Evidence for the role of CD8+ cytotoxic T cells in the destruction of pancreatic beta-cells in nonobese diabetic mice

CD8+ islet cell-specific CTL lines and clones were established from lymphocytes infiltrating the pancreatic islets of acutely diabetic nonobese diabetic (NOD) mice from two subcolonies (NOD/Yn and NOD/Lt). CTL from NOD/Yn mice were predominantly cytotoxic against H-2b+ islet cells and to a lesser extent against H-2d+ islet cells. On the other hand, CTL from NOD/Lt mice were cytotoxic against H-2d+ but not against H-2b+ islet cells. Three of four CTL clones derived from NOD/Yn mice were H-2Db restricted, whereas two of two CTL clones derived from NOD/Lt mice were H-2Kd restricted. However, all of the H-2Kd restricted T cell clones expressed the same TCR, regardless of the NOD subcolony from which they were derived, compatible with a restricted repertoire. When two representative CTL clones were transferred into irradiated young NOD mice, neither induced insulitis or diabetes. However, transfer of these clones, together with CD4(+)-rich NOD splenocytes depleted of CD8+ T cells, caused severe insulitis and diabetes. When recipient NOD mice were treated with anti-CD4 mAbs, none of the mice developed insulitis or diabetes. Most of the irradiated NOD mice that received CD8-depleted splenocytes alone did not become diabetic. Through these studies we show that CTL clones can destroy pancreatic beta-cells as final effectors but that these clones require signals from CD4+ T cells to effect beta-cell damage.

Initiation of autoimmune type 1 diabetes and molecular cloning of a gene encoding for islet cell-specific 37kd autoantigen

Insulin-dependent diabetes mellitus (IDDM) is believed to be an autoimmune disease, characterized by lymphocytic infiltration of the islets and the presence of islet cell autoantibodies. Autoimmunity may result from an intrinsically abnormal immune system, primary alterations of the target beta cell or both. However, the initial event that causes the beta cell-specific autoimmunity remains unknown. Our recent experimental results showed that islet grafts from neonatal BB rats remained intact without insulitis when transplanted into the renal subcapsular space of acutely diabetic BB rats. In contrast, islet grafts from adult BB rats (which had been treated with silica for the prevention of insulitis) revealed severe insulitis and were rapidly destroyed. These results suggest that the delayed expression of a beta cell-specific autoantigen may result in the initiation of beta cell-specific autoimmunity. The islet cell-specific 37 kd autoantigen is not expressed early in the life of BB rats, but is expressed at around 30 days of age. This islet-specific autoantigen might be recognized and attacked by the immune effectors. In contrast, nondiabetic Wistar Furth rats express the autoantigen from birth.

Prevention of autoimmune type I diabetes by CD4+ suppressor T cells in superantigen-treated non-obese diabetic mice

The development of autoimmune type I diabetes in the NOD mouse appears to be controlled by both genetic and environmental factors. This investigation was initiated to determine whether exogenous superantigens, as environmental factors, can influence the development of diabetes. Several staphylococcal enterotoxins (SE) (SEA, SEC1, SEC2, or SEC3), which are known superantigens, were injected i.v. into female NOD mice at 4 and 10 wk of age. At 32 wk of age, the incidence of diabetes in the SE-treated mice ranged from 6 to 12.5%; this was significantly lower than that of mice treated with PBS--64%. There was no significant difference in effectiveness among the various SE used. SE induced a modest decrease in T lymphocytes bearing specific V beta TCR 2 wk after injection, but this effect did not persist past 4 wk. To elucidate the mechanism of the SE effect, suppressor activity in SE-treated mice was evaluated. Splenocytes from SE-treated mice inhibited the transfer of diabetes by splenocytes from acutely diabetic NOD mice when injected into irradiated young NOD mice; only 10% became diabetic. In contrast, 83% of the mice receiving splenocytes from PBS-treated control mice became diabetic. Suppressor activity of splenocytes from SE-treated mice was diminished by the depletion of CD4+ T cells, but not by the depletion of CD8+ T cells, indicating that the suppressor cells belonged to the CD4+ T class of lymphocytes. On the basis of these observations, we conclude that exogenous superantigens activate CD4+ suppressor T cells, leading to the prevention of autoimmune type I diabetes in NOD mice.

