Autoimmunological aspects of diabetes mellitus

B-cell function and islet cell and other organ-specific autoantibodies in relatives to insulin-dependent diabetic patients

The pancreatic B-cell function (glucose tolerance, C-peptide release) and organ-specific autoantibodies, including islet cell cytoplasmic and cell surface (mouse), were studied in 45 first-degree relatives of patients with insulin-dependent diabetes mellitus diagnosed before the age of 30 years. Compared to 107 healthy persons without any family history of either insulin-dependent or non-insulin-dependent diabetes mellitus, the prevalence of autoantibodies was increased among the relatives. The prevalence of islet cell antibodies did not differ between relatives and controls and none of the individuals had complement-fixing islet cell antibodies. There was no difference in glucose tolerance or C-peptide release between relatives and controls, whether they had autoantibodies or not. At a three-year follow-up, none of the individuals had developed insulin-dependent diabetes.

Addison's disease presenting in four adolescents with type 1 diabetes

Primary adrenocortical insufficiency (Addison's disease) is a potentially fatal condition that often develops insidiously and can be easily overlooked. Although rare in the general population, it is more common in patients with type 1 diabetes mellitus (T1DM). The combination of Addison's disease with T1DM and/or autoimmune thyroid disease is known as autoimmune polyendocrine syndrome type-2 (APS-2). T1DM commonly precedes the development of adrenocortical insufficiency in most patients with APS-2. We, in this study, present four cases of Addison's disease developing in adolescents with pre-existing T1DM. Risk factors for Addison's disease in this population include a history of other organ-specific autoimmunity, particularly thyroid, and a positive family history. In addition to the 'classic' Addisonian features, the development of unexplained recurrent hypoglycemia, reduction in total insulin requirement, improvement in glycemic control, or abnormal pigmentation should arouse suspicion of adrenocortical insufficiency. Adrenal antibodies have been proposed as a screening tool for Addison's disease in the T1DM population, but doubts remain about their specificity and sensitivity. The addition of specific HLA DRB1 subtyping has been proposed to improve predictive value.

Benzene--a review of the literature from a health effects perspective

A literature review of the impact on human health of exposure to benzene was conducted. Special emphasis in this report is given to the health effects reported in excess of national norms by participants in the Benzene Subregistry of the National Exposure Registry--people having documented exposure to benzene through the use of benzene-contaminated water for domestic purposes. The health effects reported in excess (p < or = .01) by some or all of the sex and age groups studied were diabetes, kidney disease, respiratory allergies, skin rashes, and urinary tract disorders; anemia was also increased for females, but not significantly so.

Thyroiditis in the BB rat is associated with lymphopenia but occurs independently of diabetes

The spontaneously diabetic BB rat is an excellent and well studied model for human insulin-dependent diabetes (IDDM), sharing many important features with the human disease. Similarities include an equal frequency of IDDM in males and females, production of antibodies against pancreatic cell antigens, and an MHC disease association. In addition, the BB rat shares with human IDDM patients an increased frequency of autoantibodies against the parietal cells of the stomach and colloid cells of the thyroid gland. Here we investigate the genetic basis of thyroiditis in the BB rat. Based on crosses between BB, Lewis and Fischer rats, we show that two susceptibility factors for diabetes--the lymphopenia trait present in diabetes prone BB rats and the MHC--also appear to be risk factors for thyroiditis. However, the nature of the susceptibility was different for the two autoimmune diseases, with lymphopenia being absolutely required for diabetes although it only conferred increased risk for thyroiditis. Also, in contrast to IDDM, the MHC conferred dominant susceptibility to thyroiditis. Despite these shared risk factors, diabetes per se did not show significant correlation with thyroiditis.

