Fine-root mortality rates in a temperate forest: estimates using radiocarbon data and numerical modeling.

* We used an inadvertent whole-ecosystem 14C label at a temperate forest in Oak Ridge, Tennessee, USA to develop a model (Radix1.0) of fine-root dynamics. Radix simulates two live-root pools, two dead-root pools, non-normally distributed root mortality turnover times, a stored carbon (C) pool, and seasonal growth and respiration patterns. * We applied Radix to analyze measurements from two root size classes (< 0.5 and 0.5-2.0 mm diameter) and three soil-depth increments (O horizon, 0-15 cm and 30-60 cm). * Predicted live-root turnover times were < 1 yr and approximately 10 yr for short- and long-lived pools, respectively. Dead-root pools had decomposition turnover times of approximately 2 yr and approximately 10 yr. Realistic characterization of C flows through fine roots requires a model with two live fine-root populations, two dead fine-root pools, and root respiration. These are the first fine-root turnover time estimates that take into account respiration, storage, seasonal growth patterns, and non-normal turnover time distributions. * The presence of a root population with decadal turnover times implies a lower amount of belowground net primary production used to grow fine-root tissue than is currently predicted by models with a single annual turnover pool.

Greening of the land surface in the world's cold regions consistent with recent warming.

Global ecosystem function is highly dependent on climate and atmospheric composition, yet ecosystem responses to environmental changes remain uncertain. Cold, high-latitude ecosystems in particular have experienced rapid warming1, with poorly understood consequences2-4. Here, we use a satellite observed proxy for vegetation cover - the fraction of absorbed photosynthetically active radiation5 - to identify a decline in the temperature limitation of vegetation in global ecosystems between 1982 and 2012. We quantify the spatial functional response of maximum annual vegetation cover to temperature and show that the observed temporal decline in temperature limitation is consistent with expectations based on observed recent warming. An ensemble of Earth system models from the Coupled Model Intercomparison Project (CMIP5) mischaracterized the functional response to temperature, leading to a large overestimation of vegetation cover in cold regions. We identify a 16.4% decline in the area of vegetated land that is limited by temperature over the past three decades, and suggest an expected large decline in temperature limitation under future warming scenarios. This rapid observed and expected decline in temperature limitation highlights the need for an improved understanding of other limitations to vegetation growth in cold regions3,4,6, such as soil characteristics, species migration, recruitment, establishment, competition, and community dynamics.

Predictive value of gastric parietal cell autoantibodies as a marker for gastric and hematologic abnormalities associated with insulin-dependent diabetes.

The frequency and significance of gastric parietal cell autoimmunity was assessed in 771 patients with insulin-dependent diabetes (IDD) of onset before 30 yr of age. Gastric parietal autoantibodies (PCA) were found 4 times more frequently in the patients with IDD (9%) than among 600 matched nondiabetic controls (2%). Caucasian female patients with IDD had PCA twice as frequently as male patients. Thyroid microsomal autoantibodies were more frequent in patients with IDD and PCA, than in those with IDD alone (Caucasian 46% versus 18%, black 25% versus 2.5%). A history of pernicious anemia and/or PCA was found in 25 or 40 families of IDD probands with PCA. Achlorhydria was demonstrated in 6 of 11 patients (54%) with PCA but in none of seven IDD patients without PCA. The six patients with achlorhydria had significantly lower uptakes of oral radiolabeled cobalamin, lower serum cobalamin levels, lower intrinsic factor-R protein ratios in their gastric aspirates, and lower plasma ferritin levels than patients with IDD but without PCA. None of the study group had IF antibodies in their serum or gastric juice. Overt pernicious anemia and neuropathy were found in one patient with PCA. Young patients with IDD at risk for atrophic gastritis and cobalamin deficiency can initially be identified by screening for PCA. Many of these young patients with PCA already have achlorhydria and evidence of decreased absorption of cobalamin. These patients can then be followed with cobalamin levels and/or with complete blood counts to identify those requiring therapy.

The diabetogenic effects of streptozotocin in mice are prolonged and inversely related to age.