Prevention of autoimmune type I diabetes by CD4+ suppressor T cells in superantigen-treated non-obese diabetic mice

The development of autoimmune type I diabetes in the NOD mouse appears to be controlled by both genetic and environmental factors. This investigation was initiated to determine whether exogenous superantigens, as environmental factors, can influence the development of diabetes. Several staphylococcal enterotoxins (SE) (SEA, SEC1, SEC2, or SEC3), which are known superantigens, were injected i.v. into female NOD mice at 4 and 10 wk of age. At 32 wk of age, the incidence of diabetes in the SE-treated mice ranged from 6 to 12.5%; this was significantly lower than that of mice treated with PBS--64%. There was no significant difference in effectiveness among the various SE used. SE induced a modest decrease in T lymphocytes bearing specific V beta TCR 2 wk after injection, but this effect did not persist past 4 wk. To elucidate the mechanism of the SE effect, suppressor activity in SE-treated mice was evaluated. Splenocytes from SE-treated mice inhibited the transfer of diabetes by splenocytes from acutely diabetic NOD mice when injected into irradiated young NOD mice; only 10% became diabetic. In contrast, 83% of the mice receiving splenocytes from PBS-treated control mice became diabetic. Suppressor activity of splenocytes from SE-treated mice was diminished by the depletion of CD4+ T cells, but not by the depletion of CD8+ T cells, indicating that the suppressor cells belonged to the CD4+ T class of lymphocytes. On the basis of these observations, we conclude that exogenous superantigens activate CD4+ suppressor T cells, leading to the prevention of autoimmune type I diabetes in NOD mice.

Development of a recombinant RNA technique for the construction of chimeric RNA with a long poly(C) tract

The murine cardioviruses and bovine aphthoviruses are distinguished from other (+) strand RNA viruses by their long poly(C) tract in the 5'-noncoding region. The presence of this poly(C) tract has long hampered the construction of full-length cDNA with the complete poly(C) tract, because long poly(dC-dG) homopolymer-containing plasmids are difficult to amplify in bacterial systems. To overcome this problem, we constructed a chimeric RNA by joining the poly(C) region of the viral RNA to the 5'-truncated RNA transcript of the encephalomyocarditis (EMC) virus cDNA. The non-chimeric, recombinant EMC virus with a short poly(C) tract produces recombinant progeny virus, but this is not pathogenic in vivo. On the other hand, the EMC viral RNA chimera with the complete poly(C) tract produces recombinant progeny virus that is pathogenic in vivo. This method of viral RNA construction will be invaluable for functional studies of other cardioviruses and aphthoviruses, as well as for recombinant RNA manipulations.

A genetically determined host factor controlling susceptibility to encephalomyocarditis virus-induced diabetes in mice

Levels of insulin mRNA in pancreata from SJL/J male mice susceptible to encephalomyocarditis (EMC)-D virus-induced diabetes started to decrease rapidly 24 h after injection with EMC-D virus and only a trace remained 72 h after injection. In contrast, insulin mRNA in pancreata from C57BL/6J male mice resistant to EMC-D virus-induced diabetes did not show any significant changes 0 to 96 h after injection. EMC-D viral RNA in pancreata from SJL/J mice started to increase rapidly 24 h after injection, reached its peak at 48 h and then decreased gradually. In contrast, EMC-D viral RNA in pancreata from C57BL/6J mice was undetectable except for the 24 and 48 h points after injection. EMC-D virus could bind readily to freshly isolated beta cells from SJL/J mice but scarcely bound to beta cells from C57BL/6J mice. In contrast, there was no significant difference between SJL/J and C57BL/6J mice in binding of EMC-D virus to their cultured beta cells. The rate of EMC-D viral attachment to beta cells from C57BL/6J mice increased significantly during the first 24 h culture period and reached the same rate of attachment as that seen for beta cells from SJL/J mice. This suggests that viral receptors on the beta cells derived from strains of mice resistant to EMC virus-induced diabetes are not expressed in vivo, but are expressed during cell culture, rendering the beta cells susceptible to EMC viral infection. On the basis of our previous and present observations, we conclude that a genetic factor controlling susceptibility to EMC-D virus-induced diabetes may operate by modulating the expression of viral receptors on the beta cells.