Pathogenesis of insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus is strongly associated with certain HLA types and the presence of islet cell-specific autoantibodies. The pathogenesis is a specific loss of pancreatic beta cells. The dissection of IDDM genes is complicated by the low recurrence rate of the disease among first-degree relatives. HLA-DQ2 and 8 are closest to IDDM with a marked synergistic effect of DQ2/8 heterozygotes. The associations with other HLA genes are often explained by linkage disequilibrium. Genetic factors on other chromosomes which influence the pathogenesis are still to be fully identified but candidates are on chromosomes 11 (insulin gene polymorphisms) and 7 (TCR gene polymorphisms). The autoreactivity against the GAD65 isoform is pronounced both before and at the clinical onset of IDDM. GAD65 autoantibodies show the highest predictive value and may represent an initiating autoantigen. Autoantibodies to numerous other beta cell autoantigens are detected at the clinical onset but may represent a secondary response and antigen spreading during a sustained autoimmune attack on the beta cells. The role of T cells in human IDDM is yet to be defined. GAD65 and other islet autoantibodies have a low positive predictive value for IDDM and further investigations are needed to clarify ways to predict IDDM in the general population.

The coexistence of systemic lupus erythematosus with other autoimmune diseases: the kaleidoscope of autoimmunity

Patients with systemic lupus erythematosis (SLE) often manifest features of other autoimmune diseases. In this review, we provide a detailed compendium of features of SLE that overlap with other conditions. This compendium is important because a critical feature in our understanding of autoimmunity has been the clustering of coexisting/different autoimmune diseases both within an affected patient and within a pedigree. Indeed, autoimmune disorders share a variety of similar clinical and serological defects. For example, all autoimmune disorders are associated with the elaboration of autoantibodies and/or the production of self-reactive mononuclear cell populations; many have high levels of immune complexes and defects in cell-mediated immunity. Several diseases share similar genetic backgrounds, as reflected by study of loci within the major histocompatibility complex. In part the coassociation is due to common genetic tendencies with different environmental precipitating agents (trigger mechanisms). It is likely that many factors can modulate the immune system to autoimmunity in the presence of an appropriate genetic background, eg, drugs, viral infections, UV irradiation, and toxins, ie, toxic oil syndrome and L-tryptophan-induced eosinophilic myalgia. The coexistence of SLE with other autoimmune diseases is an excellent venue to understand these events, and we believe that the presence of other autoimmune diseases in patients with SLE can be called the kaleidoscope of autoimmunity.

Type 1 diabetes and latent pernicious anaemia

OBJECTIVE

To determine the prevalence of latent pernicious anaemia (PA) in Type 1 diabetics.

DESIGN

Patients with Type 1 diabetes were screened at two yearly intervals on a continuing basis.

SETTING

Diabetic Unit, Royal Perth Hospital, Western Australia.

PATIENTS

Three hundred and seventy-one patients, 156 females and 215 males, attending a diabetic clinic. They were classified as having Type 1 diabetes on the basis of age of onset less than 40 years and requiring insulin from the start.

MAIN OUTCOME MEASURES

Serum cobalamin levels were measured and studies of thyroid function and a blood count were done. Patients with a reduced serum level of cobalamin had tests for cobalamin absorption.

RESULTS

Six patients had a low serum cobalamin level; five showed malabsorption of the vitamin which could be corrected by the addition of intrinsic factor. Four of these patients had no clinical signs of PA. The fifth was mildly anaemic (haemoglobin level 111 g/L) and had megaloblastic bone marrow. He was classified as having frank PA. The sixth patient was not available for further testing. These results give a prevalence of latent PA of 11 per 1000 in Type 1 diabetics, compared with 3.9 per 1000 in diabetics with clinically manifest disease and 1.27 per 1000 in the general population. All four patients with latent PA had hypothyroidism, based on low thyroxine levels, increased levels of thyroid stimulating hormone and the presence of thyroid antibodies.

CONCLUSION

Latent PA is not uncommon in Type 1 diabetics. It has a long preclinical course and occurs in those patients with thyroid disease. The screening of Type 1 diabetics for latent PA has worthwhile benefits as a "preventive" health measure.

