Spontaneous diabetes mellitus syndrome in the rat. I. Association with the major histocompatibility complex.

A syndrome of spontaneous diabetes mellitus has been previously described in a partially inbred rat strain called BB Wistar. We have determined whether there is major histocompatibility complex (MHC) linkage as well as other predisposing haplotype-associated factors of development. BB rats are RT1 (MHC) genotype u/u. Using BB x Lewis F1 hybrid matings, an F2 study analyzed 128 rats from 8 primary and 3 additional litters from a breeding pair producing a diabetic offspring. 4 of 128 F2 rats, all from the 48 progeny of same breeding pair, became clinically diabetic. The four diabetics were all genotype u/u (P = 0.03). In the primary F2 litters, haplotype distribution was not different from the 1:2:1 expected ratio. However, in the four litters from the from the F1 breeding pair producing diabetics, there was an increased number of u/u animals. Two-way analysis of variance revealed significant differences in pancreatic insulin content between litters (diabetics excluded), P less than 0.001, and between haplotypes P less than 0.007 with heterozygous u/u less than 1/1 progeny. The glucagon content showed no significant differences. These data demonstrate (a) MHC linkage with spontaneous diabetes in this rat model; (b) penetrance similar to the human disease; and (c) a possible association of MHC haplotype with pancreatic inflammation as well as insulin content in nondiabetic F2 siblings.

Dendritic cell-lymphoid cell aggregation and major histocompatibility antigen expression during rat cardiac allograft rejection.

To determine the pattern of cellular expression of donor MHC class I and class II antigens during the course of rat cardiac allograft rejection, ACI cardiac allografts transplanted to BN recipients were examined from day 2 to day 6 using immunohistologic and immunoelectron microscopic methods. We used both monomorphic and donor-specific mouse anti-rat MHC class I and class II mAbs in this study. In normal ACI hearts, MHC class I reactivity was confined to the vascular endothelium and to interstitial cells. Ongoing rejection was characterized by an increased donor MHC class I staining intensity of microvascular endothelium and induction of donor class I surface reactivity on cardiac myofibers. Donor MHC class II reactivity was exclusively confined to interstitial dendritic cells (IDC) in both normal ACI hearts and in rejecting allografts, although rejection was associated with marked fluctuations in class II IDC frequency. An early numerical depression in class II IDC present in both allografts and syngeneic heart grafts was attributed to a direct effect of the transplantation procedure. By days 3-4, allografts showed an absolute overall increase in donor class II IDC frequency, which was associated with the presence of multiple localized high-density IDC-lymphocyte aggregates. The lymphocytes present in the focal areas were predominantly of the class II-reactive Th cell subpopulation. These aggregates may thus represent the in vivo homologue of dendritic cell-lymphocyte clustering, which has been shown to be required for primary class II allosensitization in the rat and mouse in vitro. During the late phase of rejection, there was a marked numerical fall in donor class II IDC, which correlated with extensive overall graft destruction. This study has shown that acute rat cardiac allograft rejection can occur in the absence of donor MHC class II expression by allograft vascular endothelium and cardiac myofibers. The IDC, which are believed to represent the principal class II alloantigen presenting cells in the rat heart, remain the sole class II-expressing cellular constituents of the graft throughout the course of rejection.

Renal transplantation in the inbred rat. 3. A study of heterologous anti-thymocyte sera.