Determination of diabetogenicity attributable to a single amino acid, Ala776, on the polyprotein of encephalomyocarditis virus

The best experimental evidence indicating that viruses have an etiological role in the pathogenesis of diabetes comes from studies of mice infected with EMC virus. For this study we generated mutant viruses from stocks of diabetogenic EMC-D and nondiabetogenic EMC-B viruses by serial passages of the viruses in L-cell cultures at high MOI. The genomic sequence information and the biological activities of three different plaque-purified diabetogenic variants of EMC virus (EMC-D, EMC-D1/6A, EMC-D2/4) and six different plaque-purified nondiabetogenic variants (EMC-B, EMC-BS, EMC-B1/G, EMC-DV1, EMC-D4/1B, EMC-D3/1) revealed that only one amino acid, Ala (776th amino acid on the polyprotein), is critical for the diabetogenicity of EMC virus. The G base at the nucleotide position 3155 (Ala[GCC]776 in the polyprotein) is unique to all diabetogenic variants, whereas the A base at the same position (Thr[ACC]776 in the polyprotein) is identical to all nondiabetogenic variants. A single-point mutation (G to A; Ala to Thr) results in the conversion of the diabetogenic variant into a nondiabetogenic variant of EMC virus. On the basis of these observations, we conclude that a single amino acid, Ala776, on the polyprotein of EMC virus appears responsible for the inducement of diabetes in susceptible mice. Conversion of Ala776 into Thr776 on the polyprotein by a point mutation, G to A at the nucleotide position 3155, results in the loss of diabetogenicity.

Induction and prevention of type 1 diabetes mellitus by viruses

Genetic factors and environmental factors are thought to be involved in the pathogenesis of insulin-dependent diabetes mellitus Type 1. Viruses, as one environmental factor, may act as primary injurious agents to beta cells or as triggering agents for autoimmunity. Some viruses such as EMC-D and Coxsackie B4 can induce Type 1 diabetes by infecting and destroying beta cells in genetically susceptible mice. In addition, certain species of monkey, such as Patas, show elevated blood glucose levels and depressed insulin secretion after infection with Coxsackie B4 virus. An occasional case of Type 1 diabetes mellitus appears to be associated with the infection of beta cells with Coxsackie B viruses. In addition, Coxsackie B4 virus may also generate viral antigen-specific cytotoxic T cells which may cross-react with a beta cell-specific autoantigen leading to autoimmune Type 1 diabetes. In the case of viral triggering of autoimmune Type 1 diabetes, certain viruses (eg, retrovirus in NOD mice and rubella virus in hamsters and humans) may alter a normally existing beta cell antigen into an immunogenic form or might induce a new antigen, leading to beta cell-specific autoimmune insulin dependent diabetes mellitus. In addition, other viruses (eg, Kilham's rat virus in DR-BB rats) could generate antigen-specific T effector cells which may cross-react with a beta cell-specific autoantigen. In contrast to the induction of diabetes, viruses can prevent the development of diabetes. Inoculation of DP-BB or NOD mice with lymphocytic choriomeningitis virus reduced the incidence of diabetes or prevented the disease by disordering particular lymphocyte subsets.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on autoimmunity for T-cell-mediated beta-cell destruction. Distinct difference in beta-cell destruction between CD4+ and CD8+ T-cell clones derived from lymphocytes infiltrating the islets of NOD mice

Six CD4+ and three CD8+ islet-reactive T-cell clones were established from lymphocytes infiltrating the pancreatic islets of NOD mice. Two of six CD4+ T-cell clones responded to NOD islet cells only, not to spleen cells. The remaining four clones responded to both islet cells and spleen cells from NOD mice, but not to cells from other strains of mice, including SJL, C3H, C57BL/6, and DBA/2 mice. None of the CD4+ T-cell clones had a cytotoxic effect on the cultured islet cells. On the other hand, all of the CD8+ T-cell clones showed both a proliferative response and a cytotoxic effect on the islet cells, with the restriction of MHC class I H-2Db. Electron microscopic studies revealed that islet-specific CD4+ T-cells attached closely to islet cells but did not destroy them. In contrast, CD8+ T-cell clones showed pseudopodialike protrusions into beta-cells, but not alpha- or delta-cells, leading to selective destruction of beta-cells. CD8+ CTLs could not be isolated from islets of NOD mice less than 10 wk of age, even if the islets showed lymphocytic infiltration, whereas CD4+ T-cells could be isolated from islets of these younger NOD mice. On the basis of these observations, we concluded that CD4+ and CD8+ T-cells interact differently with beta-cells at different stages in T-cell--mediated beta-cell destruction. CD4+ T-cells may secrete cytokines, which in turn activate effector cell populations, whereas CD8+ T-cells may act as a final effector directly involved in beta-cell destruction.