Antithyroid and other organ-specific antibodies in Saudi Arab diabetic and normal children

Sera from 162 Saudi Arab children were examined for autoantibodies to thyroid microsomes, thyroglobulin pancreatic islet cells, gastric parietal cells, and adrenocortical cells. The subjects included a control group (n = 76) and 86 children below 14 years with Type 1 diabetes. Antithyroid antibodies were detected in 8.1% of the diabetic group and in none of the control group. Parietal cell antibodies were found in 9.3% of the diabetic group and 4.4% of the control group; 14.6% of diabetic children and 2.2% of control children were positive for islet antibodies. However, 56.3% (9/16) of those who were tested at onset of diabetes had positive islet antibodies. In none of the children could we detect adrenocortical cell antibodies.

Are thyrogastric autoantibodies associated with an increased susceptibility to developing type 1 (insulin-dependent) diabetes? A study in identical twins

To examine whether the presence of thyrogastric autoantibodies is associated with an increased susceptibility towards developing type 1 diabetes we have tested for thyroid (microsomal and thyroglobulin) and gastric-parietal cell antibodies in 86 pairs of identical twins, 47 discordant and 39 concordant for type 1 diabetes. Autoantibodies were detected in both twins of a pair in 35 and in neither twin in 45 pairs. In only 6 pairs (3 discordant) was there a discrepancy in the antibody results between co-twins. The frequency of antibodies was similar in twin pairs discordant, (21/44, 48%), and concordant, (14/36, 39%), for diabetes. Thyrogastric antibodies were not more frequent in pairs that were female, diagnosed above the age of 20, or had HLA DR3 as opposed to DR4. We conclude that thyrogastric autoantibodies are common in both type 1 diabetic patients and their non-diabetic identical twins. Their presence appears to be genetically determined but does not increase the susceptibility of developing diabetes. The presence of autoantibodies does not appear to indicate a separate aetiological type of diabetes.

Islet cell and other organ-specific autoantibodies in all children developing type 1 (insulin-dependent) diabetes mellitus in Sweden during one year and in matched control children

The majority (about 90%) of children developing Type 1 (insulin-dependent) diabetes mellitus do not have a first-degree relative with the disease. Nearly all (389/405, 96%) children (0-14 years) in Sweden, who developed diabetes during one year, were therefore studied to compare islet cell, thyroid peroxidase, thyroglobulin, and gastric H+, K+-ATPase antibodies with 321 age, sex, and geographically matched, but non-related, control children. Islet cell (cytoplasmic) antibodies were found in 81% (316/389) of the patients and in 3% (9/321) of the control children (p less than 0.001). The median islet cell antibody levels were 70 (range 3-8200) Juvenile Diabetes Foundation (JDF) Units in the islet cell antibody positive patients, and 27 (range 17-1200) JDF Units in the control children (NS). Autoantibodies against thyroid peroxidase (8%), thyroglobulin (6%), and gastric H+, K+-ATPase (3%) were all increased in the patients compared with the control children, being 2% (p less than 0.001), 2% (p less than 0.01), and 0.3% (p less than 0.01), respectively. During an observation time of 20-34 months, two of the nine islet cell antibody positive control children developed Type 1 diabetes, after 8 and 25 months respectively, while the others remained healthy and became islet cell antibody negative. None of the islet cell antibody negative control children developed diabetes during the same time of observation. This first investigation of an unselected population of diabetic children and matched control children shows: that islet cell antibodies are strongly associated with newly diagnosed childhood diabetes, that other autoantibodies are more frequent among diabetic children than control children, and that the frequency of islet cell antibodies in the background population of children is higher than previously documented, and could also be transient, underlining that factors additional to islet cell antibodies are necessary for the later development of Type 1 diabetes.