Heterologous rabbit anti-rat thymocyte sera, its immunoglobulin G fraction, and the bivalent and univalent antibody fragments obtained by pepsin digestion are potent immunosuppressive reagents when tested in a system of renal allotransplantation between the LBN F(1) hybrid and Lewis rat strains. The AT F(ab')(2) is not lymphocytotoxic in vitro but has agglutinating ability, while the AT Fab' neither agglutinates nor is cytotoxic to rat lymphocytes, but will inhibit the in vitro reaction. The AT IgG and the F(ab')(2) are more immunogenic in their host than normal rabbit IgG and F(ab')(2), probably due to increased delivery of the antibody to the immune system. Donor pretreatment studies demonstrate that a cross-reacting, highly immunogenic antibody with anti-lymphocyte specificity may bind to renal sites and be transferred to the new host after transplantation. In addition, the crude unabsorbed anti-thymocyte antisera may induce a nephritis characteristic of immune complex disease which can be eliminated by complete absorption with serum proteins. Further in vivo and in vitro evidence is presented that the AT IgG contains small amounts of antibody to glomerular basement membrane antigens and may induce an autologous phase-nephrotoxic nephritis. The amount of in vivo binding by AT IgG to GBM was reduced by subcutaneous rather than intravenous administration. Most of the rabbit antisera tested contain antibody in low titer to sheep erythrocytes and in vivo experiments indicate that the nature of the immunodepressive effect of AT globulin to sheep erythrocytes is due in part to the passive transfer of antibody and is not necessarily due to a specific anti-lymphocyte effect.

Immune dysfunction in diabetes-prone BB rats. Interleukin 2 production and other mitogen-induced responses are suppressed by activated macrophages.

Spleen cells of diabetes-prone BB Wistar rats were found to generate excessively low proliferative responses, and interleukin 2 (IL-2) levels in response to T-dependent mitogens. This abnormality was not due solely to abnormal T cell numbers since: (a) addition of BB spleen cells of BB splenic macrophages to normal major histocompatibility complex (MHC)-matched Wistar Furth (WF) spleen cells resulted in severe suppression of concanavalin A (Con A)-, phytohemagglutinin (PHA)-, and pokeweed mitogen (PWM)-mediated proliferation, and IL-2 production; (b) macrophage depletion from BB spleen cells, but not B cell or T cell depletion, removed completely the suppressive effects of BB cells on WF cells; (c) macrophage depletion greatly enhanced the response of BB lymphocytes to T-dependent mitogens. Although suppressor macrophages could also be found in the spleen of WF control rats they were present in much smaller numbers than in the spleen of BB rats. The suppressive effect of BB macrophages was partially reduced by addition of the prostaglandin synthetase inhibitor indomethacin to cultures. Furthermore, indomethacin (but not catalase or PMA) considerably augmented IL-2 secretion of Con A-stimulated BB spleen cells, but had little effect on WF spleen cells. In contrast, prostaglandins E1 and E2 (PGE1 and PGE2) suppressed IL-2 production. While IL-2 secretion was severely depressed in BB rats unstimulated and lipopolysaccharide (LPS)-stimulated IL-1 secretion by splenic macrophages was normal. BB macrophages did not inactivate IL-2. Low IL-2 production and macrophage-mediated suppression were features of all BB rats tested.

Pathogenesis of a local graft versus host reaction: immunogenicity of circulating host leukocytes.

A local invasive-destructive reaction typical of that seen in allograft rejection occurs when Lewis rat spleen cells are inoculated under the capsule of Lewis kidney freshly grafted into F(1) hybrid hosts. Thus the donor lymphoid cells can be immunogenically stimulated by circulating host leukocytes and the interaction of these two cell populations results in nonspecific damage to kidney parenchyma. The results indicate that passenger leukocytes in organ allografts may be important immunogenic agents.

Insulin-dependent diabetes mellitus is associated with genes that map to the right of the class I RT1.A locus of the major histocompatibility complex of the rat.