Single "subdiabetogenic" doses of streptozotocin (SZ), when given to young male CD-1 mice, produced a delayed onset of hyperglycemia dependent on the dose of SZ and on the age of the mice. The effect was markedly reduced or absent in older mice given the same dose of SZ per kg of body weight. Histologic examination of the pancreas of these animals revealed that SZ induced greater damage to the islets of the young mice compared with older mice. In addition to the characteristic findings of a decrease in insulin-containing cells and an increase in glucagon- and pancreatic polypeptide-containing cells there was evidence of new islet formation. Delayed-onset hyperglycemia was also induced in young inbred DBA/2J, C57BL/KsJ, and SWR/J mice with single SZ doses as well as with alloxan in young CD-1 mice, indicating that the effect was not specific for CD-1 mice not for SZ as the agent inducing beta-cell injury. The induction of beta-cell autoimmunity did not appear to be important in the delayed diabetogenic effect of SZ, since insulitis was rare and followed the onset of hyperglycemia when seen, and islet cell autoantibodies were not found. Rather, SZ induced more beta-cell destruction in young animals than in older mice, and the continued somatic growth of the former suggests that the delayed hyperglycemia was due to an out-growing of a reduced insulin supply. That mild to severe diabetes could be induced by the same dose of SZ/kg, depending only on the age of the mice when SZ was given, may have implications for understanding the apparent heterogeneity of human diabetes mellitus.

Pancreatic alpha cell autoantibodies and glucagon response to arginine.

The frequency and significance of cytoplasmic pancreatic alpha cell autoantibodies (ACA) were investigated in 2102 healthy controls, 879 patients with insulin-dependent diabetes mellitus (IDDM) who were negative for islet cell autoantibodies (ICA), and 1567 relatives of IDDM patients. ACA were found in approximately 1 in 200 people of all ages and were not significantly associated with IDDM, the IDDM-associated HLA phenotypes DR3 and DR4, or thyrogastric or adrenal autoantibodies. Of 11 ACA-positive patients studied by arginine stimulation tests, none had frank glucagon deficiency. Thus, ACA do not appear to be associated with defective alpha cell function or with IDDM.

Lymphocyte subsets and activation in prediabetes.

Peripheral blood lymphocytes were obtained from 65 individuals: 34 nondiabetic patients with islet cell autoantibodies (ICA) (prediabetic phase), 9 patients with newly diagnosed insulin-dependent diabetes mellitus (IDDM), 6 ICA-negative siblings or offsprings of IDDM patients, and 16 ICA-negative controls. The presence of lymphocyte abnormalities and/or activation was examined with dual fluorescence flow cytometry. The percentages of B cells, total T-lymphocyte, and helper T-lymphocyte (Th) and cytotoxic/suppressor T-lymphocyte (Tc/s) subsets and their ratio were not significantly different among the patient groups. No increased expression of interleukin 2 receptor on T-lymphocyte was found in newly diagnosed IDDM or prediabetic individuals. Sixteen of 49 patients had significantly increased number of T-lymphocyte expressing HLA-DR. A significant increase in the number of both Th and Tc/s subsets expressing HLA-DR was found in only 3 of 16 patients. This increase was unrelated to the patients's relative ICA titer or HLA-DR phenotype. On the other hand, the relative density of the DR antigen (RAD-DR) was significantly increased on both Th (886 +/- 120) and Tc/s (1250 +/- 273) in 13 of 38 patients compared with control patients (Th 484 +/- 129 and Tc/s 460 +/- 166). The RAD-DR on Tc/s correlated with the relative ICA titer and was greatest on DR3/4-phenotyped T-lymphocytes. In addition, significantly increased RAD-DR was found in noncontrol patients with impaired insulin release responses at 1 and 3 min to intravenous glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Islet cell and other organ-specific antibodies in U.S. Caucasians and Blacks with insulin-dependent diabetes mellitus.

Islet cell antibodies (ICA) were detected in 168 (33%) of 504 patients with insulin-dependent diabetes mellitus (IDDM). Mean age of onset of IDDM was 8.6 +/- 0.2 yr and mean age at testing was 13.4 +/- 0.3 yr. None of 162 controls without diabetes (mean age 21.8 +/- 0.9 yr) had ICA. Caucasian patients (404) had a 74% frequency of ICA within 3 mo of diagnosis and an overall ICA frequency of 36%. These results were similar to those reported from Europe. Black patients (100) had lower frequencies of ICA (P < 0.01) and thyroid antibodies (P < 0.05). Caucasian patients with onset of IDDM before 5 yr of age (107) had a lower frequency (P < 0.01) of ICA (21%) than those (297) with a later age of onset (42%). Patients with persistent ICA beyond 5 yr of IDDM had increased frequencies of gastric parietal and adrenal cortex cell antibodies. Thyroid microsomal antibodies were less frequent (P < 0.05) in blacks (4%) than in Caucasians (20%). The former did not have adrenal antibodies. Similar ICA frequencies among Caucasians with IDDM in the U.S. and in Europe suggest that etiologic factors are similar in the two geographic regions. The lower frequencies of ICA in patients with IDDM onset before 5 yr of age suggest that some of these patients may have a different etiology and/or a more rapid disappearance of islet cell antigens than patients with a later onset.l The lower ICA frequencies in black patients can be explained by heterogeneity of IDDM in this group and by admixture of IDDM susceptibility genes from the Caucasian genome to the black genome.