Immunological aspects of diabetes mellitus: prospects for pharmacological modification

It is now well known that insulin-dependent diabetes is a chronic progressive autoimmune disease. The prolonged prediabetic phase of progressive beta-cell dysfunction is associated with immunological abnormalities. A prediabetic period is suggested by the appearance of islet cell antibodies, anti-insulin antibodies, and anti-insulin receptor antibodies. The existence of activated T lymphocytes and abnormal T cell subsets are also other markers. There is still no concensus about the use of the immunosuppression superimposed upon conventional insulin therapy in early diagnosed IDDM and the follow-up of the relatives of IDDM patients who share the genetic predisposition and serological markers for the risk of future onset of IDDM. Treatment in the prodromal period cannot be justified because a link between the disease and early markers such as ICA has not been established with certainty (Diabetes Research Program NIH, 1983). Many immunopharmacological manipulations were reported to be effective in animal models. However, most of them are not readily applied to human subjects. Moreover, IDDM patients are now believed to be heterogeneous, with a complex genetic background. HLA-DR, and more recently DQ, are closely related to the genetic predisposition to IDDM but those genes are not themselves diabetogenic. The contribution of autoimmunity does not appear to be uniform, and in some cases, the contribution of virus is considered more important. There is a lack of a marker for the future onset of IDDM. ICA and ICSA were found after mumps infection, but the existence of those autoantibodies and even the co-existence of HLA-DR3 do not always indicate the future trend to insulin dependency. More precise markers will be disclosed through the biochemical analysis of the target antigens on pancreatic beta-cell for islet antibodies and effector T cells. Much safer and more effective immunopharmacological treatment will be developed through animal experimentation using rat and mouse models. The recent development and interest in this field will further facilitate the attainment of the goal for the complete prevention of IDDM.

Disappearance and reappearance of islet cell cytoplasmic antibodies in cyclosporin-treated insulin-dependent diabetics

In 68 newly diagnosed patients with insulin-dependent diabetes mellitus (IDDM) whose treatment included cyclosporin (CyA) the prevalence and mean titre of islet cell cytoplasmic antibodies (ICA) fell faster than they did in the 56 who received only insulin. However, in the CyA-treated patients the prevalence or titre of ICA at diagnosis did not correlate with beta-cell function as measured by glucagon-stimulated C-peptide levels; improvement and recovery of beta-cell function after 30 days of CyA therapy occurred despite the continued presence of ICA; and CyA-induced remission of IDDM (ie, glucagon stimulated plasma C-peptide levels greater than 0.6 pmol/ml) was not predicted by nor coincident with disappearance of ICA. Therefore, although CyA therapy was associated with a higher than expected frequency of remission and faster disappearance of ICA, the two observations were not temporally and may not be causally related. ICA should not be used to identify the target population for or to predict response to immunosuppressive therapy. The contribution of ICA to the pathogenesis of beta-cell destruction in IDDM needs serious re-examination.

Metabolic and immunological effects of cyclosporin in recently diagnosed type 1 diabetes mellitus

Cyclosporin 5-10 mg/kg daily was given for 2-8 months to twelve recently diagnosed type 1 diabetics from a mean of 49 +/- SE 14 days after the start of insulin therapy, which was regulated to give near-normal blood glucose and haemoglobin A1c values. Mean insulin dosage dropped from 46 +/- 5 U/day before cyclosporin treatment to 16 +/- 4 U/day by the 7th month. Four patients had a complete remission and the insulin needs of four more were cut by half. The remaining four did not have remissions. Initial basal and glucagon-stimulated C peptide concentrations were higher in those who went into remission than in those who did not; they rose during cyclosporin treatment in the former but not in the latter. OKT4+ lymphocyte functions were suppressed in all patients and OKT4/OKT8 ratios declined. Anti-beta-cell autoimmunity, as indicated by lymphocyte-induced inhibition of insulin release from mouse islet cells, declined in all patients who went into remission. No consistent trend was observed for anti-islet cell antibodies. In forty-four similar, but non-randomised, recently diagnosed diabetics treated with insulin alone, the incidence of remission was 6%.