Immunogenetic and nutritional profile in insulin-using youth-onset diabetics in Korea

There are few reports on the genetic, immunological and nutritional characteristics of insulin-using youth-onset diabetes mellitus, insulin-dependent diabetes mellitus (IDDM) and malnutrition-related diabetes mellitus (MRDM) in Korea. Among 1266 hospitalized Korean diabetics, 29 (2.3%) were IDDM and 84 (6.6%) were MRDM. A diabetes history of first-relatives (28.6%) was more frequently found in the MRDM group than in the IDDM (14.8) and non-insulin-dependent diabetes mellitus (NIDDM) (19.0%) groups. HLA-DR4 was more common among IDDM (54.2%) and MRDM (52.4%) patients than controls (26.3%), and HLA-DR3 was more common among only IDDM patients (29.2%) than controls (10.9%). Conventional islet-cell antibodies were detected in 8 of 15 IDDM patients tested (53.3%) and in 11 of 22 MRDM patients (50.0%). MRDM patients had higher serum basal (1.02 +/- 0.51 ng/ml) and peak (1.44 +/- 0.76 ng/ml) C-peptide concentrations than IDDM patients, but lower concentrations than NIDDM patients. Before the onset of diabetes, the calorie intake of 21 MRDM patients assessed was 63.1% of the daily requirement and the intake of carbohydrate, protein and fat was 71.7%, 55.9% and 39.8%, respectively. In summary, our data suggest that IDDM in Korea is associated with HLA-DR3 or HLA-DR4, indicating a risk for IDDM in Western societies; furthermore, MRDM has a history of undernutrition at the preonset period and is also associated with HLA-DR4. It might be also concluded that MRDM in Korea is another expression of IDDM caused by the shortage of some nutrients for the structural and/or functional maintenance of pancreatic beta-cells.

Induction of an organ-specific autoimmune disease, lymphocytic hypophysitis, in hamsters by recombinant rubella virus glycoprotein and prevention of disease by neonatal thymectomy

Glycosylated, membrane-associated E1 (58-kDa) and E2 (47- to 49-kDa) rubella virus proteins and unglycosylated nucleoprotein C (33 kDa), from separately expressed vaccinia virus recombinants, were injected into golden Syrian hamsters. Rubella virus E1 and E2 glycoproteins consistently induced an organ-specific autoimmune disease, autoimmune lymphocytic hypophysitis, which was evidenced by the induction of autoantibodies against pituitary cells and by lymphocytic infiltration of the pituitary. Neonatal thymectomy prevented the disease. In contrast, rubella virus nucleoprotein C did not induce either autoantibodies against pituitary cells or lymphocytic infiltration of the pituitary. This finding raises the possibility that virus-specific protein itself can induce an organ-specific autoimmune disease in certain circumstances.

Direct involvement of macrophages in destruction of beta-cells leading to development of diabetes in virus-infected mice

A single administration of complete Freund's adjuvant (CFA), type 1 carrageenan (Car), or silica 7, 2, and 2 days, respectively, before infection with a low dose (1 x 10(2) plaque-forming units/mouse) of encephalomyocarditis D (EMC-D) virus resulted in a significant increase in the incidence of diabetes in SJL/J mice (100%) compared with untreated EMC-D virus-infected mice (40%). Peritoneal macrophages were isolated from uninfected SJL/J mice, which had been treated once with silica, and transferred into SJL/J mice 2 days before low-dose EMC-D infection. Approximately 90% of the mice became diabetic, whereas 30% of mice that received virus alone became diabetic. The depletion of macrophages by treatment with the combined anti-Mac-1 and anti-Mac-2 monoclonal antibodies after a single administration of CFA, Car, or silica resulted in almost complete prevention of beta-cell destruction in EMC-D virus-infected mice. Furthermore, none of the mice in which macrophages were depleted by long-term treatment with silica and 10% of the mice treated with Car before virus infection became diabetic. On the basis of these observations, we conclude that macrophages are directly involved in the destruction of beta-cells, leading to the development of clinical diabetes in EMC-D virus-infected mice.

Role of viruses in the pathogenesis of IDDM

Insulin-dependent diabetes mellitus (IDDM), also known as type I diabetes, results from the destruction of pancreatic beta cells. During the past few decades, genetic factors, autoimmunity and viral infections have been extensively studied as the possible cause of beta cell destruction. The evidence for virus-induced diabetes comes largely from experiments in animals, but several studies in humans also point to viruses as a trigger of this disease in some cases. There are at least two possible mechanisms for the involvement of viruses in the pathogenesis of IDDM: (a) cytolytic infection of beta cells may result in destruction of the cells without the induction of autoimmunity, or may be a final insult leading to the clinical onset of diabetes in individuals with an already decreased beta cell mass resulting from an autoimmune process; and (b) persistent viral infection (e.g. retrovirus, rubella virus, cytomegalovirus) may result in the triggering of autoimmune IDDM in certain circumstances. Regarding the latter possibility, viruses may insert, expose, or alter antigens in the plasma membrane of the beta cell, which may initiate autoimmunity leading to the destruction of the cells.