CD5+ B lymphocytes in high-risk islet cell antibody-positive and newly diagnosed IDDM subjects.

Human CD5+ B lymphocytes produce autoantibodies that bind to self- and exogenous antigens. Extremely high percentages of CD5+ B lymphocytes are present in the fetal and newborn periods, whereas they constitute only a minority of B lymphocytes in healthy adults. Increased percentages of circulating CD5+ lymphocytes have previously been demonstrated in several autoimmune diseases, including rheumatoid arthritis, progressive systemic sclerosis, Graves' disease, and Sjögren's syndrome. We measured the percentages of B lymphocytes that expressed the CD5 determinant in 93 control subjects (age range 1 day to 59 yr, mean +/- 22.6 +/- 17.7 yr), 17 subjects with newly diagnosed insulin-dependent diabetes mellitus (IDDM; range 5-29 yr, mean +/- SD 13 +/- 5.9 yr), 31 high-risk islet cell antibody (ICA)-positive nondiabetic subjects (range 4-45 yr, mean +/- SD 19.8 +/- 14.1 yr), and 13 subjects with IDDM of greater than 5 yr duration (range 10-43 yr, mean +/- SD 24.2 +/- 9.9 yr). We report that CD5+ B-lymphocyte percentages are strikingly age dependent in healthy control subjects, declining progressively from the newborn period to the middle-age years (r = -0.75, P = 0.0001). In ICA+ nondiabetic and recent-onset IDDM subjects less than 29 yr of age, the percentage of circulating CD5+ B lymphocytes fell within the 95% confidence intervals established for control subjects. However, the age-dependent rate of decline in the percentage of CD5+ B lymphocytes within the control range was slower in ICA+ and newly diagnosed IDDM subjects than in control subjects.

Are insulin autoantibodies markers for insulin-dependent diabetes mellitus?

Recent studies have shown that insulin autoantibodies occur in patients with newly diagnosed insulin-dependent diabetes mellitus (IDDM) before exogenous insulin treatment. Our study was designed to test the hypothesis that insulin autoantibodies, like cytoplasmic islet cell antibodies (ICAs), can identify individuals with ongoing autoimmune beta-cell destruction and increased risk of IDDM development. Insulin autoantibodies detected by use of a radioligand-binding assay were found in 1.4% of normal controls, 4% of first-degree relatives of IDDM patients, and in 37% of newly diagnosed IDDM patients. A strong positive correlation between insulin autoantibodies and ICAs was observed. HLA typing of insulin-autoantibody-positive first-degree relatives of IDDM patients, as well as in the general population, revealed a strong association with HLA-DR3 and/or-DR4, suggesting that insulin autoantibodies are restricted to persons genetically susceptible to IDDM. In an ongoing study of beta-cell function in ICA-positive nondiabetic individuals, the additional presence of insulin autoantibodies significantly increased the likelihood of beta-cell dysfunction. After intravenous glucose stimulation, insulinopenia was present in 70% of ICA and insulin-autoantibody-positive individuals in contrast to only 23% of ICA-positive, insulin-autoantibody-negative persons. These data document a significant association between insulin autoantibodies and ICAs and support the contention that insulin autoantibodies, like ICAs, are markers of ongoing beta-cell destruction.

Competitive insulin autoantibody assay. Prospective evaluation of subjects at high risk for development of type I diabetes mellitus.

