Vascular addressins are induced on islet vessels during insulitis in nonobese diabetic mice and are involved in lymphoid cell binding to islet endothelium

In the nonobese diabetic (NOD) mouse, lymphocytic and monocytic infiltration of the pancreatic islets leads to beta cell destruction. To investigate the mechanisms by which lymphocytes enter the NOD pancreas, pancreata were immunostained using monoclonal antibodies to a variety of adhesion molecules known to be involved in lymphocyte binding to vascular endothelium, an initial step in the migration of lymphocytes from blood into organized lymphoid and inflamed tissues. These adhesion molecules include: lymphocyte homing receptors involved in tissue-selective binding of lymphocytes to peripheral lymph node (L-selectin) or mucosal lymphoid tissue (LPAM-1, alpha 4 beta 7-integrin) high-endothelial venules (HEV); and HEV ligands peripheral vascular addressin (PNAd) and mucosal vascular addressin (MAdCAM-1). In NOD pancreata, alpha 4 beta 7 is expressed on most infiltrating cells at all stages of insulitis, whereas L-selectin expression is more pronounced on cells in the islets at later stages. During the development of insulitis, MAdCAM-1 and to a lesser extent PNAd became detectable on vascular endothelium adjacent to and within the inflamed islets. The Stamper-Woodruff in vitro assay was used to examine lymphoid cell binding to such vessels. These functional assays show that both the mucosal (MAdCAM-1/alpha 4 beta 7) and the peripheral (PNAd/L-selectin) recognition systems are involved in this binding. Our findings demonstrate that expression of peripheral and mucosal vascular addressins is induced on endothelium in inflamed islets in NOD pancreas, and that these addressins participate in binding lymphoid cells via their homing receptors. This suggests that these adhesion molecules play a role in the pathogenesis of diabetes in these mice by being involved in the migration of lymphocytes from blood into the inflamed pancreas.

The use of granzyme A as a marker of heart transplant rejection in cyclosporine or anti-CD4 monoclonal antibody-treated rats

Granzyme A is a serine protease expressed by populations of human and mouse natural killer cells and activated CD4+ and CD8+ cytotoxic lymphocytes; its expression marks a subset of inflammatory cells in allografts, autoimmune diabetes, and a number of other inflammatory lesions. In order to describe more completely the correlation between granzyme A expression and the presence of in vivo cytolytic effects, we grafted allogeneic rat hearts with vascular anastomoses in a heterotopic location, and treated the hosts with either cyclosporine, anti-CD4 monoclonal antibody (MRC OX38), or no therapy. The grafts were evaluated by palpation for cardiac functions, by immunohistochemistry for CD4/CD8 expression, by hematoxylin-and-eosin staining for inflammatory infiltration, and by in situ hybridization for granzyme A expression. The appearance of granzyme A+ cells in untreated allografts preceded both functional and standard histopathological and immunohistochemical evidence of graft rejection by two days. In donor-recipient combinations where cyclosporine and anti-CD4 treatments allowed indefinite allograft survival, the allografts showed minimal numbers of granzyme A+ cells, whether cellular infiltrates developed or not. The number of granzyme A+ cells present in the cardiac allografts in treated and untreated animals correlated with either current or impending episodes of rejection. The early time course of granzyme A expression suggests that it can be used as an early and reliable marker of graft rejection.

Genetic control of diabetes mellitus

Genetic inheritance predisposing individuals to diabetes mellitus was discussed in this work group. The two forms of the disease, Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) were discussed separately since the pattern of inheritance and genes involved appear to be distinctly different. Within these subtypes there is considerable genetic heterogeneity, and superimposed environmental factors confound the analysis. New technologies that will allow finer molecular analysis, as well as new candidates genes, were presented.

