autoimmunity will also destroy syngeneic transplanted islets and transfer both autoimmunity and diabetes via spleen cells to non-diabetic mice. In this report, we studied the effects of streptozotocin (STZ) on the autoimmune diabetes in NOD mice. We transplanted NOD.SCID islets into three groups of NOD mice: (1) spontaneously diabetic NOD mice (NOD-sp.); (2) prediabetic NOD mice made diabetic by streptozotocin (NOD-stz); and (3) diabetic NOD mice also treated with streptozotocin (NOD-sp./stz). In the first group, the transplants were rejected within 3 weeks. In the second and third groups, the transplants survived indefinitely. Alloxan, a drug similar to streptozotocin, did not have the same effect as streptozotocin. The ability of streptozotocin to prevent diabetes in young NOD mice was reversed by anti-CD8 antibody treatment but not by anti-CD4 treatment. Streptozotocin also made spleen cells from diabetic NOD mice less effective transferring diabetes. These results indicate that streptozotocin treatment both prevents and reverses the islet destructive autoimmunity in NOD mice. We postulate that the effects of streptozotocin treatment may be mediated in part by regulatory T cells.

Gene- and cell-based therapeutics for type I diabetes mellitus

Type 1 diabetes mellitus, an autoimmune disorder is an attractive candidate for gene and cell-based therapy. From the use of gene-engineered immune cells to induce hyporesponsiveness to autoantigens to islet and beta cell surrogate transplants expressing immunoregulatory genes to provide a local pocket of immune privilege, these strategies have demonstrated proof of concept to the point where translational studies can be initiated. Nonetheless, along with the proof of concept, a number of important issues have been raised by the choice of vector and expression system as well as the point of intervention; prophylactic or therapeutic. An assessment of the current state of the science and potential leads to the conclusion that some strategies are ready for safety trials while others require varying degrees of technical and conceptual refinement.

NKT cell defects in NOD mice suggest therapeutic opportunities

Recent studies have reported that immunoregulatory NKT cells are defective in NOD mice and that treatment of mice with alpha-galactosylceramide that selectively stimulate NKT cells, is anti-diabetogenic. The objective of this study was to document the natural history of changes in NKT cells in various organs in NOD mice in the period up to the time of diabetes onset so that novel intervention therapies could be devised. We found that NKT cell-specific receptor (NKT-TCR) Valpha14Jalpha281 expressions by quantitative (RealTime) RT-PCR in thymus, spleen and liver of NOD male and female mice were low at 1-3 months of life compared to BALB/c and C57BL/6 mice, albeit a transient spike in levels occurred in female NOD livers at 2 months. Female pancreases showed low levels of these transcripts despite their active and destructive insulitis. In contrast, NOD males exhibited high expression of this invariant TCR in pancreas, where their insulitis was less destructive. A survey of NKT-TCR expressions in a battery of congenic, non-diabetes prone NOD strains indicated that this NKT phenotype was quite variable but higher than diabetes prone NOD. Bone marrow transplantation of NOD females from B6.NOD-H2(g7) donors raised their NKT-TCR expressions. Tuberculin administrations in the forms of BCG and CFA in a manner known to protect NOD mice from diabetes both raised NKT-TCR levels, as did the anti-inflammatory PPAR-gamma agonist rosiglitazone. These findings provide exciting therapeutic avenues to be explored in the treatment of human immune mediated type-1 diabetes where there are similar immunoregulatory lesions.

Prolonged islet allograft survival by adenovirus-mediated transfer of sICAM-1/Ig immunoadhesin gene

Administration of monoclonal antibodies directed against the leukocyte function-associated antigen 1 (LFA-1)-intercellular adhesion molecule 1 (ICAM-1) pathway showed that these costimulatory molecules play a key role in allograft rejection. Here, adenoviral gene transfer of an immunoadhesin, sICAM-1/Ig, was used to prolong islet allograft survival in a mouse model, and was compared with anti-LFA-1 antibody administration. A replication-deficient recombinant adenoviral vector encoding a chimeric protein, in which the extracellular domain of ICAM-1 is covalently linked to the C(H)2-C(H)3 domains of an IgG1, was used for gene transfer. C3H murine islets were transplanted under the kidney capsule of streptozotocin-induced diabetic BALB/c mice. Experimental groups underwent adenovirus vector administration either in vivo (intravenous injection) or ex vivo (gene transfer to the graft), and control groups received either an empty vector (Ad.null) or an anti-LFA-1 monoclonal antibody. Graft survival was significantly prolonged by in vivo sICAM-1/Ig gene transfer as compared with both Ad.null and anti-LFA-1 groups, but not by ex vivo gene transfer. Histological examination of the grafts showed the presence of a mononuclear infiltrate within functioning grafts, suggesting that the homing of alloreactive T cells was not altered. In vitro T cell proliferation experiments indicated that sICAM-1/Ig exerted agonist effects on both CD4(+) and CD8(+) T cells.