Previous studies have demonstrated that the presence of at least one u-haplotype of the rat major histocompatibility complex (MHC), RT1, is a necessary but not sufficient condition for the development of overt diabetes mellitus. The present studies were undertaken to determine which portion of the RT1 gene complex is necessary for the occurrence of diabetes. We crossed hooded diabetic rats (RT1.AuBuDu) with PVGr8 rats (RT1.AaBuDu). F1 animals were mated to give 82 F2 animals and backcrossed with the hooded diabetics to produce 41 backcross animals. Diabetes occurred in animals with all three possible RT1.A genotypes. The diabetes was similar to that seen in BB rats and in hybrid strains developed from them. An immunoregulatory defect was marked by decreased percentage of peripheral blood lymphocytes staining with w3/25 monoclonal antibody, by an increased percentage of peripheral blood lymphocytes binding a mouse ascites control protein, and by decreased responsiveness of peripheral blood lymphocytes to stimulation by concanavalin A. We conclude that the u-allele of the class I A-locus gene product is not necessary for susceptibility to the development of diabetes in the rat. Therefore, either genes coding for the class II products of the u-haplotype or genes in linkage disequilibrium with these genes and mapping to the right of the A locus provide the permissive condition. Furthermore, the data suggest, but do not prove, that the u-haplotype derived from a strain remote from the BB rat can confer this susceptibility to the development of diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Major histocompatibility complex restriction of T-lymphocyte responses to islet cell antigens in IDDM rats.

BBUF rats, derived from BB rats, spontaneously develop a form of insulin-dependent diabetes mellitus (IDDM) associated with infiltration of the islets of Langerhans by lymphocytes (insulitis). BBUF rats bear the RT1u major histocompatibility complex (MHC) haplotype that we have shown to be necessary for the expression of this form of IDDM. A T-lymphocyte line obtained from the pancreas of a diabetic rat (UPCC.5) and three T-lymphocyte hybridomas derived by fusing T-lymphocytes of BBUF rats (MUS1.2, MUS1.13, and MUP3.21) respond to islet cell antigens in an MHC-restricted way. UPCC.5 responds to a combination of islet cell antigens (ICAg) and antigen-presenting cells by proliferation, whereas the T-hybridoma responses are detected on the basis of IL-2 production in a similar assay. This study reveals that an antiserum against mu-haplotype MHC antigens or a monoclonal antibody against the product of the D class II subregion of the rat MHC could inhibit ICAg recognition. A monoclonal antibody against the product of the B class II MHC subregion of the rat was not inhibitory. These results suggest that RT1.D antigens (analogous to human DR and mouse I-E) restrict islet cell recognition in this rat model of spontaneous IDDM.

Two-color flow cytometry analysis of activated T-lymphocyte subsets in type I diabetes mellitus.

We addressed the question of whether newly diagnosed type I (insulin-dependent) diabetes mellitus patients showed an increased number of DR (la+) T-lymphocytes compared with nondiabetic siblings and normal control subjects. Two-color flow cytometry measurements of peripheral-blood lymphocytes showed a slight but statistically significant increase in DR+ T-lymphocytes in diabetic subjects as well as the nondiabetic sibling control compared with the normal control subjects. This difference was not present in long-term-diabetic subjects. Thus, in addition to minor changes in this lymphocyte subset in peripheral blood, the sibling data demonstrate a lack of specificity for the disease; therefore, these measurements are probably of limited diagnostic usefulness.

Polygenic nature of spontaneous diabetes in the rat. Permissive MHC haplotype and presence of the lymphopenic trait of the BB rat are not sufficient to produce susceptibility.

We describe the phenotypic characteristics of animals in the fifth backcross-intercross generation of a breeding program in which the RT1 u haplotype and the phenotypic trait responsible for the T-lymphopenia of BB rats have been transferred to the ACI background. In this generation of animals, 24% were lymphopenic with decreased numbers of PBL expressing CD5, TCR alpha, and RT6. The PBL of the lymphopenic animals had a decreased mitogenic response to ConA. All of the nonlymphopenic animals were homozygous for RT6.2. Phenotypic analysis of intestinal IEL revealed that this was also the case for the lymphopenic animals. Moreover, IEL of the lymphopenic animals exhibited a pattern of staining (increased numbers of TCR alpha beta+CD4+CD8+ and decreased numbers of TCR alpha beta+CD4-CD8+) similar to that of BB DP animals. The ACI.1U(BB)-lymphopenic animals, although having two of the genetic traits associated with the expression of spontaneous diabetes mellitus, uniformly fail to develop diabetes. Breeding studies in which these animals were crossed with BB and hBB rats suggest that other genes are necessary for development of overt diabetes.