Post-partum thyroiditis and goitrous (Hashimoto's) thyroiditis are associated with HLA-DR4

Using new panels of HLA-DR typing sera, we found an increase in the prevalence of HLA-DR4 in 21 patients with Hashimoto's thyroiditis (57%) and 32 patients with post-partum thyroiditis (53%) compared to controls (21%). Hashimoto's thyroiditis was previously found to be associated with HLA-DR5 and Dw5. We feel that the doubts raised by this study warrant the study of DR antigens in thyroid autoimmune disease using large panels of specific sera.

Immunological aspects of type 1 and 2 diabetes mellitus

IDDM occurs predominantly among individuals being class II antigen HLA-DR 3 and/or 4 positive, while NIDDM is not associated with HLA-D. Although the HLA-DR 3 or 4 specificities are prerequisites for IDDM to develop, their high frequencies (about 60%) in the background population preclude tissue typing as a predictive test, underlined by the observation that less than 50% of monozygotic twins are concordant for IDDM. The presence of a number of immune abnormalities argues that the causes of IDDM may be sought in an altered immune reaction against antigens present in the pancreatic B cells and/or in the environment. The majority of IDDM patients of short duration show both cellular and humoral autoimmunity against the pancreatic B cells. Similar phenomena may be observed in patients initially diagnosed as NIDDM and treated with oral hypoglycemic agents. It has been speculated that these patients have a retarded form of IDDM. It is possible that the combination of specific Class II antigen molecule(s) and an invading antigen (virus, bacterium, chemical etc.) presented to the immune system triggers the formation of effector cells such as B lymphocytes and cytotoxic T lymphocytes which also cross-react with the pancreatic B cells. Multiple exposures to this or related antigens throughout several years may eventually lead a sufficient loss of pancreatic B cells to cause insulin dependence.

Alterations in immunological function in streptozotocin-induced murine diabetes mellitus: correction by islet cell transplantation

Cell-mediated and humoral immune responses of streptozotocin-induced diabetic mice were evaluated using in vivo and in vitro immunological assays. C57BL/6 mice were rendered diabetic by a single intraperitoneal injection of 125-200 mg/kg of streptozotocin. Immunological studies were performed after the mice were diabetic (mean +/- SEM serum glucose 537 +/- 14 mg/dl) for a minimum of 4 weeks. Spleen cells from streptozotocin-induced diabetic mice exhibited significantly diminished direct IgM plaque-forming cell (PFC) responses following either in vivo or in vitro immunization with sheep erythrocytes, markedly impaired cytotoxic cell responses following in vivo or in vitro allogeneic stimulation, and diminished blastogenic response to the T-cell mitogens phytohemagglutinin and concanavalin A. In contrast the blastogenic response of diabetic spleen cells to lipopolysaccharide, a B-cell mitogen, was normal. The defects in in vivo PFC responses and in vivo cytotoxic cell responses were corrected by islet cell transplantation, suggesting that the abnormalities in immunological function of streptozotocin-induced diabetic mice are a consequence of the diabetic state and not of direct streptozotocin toxicity to lymphoid cells.

Polyglandular autoimmune syndromes

One of the basic caveats in endocrinology is that glandular abnormalities tend to occur together. Continued suspicion of other glandular hypofunction should be maintained in following patients with any type of endocrine gland hypofunction, since the risk of multiple glandular involvement is significant. Family members should be alerted to the high prevalence of endocrinopathies especially among first-degree relatives of patients with polyglandular autoimmune disease. Parameters such as antiorgan antibodies, although occasionally helpful, have not been shown to be consistently useful in predicting the future development of clinical organ-specific autoimmune disease. HLA typing remains a research tool at this time, as does evaluation of humoral and cell-mediated immunity.

Humoral autoimmunity in insulin-dependent (type I) diabetes mellitus. A current assessment

Autoimmunity plays a key role in the development of IDDM. Mediating an attack on the insulin-producing beta cell, autoimmune phenomena may be initiated by environmental factors or through loss of immunoregulatory control. A variety of antibodies directed against cytoplasmic and surface determinants of pancreatic islet cells have been associated with the onset of IDDM. Of these, ICSA are particularly of interest due to their preferential beta cytotoxic nature. Further elucidation of the immunologic events leading to IDDM represents the first step toward eventual therapeutic intervention in this disease.

