Biomedical subjects

J W Yoon

Publications and source records attributed to J W Yoon.

At least 73 records · Page 4Linked to original sources

PubMed1995

Cloning and expression of the VP1 major capsid protein of diabetogenic encephalomyocarditis (EMC) virus and prevention of EMC virus-induced diabetes by immunization with the recombinant VP1 protein.

The development of diabetes in mice induced by encephalomyocarditis (EMC) virus provides the best experimental evidence that viruses have an aetiological role in the pathogenesis of this disease. The major capsid protein (VP1) of EMC virus is important for both the attachment of the virus to pancreatic beta cells and for the determination of antigenicity. This experiment was initiated to clone the gene for the major capsid protein, VP1, of the diabetogenic EMC (EMC-D) virus, express the VP1 protein, and test whether the recombinant VP1 protein can prevent development of EMC-D virus-induced diabetes in mice. We successfully cloned the VP1 gene of the EMC-D virus in the expression vector pRSET and subsequently expressed the protein in Escherichia coli. The recombinant VP1 protein was then purified by affinity chromatography. Five- to six-week-old male SJL/J mice were immunized intraperitoneally with purified VP1 protein and then challenged after various intervals with highly diabetogenic EMC-D virus. None of the VP1-immunized mice developed diabetes, irrespective of the interval between immunization and virus challenge, whereas 80 to 95% of the EMC-D virus-infected control mice did develop diabetes. All of the VP1-immunized mice showed intact pancreatic islet architecture, whereas most of the infected control mice showed severe beta cell necrosis and lymphocytic infiltration of their pancreatic islets. On the basis of these observations, we conclude that the recombinant VP1 protein of EMC-D virus can completely prevent the development of EMC-D virus-induced diabetes in mice.

Amino Acid Sequence↗

PubMed1995

Beta cell-specific expression of retroviral mRNAs and group-specific antigen and the development of beta cell-specific autoimmunity in non-obese diabetic mice.

Non-obese diabetic (NOD) mice spontaneously develop autoimmune type 1 diabetes. Earlier studies have shown that retroviruses appear to be associated with the development of the disease in these animals. This investigation was initiated to determine whether any retroviral genes are specifically expressed in pancreatic beta cells from NOD mice, in contrast to their non-diabetic, parental strain, ICR mice. Host chromosomal DNAs from pancreatic islets, kidneys, hearts, and stomachs of NOD and ICR mice contained an equal amount of A-type retroviral genome (DNA); however, A-type retroviral gag, pol, and env mRNAs were detected in only the pancreatic islets from NOD mice. Furthermore, group-specific retroviral antigen (p73 of A-type--gag gene product) was found by immunofluorescent staining using anti-p73 antibody in only pancreatic beta cells from NOD mice. On the basis of these observations, we suggest that tissue and strain differences in transcription of the retroviral genome and beta cell-specific expression of A-type retroviral group-specific antigen p73 in NOD mice may be involved in the initiation of beta cell-specific autoimmunity leading to type 1 diabetes in these animals.

Animals↗

PubMed1994

Prevention of autoimmune type I diabetes in biobreeding (BB) rats by a newly established, autoreactive T cell line from acutely diabetic BB rats.

An autoreactive T cell line, BNY-2, was established from lymphocytes isolated from the islets of acutely diabetic BioBreeding (BB) rats after continuous stimulation of the isolated lymphocytes by irradiated lymph node cells. Flow cytometric analysis showed that BNY-2 cells were positive for CD4 and CD5 and were negative for CD8 and RT6, indicating that these cells were phenotypically Th cells rather than cytotoxic T cells. mAbs against rat MHC class II Ags (anti-RT1.D) blocked the proliferation response of BNY-2 cells, suggesting that these cells recognize the MHC class II Du molecule. When splenic T lymphocytes from diabetes-prone BB rats were stimulated by Con A in the presence of irradiated BNY-2 cells or irradiated lymph node cells, the BNY-2 cells had a significant suppressive effect on splenic T cell proliferation, whereas lymph node cells had no effect. When we injected diabetes-prone BB rats i.v. at 30 and 60 days of age with activated BNY-2 cells, the incidence of diabetes was significantly reduced compared with that seen in saline-injected control rats (diabetic incidences were 12 and 80%, respectively). On the basis of these observations, we conclude that autoreactive BNY-2 T cells, established from the pancreatic islets of acutely diabetic BB rats, can prevent the development of autoimmune diabetes in the diabetes-prone BB rat by an immunosuppressive effect.

Animals↗

PubMed1994

Effect of modification of connecting peptide of proinsulin on its export.

The production of a high yield of proinsulin using a secretion vector has been difficult, even with such modifications to the vector as a strong promoter and a good ribosome binding site. This investigation was therefore initiated to see whether modification of the connecting peptide of proinsulin has any effect on the export of proinsulin. We constructed three types of proinsulin secretion vectors: (a) pEZZ18-PI, by inserting the proinsulin gene into pEZZ18 vector; (b) pEZZ18-PI-C, by modifying ZZ-proinsulin by addition of the carboxy terminal peptide region of human insulin-like growth factor I (hIGFI) to the carboxy terminal end of proinsulin; and (c) pEZZ18-PI analogues, by sequentially deleting the connecting peptide region of proinsulin. The highest export yield of proinsulin was obtained when the connecting peptide region of the proinsulin was similar in size to that of hIGFI, or when most of the connecting peptide region of the proinsulin was deleted. The amount of exported ZZ-proinsulin analogues in these clones was over 25-times higher than that of ZZ-proinsulin with an unmodified connecting peptide in the secretion/expression vector pEZZ18-PI. On the basis of these observations, we conclude that modification of the mature domain of proinsulin is a critical factor for determination of the export of proinsulin.