Interferon-gamma induces transcription and differential expression of MHC genes in rat insulinoma cell line RINm5F.

We have reported that enhanced levels of class I major histocompatibility complex (MHC) antigen are expressed throughout the islets of prediabetic and newly diabetic BB rats and that the endocrine cells of the islet remained class II negative. In this study we investigated the molecular biology of lymphokine-induced expression of the class I and II MHC genes in subclones of the rat insulinoma cell line RINm5F. Treatment of a particular subclone of RINm5F cells (which are normally class II negative, class I low expressors) with crude lymphokine preparation or various doses of recombinant interferon-gamma resulted in enhancement of MHC class I antigen expression but no detectable induction of class II antigen expression. This enhancement of class I antigen expression was a dose-dependent phenomenon and was preceded by a dose-dependent increase in class I-specific RNA. Both class I and II genes were induced at the transcriptional level, as determined by Northern blotting and in vitro nuclear transcription assays, but exhibited strikingly different induction kinetics. Supernatants from concanavalin A-stimulated splenocytes had a similar class I-restricted inductive effect on MHC gene expression. This subclone of RINm5F cells, which exhibits a class I lymphokine response-positive, class II response-negative phenotype, 1) mimics the behavior of beta-cells in the prediabetic and newly diabetic pancreas and 2) represents a valuable system for probing the similarities and differences in the lymphokine-mediated induction pathways for class I and II MHC genes.

Isolation of T-lymphocyte lines with specificity for islet cell antigens from spontaneously diabetic (insulin-dependent) rats.

T-lymphocyte lines specific for islet cell antigens were isolated from the spleen and pancreas of newly diabetic BB rats or from the related strain BBUF. These cell lines were grown in continuous culture with interleukin-2 (IL-2) containing medium for greater than 60 days. Such T-lymphocytes responded by proliferation and IL-2 secretion in the combined presence of islet cell antigens and major histocompatibility (MHC)-matched antigen-presenting cells. By fluorescence-activated cell sorter (FACS) analysis the cells were W3/13+, W3/25+, and OX8-. Thus, both functionally and by cell-surface-marker analysis they appear to be of the T-helper phenotype. The long-term growth and study of anti-islet T-lymphocyte lines will permit a detailed analysis of the role of T-lymphocytes in the pathogenesis of IDDM.

IDDM in BB rats. Enhanced MHC class I heavy-chain gene expression in pancreatic islets.

Modulation in major histocompatibility complex (MHC) gene expression correlates with the inflammatory reactions that occur during graft rejection and autoimmune disease. We analyzed the expression of class I and II MHC genes in the pancreatic islets of prediabetic and newly diabetic BB rats by immunohistochemistry of tissue sections and Northern blotting of RNA extracted from isolated islets. We show that enhanced levels of MHC class I heavy-chain RNA are present in pancreatic islets before overt inflammation and the onset of insulin-dependent diabetes mellitus (IDDM) in the spontaneously diabetic BB rat. Immunohistochemical analysis revealed enhanced class I antigen expression throughout the pancreatic islets of newly diabetic animals but no induction of class II antigen on endocrine cells within the islet. Varying degrees of inflammatory infiltrate were observed in the sections exhibiting enhanced class I antigen expression or in nearby serial sections. Southern blot analysis revealed no restriction-fragment-length polymorphism or amplification of the endogenous class I heavy-chain genes compared with those of seroidentical disease-resistant Wistar-Furth rats. I-A alpha and I-E alpha hybridizing RNA appeared de novo before overt diabetes, although concomitantly with T-lymphocyte-receptor beta-chain and interferon-gamma gene hybridizing RNA and after MHC class I heavy-chain RNA enhancement was observed. These data indicate the possibility that enhanced class I heavy-chain gene expression plays a role in the progression of IDDM.

Association of susceptibility to spontaneous diabetes in rat with genes of major histocompatibility complex.