Studies on autoimmunity for initiation of beta-cell destruction. VIII. Pancreatic beta-cell dependent autoantibody to a 38 kilodalton protein precedes the clinical onset of diabetes in BB rats

Autoantibody to a rat islet cell-protein of 38 kilodalton was detectable at around 30 days of age in the sera of diabetes-prone Biobreeding (DP-BB) rats by both immunoprecipitation and differential Western blotting methods. Anti-38 kilodalton islet cell autoantibody was not, however, observed in the sera from 5- to 20-day-old DP-BB rats. Over 90% of DP-BB rats in which the antibody was detected, eventually developed Type 1 (insulin-dependent) diabetes mellitus. The antibody disappeared within 2 weeks after diabetes onset. However, it was preserved in the sera of DP-BB rats which had been treated with silica to prevent insulitis. The anti-38 kilodalton islet cell autoantibody was not detected in sera from control Wistar Furth (WF) rats. The autoantibody also cross-reacted with a rat insulinoma (RINm5F) cell protein of 38 kilodalton, but did not react with protein from mouse fibroblast (L-929 cells), rat pituitary cells (GH3 cells), or normal rat lymphocytes. The production of the autoantibody appears to be pancreatic Beta-cell dependent, since the autoantibody disappears after almost complete depletion of Beta cells, but is consistently present as long as Beta cells remain. Identification of the Beta-cell dependent anti-38 kilodalton islet cell autoantibody, which cross-reacts with a rat insulinoma cell protein of 38 kilodalton and precedes the onset of Type 1 diabetes in BB rats, will be invaluable for study of the molecular nature of a target islet cell autoantigen associated with the induction of autoimmunity in DP-BB rats.

Studies on autoimmunity for initiation of beta-cell destruction. VII. Evidence for antigenic changes on beta-cells leading to autoimmune destruction of beta-cells in BB rats

The diabetic syndrome in BioBreeding (BB) rats is believed to result from the destruction of beta-cells by autoimmune responses. However, the initial events that cause the autoimmune destruction of beta-cells remain largely unknown. This investigation was initiated to see whether there are any antigenic changes on the beta-cells from neonatal to adult BB rats that may lead to the autoimmune destruction of beta-cells. Pancreatic grafts from neonatal BB rats remained largely intact without insulitis when transplanted into the renal subcapsular space of acutely diabetic BB rats. Similarly transplanted islet grafts from neonatal BB rats were also not subject to autoimmune destruction. In contrast, islet grafts obtained from adult BB rats, which had been treated with silica to prevent insulitis, were rapidly destroyed in diabetic recipients. These results indicate that beta-cells from neonatal BB rats are different from beta-cells from adult BB rats, at least regarding their recognition by immunologic effectors. Considering our observations and previous information on the initial role of macrophages/dendritic cells in the development of insulitis in BB rats, we suggest that beta-cell-specific antigenic changes that precede insulitis may result in the autoimmune destruction of beta-cells in BB rats.

Role of macrophages in the pathogenesis of encephalomyocarditis virus-induced diabetes in mice

Pancreatic islets from SJL/J mice infected with the D variant of encephalomyocarditis virus (EMC-D virus) showed lymphocytic infiltration with moderate to severe destruction of beta cells. Immunohistochemical staining of the islet sections with several monoclonal antibodies, anti-Mac-1, anti-Mac-2, and F4/80 for macrophages, anti-L3T4 for helper/inducer T cells, and anti-Lyt2 for cytotoxic/suppressor T cells revealed that the major population of infiltrating cells at the early stage of viral infection was Mac-2-positive macrophages. In contrast, macrophages detected by anti-Mac-1 and F4/80 monoclonal antibodies were not found at the early stage of viral infection but were found at intermediate and late stages of viral infection. Helper/inducer T cells and cytotoxic/suppressor T cells also infiltrated the islets at intermediate and late stages of viral infection. Short-term treatment of mice with silica prior to viral infection resulted in an enhancement of beta-cell destruction, leading to the development of diabetes. In contrast, long-term treatment of mice with silica resulted in complete prevention of diabetes caused by a low dose of viral infection and a significant decrease in the incidence of diabetes caused by an intermediate or high dose of viral infection. Furthermore, depletion of macrophages by a specific monoclonal antibody (anti-Mac-2) resulted in a much greater decrease in the incidence of diabetes caused by an intermediate dose of viral infection. However, suppression of helper/inducer T cells and cytotoxic/suppressor T cells, by anti-L3T4 and anti-Lyt2 antibodies, respectively, did not alter the incidence of diabetes. On the basis of these data, it is concluded that macrophages, particularly Mac-2-positive macrophages, play a crucial role in the process of pancreatic beta-cell destruction at the early stage of encephalomyocarditis D virus infection in SJL/J mice.