A quantitative fluid-phase radioassay for autoantibodies reacting with insulin (competitive insulin autoantibody assay, CIAA) was developed. The assay's features include 1) use of a physiologic amount of 125I-labeled insulin, 2) parallel incubations with supraphysiologic cold insulin (competitive), and 3) an incubation time of 7 days and a single-step multiple-wash polyethylene glycol separation. Mean +/- SE CIAA levels in 50 controls were 8 +/- 1.4 nU/ml (range -16-33.3). In 36 cytoplasmic islet cell antibody (ICA)-positive nondiabetic first-degree relatives of type I (insulin-dependent) patients less than 30 yr of age, CIAA levels exceeded the normal range in 20 (55.6%) of 36 (mean 86.8 +/- 17.1 nU/ml). In 26 ICA-positive relatives greater than 30 yr of age, only 5 (19.2%) of 26 exceeded the normal range (mean 26.1 +/- 9.4 nU/ml); P less than .001 compared with younger ICA-positive relatives). Six ICA-negative HLA-identical siblings of type I diabetic patients had normal CIAA levels (mean 3.6 +/- 5.8 nU/ml), and only 2 of 13 ICA-negative identical twins discordant for diabetes (mean 15.4 +/- 6.6 nU/ml) exceeded the normal range. Nine (50%) of 18 ICA-positive schoolchildren exceeded the normal range (mean 105.3 +/- 36.7 nU/ml). Genetically susceptible subjects negative for CIAA (with only 3 exceptions) remained negative for CIAA on multiple determinations (3 conversions observed), and CIAA levels of positive subjects were relatively stable. Linear regression of the first CIAA level versus last (interval between sampling 1 mo to 10 yr) in genetically susceptible individuals showed a highly significant correlation (r = .95, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic marker associations with proliferative retinopathy in persons diagnosed with diabetes before 30 yr of age.

It has been suggested that HLA-DR4 is a marker of genetic predisposition to proliferative retinopathy. To investigate this relationship and potential associations between other polymorphic genes and proliferative retinopathy, a sample (n = 428) of participants in the population-based Wisconsin Epidemiologic Study of Diabetic Retinopathy was selected for typing for HLA-A, -B, -C, and -DR and a panel of other polymorphic genes. The presence of proliferative retinopathy was determined from grading of stereoscopic color fundus photographs taken at 2 examinations, 4 yr apart. In logistic regression models with repeated measures, persons with HLA-DR4 who were negative for DR3 were five times more likely to have proliferative retinopathy than those negative for both antigens after adjusting for other potential risk factors (Odds ratio = 5.43, 95% Confidence Interval (Cl) = 1.04, 28.30). HLA-C2, AK-2, and MNSs-S also were associated positively with proliferative retinopathy, and HLA-DR8 was associated inversely with this complication of diabetes in each case before adjusting for the number of comparisons. These data suggest that the genetically determined immunopathic mechanisms leading to diabetes, and in linkage disequilibrium with DR4, may independently contribute to the development of proliferative retinopathy.

Metabolic and underlying causes of diabetes mellitus.

It is emphasized that animal models should be used to study specific genotypic or phenotypic expressions associated with diabetes rather than assuming a single animal model can reflect diverse forms of the human disease. Diabetic and normal animals are reviewed on the basis of their usefulness as models of genetic, viral, and chemically induced diabetes, including the often associated immune phenomena. Characteristics of spontaneously diabetic animals with and without obesity are also described with an emphasis on both genetics and metabolic derangements. Recommendations for future animal experimentation include: more longitudinal studies evaluating the role of sex, prenatal environment, diet, and viral or chemical attack on B-cell function; characterization of the immune phenomena associated with B-cell lesions (and insulitis) in diabetic and immunologically incompetent lines; clarification of relationships between obesity and islet-cell function with emphasis on the role of fuel metabolism, vitamins, and minerals; and, finally, the development of new models with specific genetic aberrations placed in normal or diabetic lines.

Thyroid, gastric, and adrenal autoimmunities associated with insulin-dependent diabetes mellitus.

Thyroid microsomal, gastric parietal, and adrenocortical autoantibodies were sought in 1456 Caucasian and 240 black patients with insulin-dependent diabetes mellitus (IDDM), in 1467 of the Caucasian patients' immediate family members, and in 1519 normal Caucasian control subjects. Positive clinical significances and predictive values of these autoantibodies for associated gland dysfunctions were found. In all groups, thyroid and gastric autoantibodies were more common in female subjects. In the control group, thyroid and gastric autoantibodies were more frequent with advancing age, affecting more than one-third of Caucasian women after age 60 yr. This age-augmented increase occurred very prematurely in patients with IDDM and their relatives. Among the patients with IDDM and thyroid and gastric autoantibodies, these autoantibodies appeared by the time of onset of IDDM in the large majority of cases; however, they were more common among patients with later ages of onset of IDDM. Occurrence of thyroid and gastric autoantibodies in 404 siblings of patients with IDDM was not affected by their degree of HLA-haplotype sharing with their diabetic sibling, suggesting that the inherited predisposition to thyroid and gastric autoimmunity is not HLA-related. In light of this, the increased frequencies of these antibodies in patients with IDDM and their relatives suggest that "thyroid and gastric autoimmunity genes" may also predispose to IDDM.