This study was designed to map the diabetes susceptibility gene(s) associated with the rat major histocompatibility complex (MHC) RT1. We have crossed spontaneously diabetic male rats bearing the recombinant RT1r8 haplotype with female rats of the AC1.1r4 congenic strain. Three diabetic rats were determined to be homozygous for the r4 haplotype by serotyping. The absence of recombination within the MHC was confirmed by inspection of restriction-fragment-length patterns of the diabetic animals and the parental strains. In conjunction with previous breeding studies, this study maps the diabetes susceptibility gene to the right of the RT1-A locus and to the left of the RT1-C locus. A low incidence of diabetes in the F2 (4.5%) emphasizes the multifactorial nature of the susceptibility. The presence of depressed responsiveness of peripheral blood lymphocytes to concanavalin A stimulation increases the prevalence of the overt disease. An unusual feature of the diabetic syndrome in this study is the sparse or absent pancreatic lymphocytic inflammatory response, with true insulitis being a rare finding.

Immunologic and genetic studies of diabetes in the BB rat.

The spontaneous development of diabetes in the Bio-Breeding (BB) rat is an excellent model of human insulin-dependent diabetes mellitus (IDDM). Disease expression is dependent on several genetically determined abnormalities, including specific major histocompatibility complex (MHC) genes. At least one MHC class II locus of the U haplotype is a necessary, but not sufficient, condition for disease expression. The immune system of BB rats is markedly abnormal. There is a striking reduction in the number and function of mature cytotoxic/suppressor T cells, a poor proliferative response to mitogens and in mixed lymphocyte culture, poor interleukin-2 production, and a reduced ability to reject skin allografts. While these immune system abnormalities are closely related to the development of diabetes, the immune recognition and effector mechanisms resulting in islet cell destruction are still poorly understood. The hypothesis that MHC class II induction on pancreatic beta cells serves to target these lymphokines, natural killer (NK) cells, macrophages, etc.) have been implicated in islet cell killing. The incidence of IDDM is reduced by immunosuppressive therapy in both rats and humans, further supporting the role of immune mechanisms in this disease.

Association of spontaneous thyroiditis with the major histocompatibility complex of the rat.

Overt insulin-dependent diabetes mellitus in the rat is associated with the u haplotype of the rat major histocompatibility complex (MHC), RT1. Thyroiditis of sufficient severity to result in elevation of TSH levels is seen in Buffalo rats (RT1b). In order to examine the association of autoimmune thyroid disease with MHC gene products, we have crossed inbred Buffalo rats with diabetic BB rats and examined the RT1 genotype, the histology of thyroid and pancreatic tissue, and two indices of thyroid function. The data indicate that animals having pancreatic lymphocytic infiltration and insulinopenic overt diabetes mellitus had at least one RT1u haplotype. All but one animal having severe histological thyroid lymphocytic infiltration had at least one RT1b haplotype. Rats with severe thyroiditis had higher mean TSH levels than rats with normal histology or rats with mild thyroiditis. We conclude that gene products of the rat MHC affect the severity of spontaneous organ-specific autoimmune disease in terms of clinically apparent as well as tissue inflammatory disease.

A genetic survey of rat cardiac allograft rejection in presensitized recipients.

A genetic study of cardiac allograft rejection in 24 rat strain combinations sensitized by skin graft immunization has revealed that all grafts are rejected in either accelerated or hyperacute fashion. In the four strain combinations tested, the BN strain responded by rejection in hyperacute manner and the ACI strain was highly immunogenic in four strain combinations. No evidence for genic interaction was revealed by presensitization when the parental L and Bf or LBf F1 strains were studied with WfBN F1 recipients. The Lewis strain, used in many enhancement studies with BN or LBN F1 did not react with hyperacute rejection when immunized with BN. F1 hybrid to F1 hybrid haplotype-matched combinations showed accelerated rejection only. In a segregating backcross population of (L X LACI)F1, hyperactue rejection was associated with disparity at the Ag B (H-1) locus. It is concluded that the rat is a suitable species for studies of hyperacute rejection if the proper strain combination is chosen; strain-specific immune responsiveness, as well as disparity at the major histocompatibility complex and antigen dose, may be a factor in producing the phenomenon.