Predisposing effect of anti-beta cell autoimmune process in NOD mice on the induction of diabetes by environmental insults

In NOD mice. 50-70% of females and 10-20% of males develop diabetes, although almost all the animals show insulitis. To see if environmental insults could induce diabetes in subjects with pre-clinical anti-Beta cell autoimmunity, non-diabetic NOD mice were selected and injected with a sub-diabetogenic dose of streptozotocin at 6 or 20 weeks of age. The streptozotocin failed to induce diabetes in 16 male and 16 female NOD mice within 4 weeks when they were injected at the age of 6 weeks. In contrast, 6 of 16 male and 10 of 16 female NOD mice developed diabetes within 4 weeks when they were injected at the age of 20 weeks. In untreated age-matched control NOD mice, none of the male and only 2 of 16 female mice became diabetic during the same 4 week period. On histologic examination, the degree of insulitis in streptozotocin-treated NOD mice (at the age of 24 weeks) was not significantly different from that of untreated control NOD mice. However, the streptozotocin-treated animals showed significantly lower pancreatic insulin content than the control mice. These results show that an anti-Beta cell autoimmune process in NOD mice has a predisposing effect on the induction of diabetes by a sub-diabetogenic dose of streptozotocin, and suggest that the precipitation of clinical diabetes by some environmental insults in subjects with pre-existing pre-clinical autoimmune Beta-cell destruction may be one mechanism of disease presentation in human Type 1 (insulin-dependent) diabetes.

Studies on autoimmunity for initiation of beta-cell destruction. VI. Macrophages essential for development of beta-cell-specific cytotoxic effectors and insulitis in NOD mice

NOD mice were treated with silica (which is selectively toxic to macrophages) from 4 or 20.5 wk of age. Syngeneic neonatal pancreases were transplanted into the renal subcapsular space of the NOD mice at 21 wk of age. Silica treatment was continued until 24 wk of age, and then the mice were killed for examination of islet morphology. Neither the islets in transplanted pancreases nor the host pancreatic islets from the early long-term silica-treated animals revealed insulitis. In contrast, most of the islets in transplanted pancreases from the late short-term silica-treated animals showed severe insulitis and beta-cell necrosis, as did the host islets. A further experiment was performed to compare the effect of late short-term silica treatment with that of anti-L3T4-antibody treatment of the same time and duration. In contrast to the late short-term silica-treated animals, the transplanted pancreases in the anti-L3T4-antibody-treated animals revealed intact islets, although most of the host islets showed insulitis. The control group, which received no treatment but did receive neonatal pancreases, revealed severe insulitis and beta-cell necrosis of both transplanted and host islets. These results suggest that early macrophage depletion can abolish the development of beta-cell-specific immunologic effectors but that late macrophage depletion, after the development of insulitis, does not affect the destruction of beta-cells by preexisting effectors other than macrophages. We conclude that macrophages are essential for the development of beta-cell-specific cytotoxic effectors in the initial phase of insulitis in NOD mice.

Human pancreatic islet cell specific 38 kilodalton autoantigen identified by cytomegalovirus-induced monoclonal islet cell autoantibody