Thyroid disease in diabetics

Among a diabetic clinic population of 5,000 there were 113 patients (1.1%) with concurrent clinical thyroid dysfunction (56 hyperthyroid, 57 hypothyroid). Seventy-one (62.8%) of these patients were insulin-dependent and diabetes preceded thyroid disease in 85 (75.2%). Twenty patients were given carbimazole for two or more years and of these 15 (75%) relapsed, a percentage not significantly different from that seen in non-diabetic patients. The value of screening diabetic patients for evidence of thyroid dysfunction is discussed.

Cell-mediated immunity and immune complexes in the pathogenesis of type 1 (insulin-dependent) diabetes

Evidence for a role of the immune system in the pathogenesis of insulin-dependent (Type 1) diabetes is now plentiful. In the light of the lymphocytic infiltration in the islets of Langerhans, different autoaggressive mechanisms have been suggested in the initiation of B-cell damage. Lymphocytes characterized by cytotoxic properties (K cells) and having receptors for the Fc of IgG are increased in newly diagnosed Type 1 diabetics. Circulating immune complexes are also raised in these patients at the time of clinical diagnosis and there is evidence that K cells bind immune complexes which can modulate the activity of these cells. Here we propose a possible interrelationship between K or Fc gamma receptor+ T lymphocytes and immune complexes which could have a 'key' role in the mechanism of activation of cell-mediated immunity towards B-cells.

Serum antibody responses to bovine retinal S-antigen and rod outer segments in proliferative diabetic retinopathy before and after argon laser photocoagulation

Using the enzyme-linked immunosorbent assay, the serum antibody titers to bovine retinal S-antigen and rod outer segments in pre- and post-argon laser treated diabetic retinopathy patients were compared to each other and to the titers of age- and sex-matched normal controls. The increase in anti-S titer following the initial laser treatment gave a P less than 0.01 using the two-tailed paired Student's t-analysis as compared to the prelaser anti-S titer. Both pre- and post-laser anti-S titers were elevated over normal controls with P values of less than 0.02 and less than 0.001, respectively. Eight weeks after the initial laser treatment, anti-S titers began to decline approaching control levels 12 weeks later. No significant change was found between pre- and post-laser titers when rod outer segments were used as antigen although the pre- and post-laser titers were increased over normal controls with P values of less than 0.05 and less than 0.001, respectively. The release and possible alteration of retinal components following photocoagulation may account for the rise in anti-S titers, while the prephotocoagulation titers may be due to retinopathy-related photoreceptor cell alteration.

Deficiency of suppressor T-cells in insulin-dependent diabetes mellitus: an analysis with monoclonal antibodies

Peripheral blood from 25 patients with insulin-dependent diabetes mellitus was examined for any alteration in the proportions and or functions of immunoregulatory T-cell subsets, defined with monoclonal antibodies. Ten of 25 (40%) patients demonstrated deficiency of OKT8+ (suppressor/cytotoxic) T-cells. Eight of these 10 patients had abnormally high ratios of OKT4+/OKT8+ T-cells. Nine of 10 patients with abnormally low proportion of OKT8+ T-cells had deficient concanavalin A-induced suppressor cell activity against the proliferative response of autologous or allogeneic lymphocytes to phytohemagglutinin. No correlation was observed between the deficiency of suppressor T-cells and the control of diabetes. Therefore, it is likely that the deficiency of suppressor cells is related to insulin-dependent diabetes mellitus itself and not to the metabolic changes that are associated with diabetes mellitus. This study demonstrates both quantitative and qualitative deficiency of suppressor T-cells in at least some patients with insulin-dependent diabetes, that might play an important role in the pathogenesis and autoimmune manifestations of a proportion of patients with insulin-dependent diabetes mellitus.