Development of IDDM after donating kidney to diabetic sibling.

The goal of this study was to describe a patient who developed insulin-dependent diabetes mellitus (IDDM) after donating a kidney to his sibling and to suggest a possible solution to prevent such an occurrence. A 42-yr-old man was found to have islet cell autoantibodies (ICAs) as part of a screening program of first-degree relatives with IDDM. Two years previously, he had donated his kidney to his HLA-identical sibling with long-standing IDDM. Both oral and intravenous glucose tolerance tests demonstrated a gradual loss of insulin secretion and increasing glucose intolerance until the patient developed IDDM 6 yr after the nephrectomy. Whether the presence of ICA is an absolute contraindication to being a kidney donor could be debated. Nonetheless, ICA should be used as a screening test to identify individuals at risk for subsequent IDDM. For those found to be positive, counseling should be provided.

Ambulatory diabetes management by a pulse of subcutaneous insulin delivered by a portable pump: preliminary report.

Two teenage patients, who had severe psychosocial problems that complicated their diabetes management, were treated for one month (14-year-old girl) and two months (16-year-old boy) by frequent pulses of insulin injected subcutaneously by a portable, programmed pump. Additional pulses were manually adjusted by the patient before eating. Both patients experienced improved sense of well-being, marked reduction in urine volume and in glycosuria, and reduced glycemic excursions and average levels. The boy had accelerated linear growth and a decreas in HbA1 percentage. Despite marked clinical improvement, permitting return to school, the girl was impelled to interrupt pump administration after two weeks. Both patients continue to use the device voluntarily; a smaller unit, however, that doesn't have the conspicuous external controls, would likely be readily acceptable to most young patients.

Psychological impact of islet cell-antibody screening. Preliminary results.

The identification of at-risk individuals before the onset of insulin-dependent diabetes mellitus with islet cell-antibody (ICA) screening programs could have significant psychological sequelae. We initiated a descriptive study of ICA+ subjects and their family members in which reactions to study participation, anxiety, and coping responses are monitored. Described here are preliminary results from 18 ICA+ youngsters, 6 ICA+ adults, and their family members. ICA+ identification resulted in clinically significant anxiety that dissipated to normal levels over time for all participants. Both ICA+ subjects and family members coped with the news in similar ways, relying primarily on problem-focused and social-support coping strategies. Few blamed themselves for their own or their loved one's ICA+ status. There was some evidence that the ICA+ participants may minimize the potential impact of their at-risk status. Compared with family members, ICA+ subjects used more avoidance coping strategies, and few believed they would ever develop diabetes. In contrast, many family members believed their loved one would ultimately develop diabetes. Although the initial findings support the resiliency of this population, the long-term effects of ICA screening remain to be seen.

Limited joint mobility in childhood diabetes: family studies.

We examined 204 persons with insulin-dependent diabetes mellitus (IDDM), aged 7-23 yr, and 336 of their first-degree relatives, to determine whether there is a genetic component to the development of limited joint mobility. Simple and multiplex pedigrees with IDDM were studied along with normal controls. Only 1 of 90 normal controls had joint stiffness. Among 225 nondiabetic parents of children with IDDM, 7 (3%) had joint limitation, compared with 42 (21%) of children and youth with IDDM. Only 1 of 108 nondiabetic siblings of diabetic probands had limitation. Three parents had adult-onset diabetes and all had limited joint mobility. None of the 8 nondiabetic relatives with joint limitation had diabetic probands with joint involvement; 5 of these 8 tested were negative for islet cell auto-antibodies. There were 11 IDDM multiplex families with at least one member having joint limitation. The concordance rate for limited joint mobility of persons with diabetes for more than 5 yr who were over 12 yr of age was 56%, not different from the 48% frequency in patients with IDDM who met these age and duration criteria. Thus, evidence that limited joint mobility is a metabolic consequence of diabetes includes the virtual absence of limitation among first-degree relatives of probands, including probands with joint stiffness, and that the frequency of joint involvement is not increased in first-degree relatives of patients with IDDM. Furthermore, two brothers with pancreatic hypoplasia and a non-HLA-associated form of IDDM were affected with limited joint mobility. Nonetheless, the expression of this complication must be influenced by host factors, since not all persons with IDDM develop it, and those who do have variable ages of onset without correlation to control measures.