Our previous finding that about 15% of newly diagnosed patients with Type 1 (insulin-dependent) diabetes mellitus had human cytomegalovirus genome in their lymphocytes and islet cell autoantibodies in their sera, suggests that autoimmune Type 1 diabetes is associated with persistent cytomegalovirus infection under certain circumstances. This investigation was initiated to see if cytomegalovirus can induce islet cell autoantibodies and if the autoantibodies react with any specific islet protein(s). Monoclonal antibodies were generated after immunizing Balb/c mice with human cytomegalovirus. When these monoclonal antibodies were tested for the presence of islet cell antibodies were tested for the presence of islet cell antibodies, one (MCMVA-51) of 13 monoclonal antibodies reacted strongly with the islets. The titer of islet cell antibodies was 1:2000. When this monoclonal antibody was reacted with the proteins from the solubilized fraction of human pancreatic islets using the western immunoblotting technique, a band with a molecular weight of 38 kilodalton was detected. The 38 kilodalton band was not observed when the monoclonal antibody was reacted with the proteins prepared from pancreatic islet tissues of rats and mice or from other human organs including stomach, liver, spleen and brain, indicating that the 38 kilodalton protein is human islet cell-specific. It is concluded that human cytomegalovirus can induce islet cell antibodies that react with a 38 kilodalton human islet cell protein and that this protein component may represent islet cell-specific target antigens associated with persistent cytomegalovirus infection.

Studies on autoimmunity for initiation of beta-cell destruction. V. Decrease of macrophage-dependent T lymphocytes and natural killer cytotoxicity in silica-treated BB rats

Administration of silica, which is selectively toxic to macrophages, to young BB rats resulted in the prevention of insulitis and diabetes. However, the mechanism leading to the prevention of an autoimmune process in silica-treated BB rats is not known. This study was undertaken to investigate the mechanism involved in prevention of insulitis and diabetes. Neonates of diabetes-prone BB (DPBB) rats injected with concanavalin A (ConA)-activated spleen cells from silica-treated DPBB (STDPBB) rats did not develop insulitis or diabetes, whereas DPBB neonates injected with ConA-activated spleen cells from the untreated DPBB rats developed both insulitis and diabetes. Not only was there a decrease of natural killer (NK) cell activity in splenocytes from STDPBB rats, but there was also a significant reduction in the number of immunocytes such as T lymphocytes (helper/inducer and cytotoxic/suppressor) and NK cells. The number of macrophages in both spleen and peripheral blood was significantly decreased in STDP rats compared with untreated DP rats. In contrast to the changes in T lymphocytes and NK cell activity, there was no change in target beta-cells in STDPBB rats with regard to the susceptibility to adoptive transfer of insulitis. It is concluded that the prevention of insulitis and diabetes in STDPBB rats is due to a decrease in macrophage-dependent T lymphocytes and NK cell cytotoxicity.

Two amino acids, Phe 16 and Ala 776, on the polyprotein are most likely to be responsible for the diabetogenicity of encephalomyocarditis virus

The diabetogenic D variant of encephalomyocarditis virus (EMC-D) was previously shown to differ from the non-diabetogenic B variant (EMC-B) by 14 nucleotides out of 7829 bases. Similar approaches with a new nondiabetogenic variant, EMC-DV1, obtained by plaque purification of the EMC-D variant stock pool, enabled us to narrow down further the possible genomic area responsible for the diabetogenicity of EMC virus. EMC-DV1 does not induce interferon in vitro, differing from the highly interferon-inducing EMC-B. The complete nucleotide sequence of EMC-DV1 was determined by RNA-dependent DNA sequencing and cDNA sequencing. The genomic size and organization of EMC-DV1 are similar to those of EMC-D and EMC-B, with a long open reading frame encoding a polyprotein of 2292 amino acids. Comparative analyses of sequence information as well as biological activities of EMC-DV1 with EMC-D and EMC-B suggest that (i) the diabetogenicity is apparently distinct from the ability to induce interferon, which is probably due to the single U base insertion at position 765 in EMC-B, and (ii) the diabetogenicity of EMC virus is most probably controlled by one or both of two amino acids, Phe 16 (on the leader peptide) and Ala 776 (152nd amino acid on the VP1) on the polyprotein.

A cytotoxic monoclonal autoantibody from the BB rat which binds an islet cell surface protein

The BB rat provides an excellent animal model for type 1 (insulin-dependent) diabetes mellitus. Cytotoxic autoantibodies against pancreatic beta cells have been found in the sera of both patients with type 1 (insulin-dependent) diabetes and BB rats. These antibodies have been implicated in the pathogenesis of the disease. In this study, a monoclonal autoantibody, designated KT1, has been developed by the fusion of spleen cells from a BB rat and a mouse myeloma cell line. KT1 was found to be of the immunoglobulin M isotype and reacted specifically with islet cells. In microcytotoxicity assays KT1 was shown to mediate complement-dependent lysis of approximately 30% of a rat insulinoma cell line and 25% of rat pancreatic islet cells in culture. It did not cause lysis of the other cell lines tested. KT1 has been demonstrated, by indirect immunofluorescence, to bind specifically to a cell surface antigen on live and acetone-fixed islet cell cultures from Wistar rat neonates and to rat insulinoma cells. Western blotting experiments revealed reaction to a 68-kDa protein from rat insulinoma cell extracts. This monoclonal antibody may have clinical relevance as it exhibits properties similar to the islet cell surface antibodies present in the sera of BB rats.