Diabetes mellitus in childhood

This review has attempted to highlight current views on the aetiology and management of children with type 1 diabetes mellitus. Emphasis has been placed on the management of ketoacidosis, the need for education and the use of home blood glucose monitoring. A perspective on new research direction has been given.

Organ-specific antibodies in healthy and diabetic children and young adults

160 children and young adults (aged 7-21 years) and 84 diabetics (aged 2-19 years) were screened for thyroglobulin (TgA), thyroid microsomal (MsA), smooth muscle (SMA), parietal cell (PCA), reticulin (RA), glomerular (GIA) and mitochondrial (MA) antibodies. The diabetics were also screened for islet cell antibodies (ICA). The overall incidence of other antibodies than ICA at the lowest serum titre studied was 18.1 percent for healthy children and 30.9% for diabetic children. The elevation in diabetics is significant (p less than 0.01). Females were overrepresented in both groups and had the highest titres of antibodies. The age group 10-14 years was observed to be a special time at which antibody titres became positive. As compared with the controls, diabetics exhibited an increased incidence of MsA (4.4 and 11.9% respectively, p less than 0.001), PCA (5.0 and 10.7% respectively, p less than 0.05) and RA (3.8 and 9.5% respectively, p less than 0.05). The presence of ICA or the duration of diabetes showed no correlation with other autoantibodies. The results indicate that autoantibodies at a low titre are a common phenomenon. Diabetics seem to be susceptible to react against their own tissue, which is probably associated with their increased frequency of autoimmune diseases.

Lymphocytes from diabetics suppress insulin release in vitro

The insulin response of isolated islet cells to glucose and theophylline in vitro was studied after incubation with lymphocytes. The test was employed to explore cell-mediated immunity in diabetics. A significant inhibition of insulin response to glucose and theophylline as compared to insulin release in a "basal" medium was found after incubation with blood lymphocytes from 21 out of 23 insulin-dependent diabetics (mean secretion index 18 +/- 18 versus 118 + 8 (SEM) % in control subjects). Most of the patients studied had associated autoimmune diseases: all of these displayed inhibition of insulin release. In six cases, the diabetes had a recent onset with no associated autoimmune disease: four of them displayed the same inhibition. No inhibition was found in the 26 control subjects and in seven non-insulin-dependent diabetics (mean secretion index 134 +/- 17 versus 145 +/- 23 (SEM) % in four control subjects). Lymphocytes inhibiting islet cell response were not cytotoxic against mouse fibroblasts. Twenty-two insulin-dependent diabetics showed islet cell antibodies to human and/or mouse pancreatic islets. However, an inhibition of insulin release was found with no detectable islet cell antibodies in one case, and the converse in two cases. Lymphocyte cytotoxicity to islet cells could play a role in the natural history of insulin-dependent diabetes.

Autoimmunity in insulin-dependent diabetes mellitus

Genetic susceptibility, environmental factors and immune mechanisms are implicated in the pathogenesis and etiology of insulin-dependent diabetes mellitus. The onset of the disease is associated with a major loss of beta cells, and inflammatory cells may be seen in and around the islets of Langerhans. Insulin-dependent diabetes is often associated with autoimmune endocrinopathies. Antipancreatic cell-mediated autoimmunity is found predominantly in young patients with insulin-dependent diabetes of recent onset as are antibodies reactive with cytoplasmic components or cell surface determinants of islet cells. Antibodies reactive with live islet cells may mediate complement-dependent cytotoxicity. The antigen(s) in the islet cells remain(s) to be identified and characterized. Further studies will be necessary to determine whether autoimmunity is the cause of beta-cell destruction or whether it is a consequence of damages caused by exogenous agents in susceptible persons.