Genetic dissection of T cell receptor V beta gene requirements for spontaneous murine diabetes

It has been demonstrated, in certain autoimmune disease models, that pathogenic T cells express antigen receptors of limited diversity. It has been suggested that the T cells responsible for the pathogenesis of type I diabetes mellitus might similarly demonstrate restricted T cell receptor (TCR) usage. Recently, attempts have been made to identify the V beta subset(s) that initiates and/or perpetuates the antiislet response in a mouse model of spontaneous autoimmune diabetes (non-obese diabetic [NOD] mice). In studies reported here, we have bred NOD mice to a mouse strain that congenitally lacks approximately one-half of the conventional TCR V beta alleles. Included in this deletion are TCR V beta gene products previously implicated as being involved in the pathogenesis of NOD disease. By studying second backcross-intercross animals, we were able to demonstrate that this deletion of TCR V beta gene segments did not prevent the development of insulitis or diabetes.

Transgenic mice for the study of diabetes mellitus

Several recent studies have utilized transgenic technology to explore basic questions in the pathophysiology of diabetes mellitus. The ultimate expression of altered glucose homeostasis is a theme common to them. The experimental models have been diverse, however, and, in some instances, resulted in unexpected biologic effects. Many of the studies have examined the autoimmune etiology of insulin-dependent diabetes mellitus by expressing regulatory molecules of the immune system as transgenes in islet beta cells. The molecules have included products of the major histocompatibility complex (MHC), cytokines, and other cell surface antigens. Ectopic expression of these transgenes resulted in altered immune responses directed against islets, and these transgenic mice now serve as important models to study mechanisms of immunologic tolerance. Transgenic technology is also being used to explore basic aspects of islet beta-cell physiology and insulin metabolism. beta-cell function is disrupted by transgenic beta-cell expression of molecules such as calmodulin and H-ras. Hyperexpression of insulin as a transgene can result in a syndrome resembling features of non-insulin-dependent diabetes.

Anti-CD4 mediates clonal anergy during transplantation tolerance induction

Depletion of CD4+ cells using anti-CD4 monoclonal antibodies leads to allograft tolerance. Here we show that anti-CD4-mediated tolerance to pancreatic islets of Langerhans transplanted from an A/J (IEk) donor to a diabetic C57B1/6 (B6) (IE-) recipient occurs in the absence of clonal deletion of the potentially IE-reactive V beta 11+ T cells. Instead, a state of clonal anergy is induced in both the CD4+V beta 11+ and CD8+V beta 11+ T cell subsets. This clonal anergy can be partially overcome in vitro by the addition of recombinant interleukin 2.

Genetic analysis of diabetes in the nonobese diabetic mouse. I. MHC and T cell receptor beta gene expression

Backcross nonobese diabetic (NOD) ((NOD x SWr)F1 x NOD) mice (108 females and 105 males) were typed for MHC, TCR V beta, and monitored for 350 days for the onset of diabetes. The presence of "antipolar" antibodies in the sera and the occurrence of insulitis was examined in a proportion of these backcross mice. There was no difference in the incidence of diabetes in mice heterozygous for TCR V beta b/a vs those homozygous for TCR V beta b/b. Among the 17 diabetics (all female) detected in this backcross, 14/17 were H-2nod/nod but 3/17 were H-2nod/q. This supports a previous observation suggesting that the MHC-linked diabetogenic gene originally thought to be recessive may rather be dominant but have a low penetrance in the heterozygous state. Antipolar autoantibodies were found in both female and male backcross mice, and were similarly distributed in diabetic and nondiabetic mice. There appeared to be no correlation between the level of these auto-antibodies and development of diabetes. The incidence and severity of insulitis was linked to MHC but no influence of TCR genes on insulitis nor an association between insulitis and antipolar antibodies could be demonstrated in this study. Further analyses of H-2nod/nod intercross mice homozygous for TCR V beta a or TCR V beta b are currently underway.