Different HLA haplotypes in Mexican Americans with IDDM.

The study of HLA histocompatibility antigens and insulin-dependent diabetes mellitus (IDDM) in non-White populations may provide a unique opportunity to more accurately define the diabetes susceptibility gene(s) located within the HLA region. To determine whether HLA haplotypes differ between ethnic groups, we compared 105 HLA haplotypes from 55 Mexican-American IDDM patients with 272 haplotypes from 136 IDDM patients of non-Hispanic White descent. The accurate determination of genotypes and haplotypes requires the study of family units. Therefore, all diabetic patients in this study were from studies of families having one or more siblings with IDDM. In the Mexican-American group, HLA-DR3 and -DR4 were the most common HLA-DR alleles and were present in comparable frequencies in the non-Hispanic White group (HLA-DR3, 27% of Mexican-American and 29% of non-Hispanic White haplotypes; DR4, 46% of Mexican-American and 43% of non-Hispanic White haplotypes). However, the HLA-B/DR-containing haplotypes and haplotype frequencies differed between the two groups. Several common haplotypes (B8/DR3, B15/DR4) in the non-Hispanic White group occurred less frequently in the Mexican-American group. In contrast, uncommon haplotypes in the non-Hispanic White group comprised nearly 50% of the DR4-containing haplotypes (B35/DR4, B40/DR4, B44/DR4) in the Mexican-American group. Although both DR3- and DR4-haplotype frequencies differed significantly between the two groups, the relative frequency of DR3- but not DR4-containing haplotypes was similar in both ethnic groups. This adds to the evidence suggesting that different susceptibilities are provided by the haplotypes carrying the DR3 and DR4 alleles.

Standardization of IVGTT to predict IDDM.

OBJECTIVE: To review current practice in centers that use the IVGTT for prediction of IDDM. To establish consensus protocol for performance of the test. RESEARCH DESIGN AND METHODS: Postal questionnaires were delivered to 12 centers. RESULTS: Eleven centers used a glucose dose of 0.5 g/kg and 1 used 0.3 g/kg; the dosage in adults was limited to a maximum of 25-50 g in some centers but others applied no upper limit. The glucose concentration of the infusate varied between 20 and 66%. Eight centers injected glucose manually, two used a syringe pump, and two used gravity infusion. The period of infusion ranged from 30 +/- 10 s to 4 +/- 2 min, and time zero was taken as the start (1 center), middle (1 center), or end (10 centers) of the infusion. The potential range in timing of the +1-min sample varied between 1 and 7 min from the start of the infusion. Quality-assurance standards for the insulin assays used were not always appropriate for the fasting and low stimulated range of insulin levels. CONCLUSIONS: The first-phase insulin response to the IVGTT is widely measured as an index of risk of progression to IDDM. We established that methodology varies widely. Because of this, a new standard protocol for use in prediction of IDDM was agreed by an ICARUS working group and is described herein.

Inherited susceptibility to autoimmune Addison's disease is linked to human leukocyte antigens-DR3 and/or DR4, except when associated with type I autoimmune polyglandular syndrome.

The inherited susceptibility to autoimmune Addison's disease was found to be strongly associated with human leukocyte antigens (HLA)-DR3 and DR4 alleles. In a study of 45 white patients from the United States with the disease, the relative risks (the number of times that an individual is at risk for Addison's disease if they had a marker, compared to those without such marker) were found to be 6.0, 4.6, and 26.5 for the DR3 allele, the DR4 allele, and for DR3/DR4 heterozygotes, respectively. Frequencies of DR2, DR5, and DR7 in the patients with Addison's disease were significantly decreased in comparison to 265 individuals in the control population. These HLA-DR frequencies in patients with Addison's disease were similar to those for 723 patients with insulin-dependent diabetes (IDD). However, the above HLA-DR associations persisted even when only data from the 37 patients with Addison's disease who did not have IDD were considered. Adrenocortical autoantibodies in 23 patients with IDD who did not have Addison's disease were equally frequent among those with DR4 and DR3 alleles. In contrast, HLA-DR frequencies in 17 patients with type I autoimmune polyglandular syndrome (chronic mucocutaneous moniliasis, hypoparathyroidism, Addison's disease, etc.) were not different from control. We conclude that genetic susceptibility to autoimmune Addison's disease may involve the same HLA-associated genetic determinants as IDD, except when Addison's disease occurs as part of type I autoimmune polyglandular syndrome.