HLA-Dw antigens in unrelated juvenile, insulin-dependent diabetics

Forty-one unrelated juvenile, insulin-dependent diabetics have been HLA tissue typed for A, B and Dw anitgens and compared with a normal control population. We have found statistically significant increases in the frequencies of B8, B18, and Dw3, and significant decrements in the frequencies of B7, B12 and Dw2. The log-linear modeling technique was used to study the association of JIDD with Dw3 and B8 antigens. We confirmed that the B8 excess seen in diabetics is secondary to the excess of Dw3. The decrements of B7, B12 and Dw2 could reflect an association of these antigens with a protective factor for the disease, or could be due to an artifact. The latter possibility was excluded for B7 and Dw2 by adjusting for the excess antigen frequencies. These findings suggest that the associations between the HLA and diabetes are compatible with the existence of genes which are concerned with the pathogenesis of the disease and are closely associated with the D locus of the major histocompatibility system.

Hereditary considerations in common disorders

We have reviewed the approach of the modern clinical geneticist to the genetics of common diseases. The importance of considering genetic heterogeneity within these groups of disorders has been emphasized. The physician should recognize our present inability to deliver exact recurrence risks for most families with these common disorders. As our knowledge improves, we must constantly update our counseling. Until then, in most cases, we can only utilize the empirical risk data presently available and provide an idea of the magnitude of risk, which in many of these disorders appears low. However, continued utilization of imprecise risk data must not impede recognition of potential and demonstrated heterogeneity within these disorders, or retard the development of new and improved risk data based on knowledge of the heterogeneity within common diseases.

Possible toxic effects of normal and diabetic patient serum on pancreatic B-cells

Serum from normal blood-donors and juvenile diabetic patients inhibited Rb+ accumulation and stimulated release of 51Cr and insulin in suspensions of dispersed pancreatic islet cells prepared from ob/ob mouse islets, which are rich in B-cells. The effects indicate the presence of a B-cytotoxic factor in human serum. Serum from mouse and fetal calf also inhibited the islet cell accumulation of Rb+. Toxicity was not suppressed by treating serum with protein A-Sepharose and did not correlate with islet cell binding of fluorescent antibodies to human immunoglobulin. Whereas all sera inhibited Rb+ accumulation, 3 of 6 diabetic patient sera, but no blood-donor serum, made the cells fluoresce on exposure to the fluorescent antibodies. Supporting a dependence on complement, toxicity remained after dialysis, but was destroyed by treating serum with zymosan-A or heating at 56 degrees for 30 min.

Studies on obesity. III. effect of triiodothyronine (T3) on thyroglobulin autoantibodies in euthyroid obese subjects

Effect of T3 therapy on tanned red cell agglutinating thyroglobulin (TRC-TG) antibodies in 10 obese subjects without apparent thyroid disease was investigated. Six other obese subjects without thyroid dysfunction and of approximately the same mean age who also had circulating TRC-TG antibodies served as control subjects and were untreated. In vitro thyroid tests (TSH, total and free T4) performed before T3 therapy, as well as clinical examination, showed thyroid function to be normal in all subjects, and there was no evidence of thyroiditis. TRC-TG antibodies were present in low to moderate titers of 40-1280 in control subjects as well as in subjects selected for T3 treatment. Therapy with T3 was started at 50 mug/day and gradually increased to a maximum of 250 mug/day, depending on clinical needs. T3-treated as well as untreated obese control subjects were all maintained on a high protein, low fat, low carbohydrate diet. Duration of T3 therapy varied from 2-8 mo, and in all but one T3-treated subject, TRC-TG antibodies completely disappeared. In the one exceptional case, TRC-TG antibody titer decreased from 1280 to 80 after 7 mo of therapy. In non-T3-treated obese control subjects, antibody titers remained at the same levels throughout the observation period, thereby indicating a lack of spontaneous regression of circulating immune response. Therapy with T3, by inhibiting TSH, may have caused regression of inapparent immunologic thyroid lesion, thus leading to the disappearance of circulating TRC antibodies; alternatively, T3 specifically may have accelerated catabolism of thyroid antibodies. The latter possibility is favored in the absence of clinical and laboratory evidence of thyroiditis in T3-treated subjects.