In vitro correlates of rejection. II. Rat mixed lymphocyte reactivity in vitro and cardiac allograft acute rejection, hyperacute or accelerated rejection, and prolongation by active immunization.

The relationship of F1 hybrid to parental strain cardiac allograft rejection rates to mixed lymphocyte reactivity in vitro has been studied in 10 strain combinations crossing the major histocompatibility barrier in three different models of acute rejection, accelerated or hyperacute rejection after skin graft immunization, and attempted active enhancement using 10(7) donor strain bone marrow cells. Although high and low reactivity could be discerned between the F1 hybrid and reciprocal parental strain in three of five instances in the one-way lymphocyte culturr reaction, low reactivity was only associated with prolonged graft survival in one combination. Two strain combinations giving high in vitro lymphocyte responses were associated with easily enhanced grafts. The BN strains was a low responder in vitro in the three combinations tested and as a recipient strain, allografts could not be actively enhanced. After skin graft presensitization, BN recipients rejected grafts hyperacutely in two of three combinations and with a median survival time of 2 days in the third combination. The association of poor in vitro proliferative responses, the inability to induce enhancement, and rapid graft rejection after skin graft presensitization could be related to genetic mechanisms controlling the amount and class or subclass of antibody or to the generation of suppressor cells and remains to be determined.

Mixed leucocyte interaction suppression generated after alloimmunization.

Utilizing a bone marrow cell immunization protocol designed to actively enhance renal or cardiac allografts, the in vitro mixed lymphocyte interaction has been studied. After immunization with allogeneic cells over a wide dose (10(5) to 10(8)) and time range, the mixed lymphocyte interaction using peripheral blood lymphocytes is reduced, and this reduction is shown in mixing experiments to be attributable to a circulating suppressor cell that has adherence characteristics of T lymphocytes. Specificity for in vivo generation of these circulating cells as well as specificity in the in vitro reaction was shown, although a nonspecific suppression background was observed. Allogeneic thymocytes, splenocytes, and platelets were effective in immunizing to generate these cells also. There was no general correlation with the ability to generate these cells and to actively enhance cardiac allografts, since suppression was seen after alloimmunization in strain combination that cannot be actively enhanced.

Genetic analysis of reactivities of allospecific monoclonal antibodies to rat histocompatibility antigens.

The reactions of a number of LEW anti-ACI allospecific rat monoclonal antibodies were examined in a series of breeding studies. Analysis of (LEW X ACI) F2 progeny demonstrated concordance of the monoclonal class I and class II specificities with results of conventional alloantisera typing. In addition, a "gene dosage" effect was noted, with a/a homozygotes showing approximately twice the reactivity as a/l heterozygotes. The previously noted crossreaction of antibody 36.3 (anti-RT1.Aa) with WF and RP strains segregated with RT1.Au in (WF X ACI) F2 and (LEW X RP) F2 progeny suggesting structural similarity of these two allelic products. Finally, an apparent decreased reaction of two (WF X ACI) F2 offspring with antibody 36.3 was shown to be heritable to the F5 generation and may represent an example of genetic control of level of expression of a class I antigen.

Differential susceptibility of cardiac cell populations to in vitro immune injury.

In vitro, the culture of enzymatically dissociated fetal heart cells results in the formation of contractile cellular islets surrounded by monolayers of static cells. The islets contract in a spontaneous and synchronous fashion. Using inbred strains of rats sensitized by an allogeneic heart transplant or by three consecutive skin grafts, immune sera were obtained that were assayed at various dilutions against the cell cultures with or without complement. Strain-specific and selective lysis exclusively directed against the static cells was observed. This suggests that noncontractile cells were the specific targets for alloantibody in this fetal heart cell culture system.