The role of viruses and environmental factors in the induction of diabetes

The development of IDDM results from the destruction of pancreatic beta cells. Genetic factors, various immune system alterations, and environmental factors have been studied as the possible causes of IDDM. The concordance rate for developing IDDM between monozygotic twins approaches 50%, suggesting that genetic factors are necessary, but nongenetic factors such as various immune system alterations and environmental factors also influence the clinical expression of genetic susceptibility. Environmental factors (e.g., viruses, chemicals, and diet) affecting the induction of diabetes may act as primary injurious agents which damage pancreatic beta cells or as triggering agents of autoimmunity. Certain viruses including EMC-D and Mengo virus 2T can directly infect pancreatic beta cells and replicate in the cells. The replication of viruses in the beta cells results in the destruction of the cells within 3 days, and the infected mice develop a diabeteslike syndrome in 3-4 days without the involvement of autoimmunity. In contrast, rubella virus appears to be somewhat weakly associated with autoimmune IDDM in hamsters. In addition, endogenous retrovirus expressed in pancreatic beta cells is clearly associated with the development of insulitis and diabetes in NOD mice. In man, there appears to be no correlation between the detection of islet cell autoantibodies and anti-Coxsackie B viral antibodies in newly diagnosed IDDM. In contrast, persistent infection of CMV and rubella virus appears to be associated with the presence of autoantibodies in newly diagnosed IDDM patients. It is particularly noteworthy that human CMV can induce islet cell autoantibodies that react specifically with a 38 kDa islet cell protein which may represent islet cell-specific antigens in a proportion of CMV-associated IDDM cases. These observations suggest that the association of diabetes with Coxsackie B viruses might be due to cytolytic infection of the beta cells with no link to autoimmunity, while both rubella virus and CMV are probably associated with autoimmune IDDM. A number of structurally diverse chemicals including alloxan, streptozotocin, chlorozotocin, Vacor, and cyproheptadine are diabetogenic mainly in rodents and sometimes in man. Possible mechanisms for beta cell destruction by these chemicals include (a) generation of oxygen free radicals and alteration of endogenous scavengers of these reactive species; (b) breakage of DNA and a consequent increase in the activity of poly-ADP-ribose synthetase, an enzyme depleting nicotinamide adenine dinucleotide in beta cells; and (c) inhibition of active calcium transport and calmodulin-activated protein kinase activity. (ABSTRACT TRUNCATED AT 400 WORDS)

A simple and versatile method for the preparation of vector-primers by adapter-end-primer ligation

A group of efficient cDNA cloning strategies employs vector-primers where cDNA synthesis starts from the oligo(dT)-primer tail, which is conventionally attached to cloning vectors by use of terminal deoxynucleotidyl transferase. An alternative, efficient and more versatile method of vector-primer preparation is to directly ligate, by use of T4 DNA ligase, a double-digested vector, e.g., pTZ18R/Pst I/Bam HI, to a synthetic (Bam HI)-adapter-end-primer, 5'-pGATCC-Tn or 5'-pGATCC-site-specific sequence. The use of a utility-vector containing a sizable spacer between the two selected restriction sites enables unambiguous separation on agarose gels of the double-digested vector precursors from single-digested ones, further simplifying the vector preparation. The adapter-end-primer ligation method can be applied to any suitable vectors with multiple cloning sites for the preparation of not only oligo(dT)-tailed, but also site-specific sequence-tailed vectors. Thus, the method enables the cDNA cloning of total poly (A+)-mRNAs, as well as specific RNA or mRNA species with or without poly(A)-tail.

Scrapie-induced diabetes mellitus in hamsters

Scrapie-infected hamsters had slightly elevated non-fasting plasma glucose levels, markedly abnormal glucose tolerance tests, and impaired release of insulin in response to a glucose load. Plasma cortisol levels were essentially the same in infected and uninfected animals. Histological examination of the pancreas revealed no morphological changes in infected animals with no alteration in distribution of cells secreting insulin, glucagon and somatostatin. In contrast, brains of scrapie-infected animals had the diffuse vacuolation typical of spongiform encephalopathy. These experiments suggest that scrapie-induced diabetes mellitus in hamsters may result from damage to the central nervous system.