Genetic analysis of diabetes in the nonobese diabetic mouse. I. MHC and T cell receptor beta gene expression

Backcross nonobese diabetic (NOD) ((NOD x SWr)F1 x NOD) mice (108 females and 105 males) were typed for MHC, TCR V beta, and monitored for 350 days for the onset of diabetes. The presence of "antipolar" antibodies in the sera and the occurrence of insulitis was examined in a proportion of these backcross mice. There was no difference in the incidence of diabetes in mice heterozygous for TCR V beta b/a vs those homozygous for TCR V beta b/b. Among the 17 diabetics (all female) detected in this backcross, 14/17 were H-2nod/nod but 3/17 were H-2nod/q. This supports a previous observation suggesting that the MHC-linked diabetogenic gene originally thought to be recessive may rather be dominant but have a low penetrance in the heterozygous state. Antipolar autoantibodies were found in both female and male backcross mice, and were similarly distributed in diabetic and nondiabetic mice. There appeared to be no correlation between the level of these auto-antibodies and development of diabetes. The incidence and severity of insulitis was linked to MHC but no influence of TCR genes on insulitis nor an association between insulitis and antipolar antibodies could be demonstrated in this study. Further analyses of H-2nod/nod intercross mice homozygous for TCR V beta a or TCR V beta b are currently underway.

Cardiac allograft prolongation in mice treated with combined posttransplantation total-lymphoid irradiation and anti-L3T4 antibody therapy

Neonatal cardiac allograft survival was examined in mice treated with anti-L3T4 antibody, posttransplantation total lymphoid irradiation (TLI) or a combination of both therapies. Independently, both posttransplantation TLI and short-course antibody treatment allowed minimal prolongation. However, synergistic prolongation in graft survival was observed with the combination (synergistic) therapy. Fluorescence-activated cell sorter analysis of peripheral blood lymphocytes from animals treated with combined anti-L3T4 and posttransplantation TLI additionally revealed "synergy" with respect to the degree of peripheral lymphocyte depletion.

Immunotherapy of the nonobese diabetic mouse: treatment with an antibody to T-helper lymphocytes

Spontaneous diabetes mellitus was blocked in nonobese diabetic mice by treatment with a monoclonal antibody against the L3T4 determinant present on the surface of T-helper lymphocytes. Sustained treatment with the monoclonal antibody led to cessation of the lymphocytic infiltration associated with the destruction of the insulin-producing beta cells. Moreover, the mice remained normoglycemic after the antibody therapy was stopped. These studies indicate that immunotherapy with monoclonal antibodies to the lymphocyte subset may not only halt the progression of diabetes, but may lead to long-term reversal of the disease after therapy has ended.

Islet allograft survival after a single course of treatment of recipient with antibody to L3T4

Allografts of pancreatic islets of Langerhans were induced to survive for an indefinite period in diabetic mice if, at the time of engraftment, the mice received a single course of treatment with a monoclonal antibody directed against the L3T4 determinant, a nonpolymorphic cell surface glycoprotein present on the cell surface of the murine T helper-inducer lymphocyte subset. This treatment allowed the survival of islets of Langerhans transplanted across a major histocompatibility barrier without additional immunosuppression. The results demonstrate that the lymphocyte subset defined by the expression of the L3T4 molecules is central to the induction of allograft rejection and provides a model for tolerance induction for organ allograft transplantation.

Inhibition of rat mixed lymphocyte pancreatic islet cultures with anti-Ia immunotoxin

Studies reported here indicate that an anti-Ia immunotoxin can eliminate the allostimulatory subpopulation of cells present within the islets of Langerhans without damaging the hormone-secreting cells. Such studies made use of an in vitro correlate of transplantation rejection, the mixed lymphocyte islet cell (MLIC) reaction. Using the MLIC, it was demonstrated that an anti-Ia immunotoxin removed cells capable of stimulating the MLIC in a dose-dependent fashion without altering the hormone-secreting functions of the remaining cells when challenged with glucose and theophylline. These studies suggest the feasibility of using such anti-Ia immunotoxins in islet allograft transplantation models to circumvent problems inherent in complement-mediated cytotoxicity, a previously documented effective form of inducing islet allotransplantation tolerance.