Amino Acid Sequence↗

PubMed1994

Prevention of recurrent diabetes in syngenic islet-transplanted NOD mice by transfusion of autoreactive T lymphocytes.

Islet transplantation has been considered to be one of the best methods for the cure of type I diabetes, but transplanted islets are eventually destroyed by the host's cell-mediated autoimmune responses unless immunosuppressive agents are given. This investigation was initiated to develop a method for the prevention of beta cell destruction in transplanted islets without the use of immunosuppressive drugs. We have recently cloned CD4+ autoreactive T cells (NY1.1 and NY4.2) from lymphocytes infiltrating the pancreatic islets of nonobese diabetic (NOD*) mice and have shown that these cells respond to self MHC class II determinants. When the T cell clones (10(7) cells of either NY1.1 or NY4.2) were transfused into acutely diabetic NOD mice 2 to 3 days before transplantation of syngenic islets (400) into the subrenal space, the transplanted islets were not destroyed, and the animals maintained normoglycemia over 100 days without insulin treatment. In contrast, NOD mice that received syngenic islets (400) without the transfusion of an autoreactive T cell clone showed a recurrence of diabetes and massive mononuclear cell infiltration of the grafted islets within 17 days. On the basis of these observations, it is concluded that CD4+ autoreactive T lymphocytes can prevent the recurrence of insulitis and development of diabetes in pancreatic islet-transplanted NOD mice, without treatment with immunosuppressive drugs.

Animals↗

PubMed1994

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.

Amino Acid Sequence↗

PubMed1994

Complete nucleotide sequence of a strain of coxsackie B4 virus of human origin that induces diabetes in mice and its comparison with nondiabetogenic coxsackie B4 JBV strain.

The E2 strain of coxsackie B4 virus (CB4), which is of human origin, can induce a diabetes-like syndrome in mice. The cDNA of the genome of the E2 strain was cloned and sequenced. The E2 viral genome was found to comprise 7,396 bases, which appear to encode a polyprotein of 2,183 amino acids with an overall similarity of 94.91% to nondiabetogenic CB4 prototype JBV strain. The E2 genome is organized like other enteroviruses. It has a 5' noncoding region of 744 nucleotides, a single long open translational reading frame starting at nucleotide 745 and extending to nucleotide 7293, a 3' noncoding region of 100 nucleotides, and a poly (A) tract. Genomic sequence comparison of the E2 and JBV strains showed 1,369 nucleotide substitutions in the genome of the E2 strain, most of which are single and silent. There were 111 resultant amino acid changes arising from some of these substitutions, including 82 amino acid changes in the noncapsid proteins, and 29 amino acid changes in the capsid proteins VP1, VP2, VP3, and VP4, which showed 11, 13, 4, and 1 substitution(s), respectively. Noncapsid protein P2-C showed eight amino acid substitutions. On the basis of the sequence comparison of E2 and JBV strains of CB4, we suggest that some of the amino acid changes in the capsid and noncapsid proteins of the E2 strain may be involved in the determination of its diabetogenicity.

Amino Acid Sequence↗

PubMed1994

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.

Animals↗

PubMed1994

Studies on autoimmunity for initiation of beta-cell destruction. X. Delayed expression of a membrane-bound islet cell-specific 38 kDa autoantigen that precedes insulitis and diabetes in the diabetes-prone BB rat.

The diabetic syndrome in the DP-BB rat results from progressive beta-cell destruction by autoimmune responses. However, the initial events causing the autoimmune destruction of beta cells remain largely unknown. Our recent experimental results suggest that the delayed expression of a beta-cell-specific autoantigen may result in the initiation of beta-cell-specific autoimmunity. The present investigation was initiated to identify such an autoantigen. Islets were isolated from DP-BB rats of several different ages, and protein extracts from the membrane fraction of the islet preparations were immunoprecipitated with sera from diabetic DP-BB rats. We have found that a membrane-bound islet cell-specific 38 kDa autoantigen is not expressed early in the life of DP-BB rats, but is delayed-expressed by approximately 30 days of age, the time at which immunological effectors begin to recognize beta cells. In contrast, a 64 kDa islet cell protein is expressed from birth in DP-BB rats. On the basis of these observations, we suggest that delayed expression of a gene encoding for the membrane-bound islet cell-specific 38 kDa autoantigen may result in a breakdown of self-tolerance, leading to beta-cell-specific autoimmune IDDM in the BB rat.

Aging↗

PubMed1993

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.

Animals↗

PubMed1993

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.

Animals↗

PubMed1993

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.

Animals↗

PubMed1993

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.

Alanine↗

PubMed1992

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.

Adolescent↗

PubMed1992

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.

Animals↗

PubMed1992

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.

Animals↗

PubMed1991

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.

Animals↗

PubMed1991

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.

Animals↗