Lack of immune responsiveness to bovine serum albumin in insulin-dependent diabetes

Anti-BSA antibodies do not cross-react with the 69-kDa islet cell autoantigen ICA69

In contrast to several previously published reports, we demonstrate by a variety of antibody assays that bovine serum albumin (BSA) is not antigenically cross-reactive with the 69-kDa islet cell autoantigen (ICA69). Fast protein liquid chromatography purified BSA and highly purified recombinant human ICA69 were used to establish sensitive Western blot and ELISA assays in order to detect antibodies against these two proteins. The assays excluded BSA or powdered milk as blocking agents, since these would interfere with antibody binding. A panel of sera from diabetic individuals, first degree relatives, and normal controls showed that the majority (approximately 70%) of individuals from each group had antibodies against ICA69 as assayed by Western blots, whereas considerably fewer (approximately 13%) had anti-BSA antibodies on Western blots, and individuals with antibodies to both proteins occurred only rarely (2-3%). To explore this issue further we immunized a total of 16 individual rats, representing four different strains (bio-breeding diabetes resistant and diabetes prone, Wistar-Furth, and Sprague-Dawley), with either BSA (n = 2 of each strain) or with recombinant ICA69 (n = 2 of each strain), and for each animal pre- and postimmune antibody titres against BSA and against ICA69 were assayed separately by enzyme-linked immunoabsorbent assay. In rats immunized with BSA, anti-BSA titres increased about 100,000-fold over preimmune levels, whereas anti-ICA69 reactive antibodies were unchanged over preimmune levels. Similarly, in rats immunized with ICA69, anti-ICA69 titres rose about 100,000-fold over preimmune levels, whereas anti-BSA antibodies were unchanged over preimmune levels. Thus we find no evidence for the existence of antibody cross-reactivity between ICA69 and BSA, either in humans or in immunized rats. When our rat anti-BSA antisera were used to probe Western blots made from rat islets isolated in the strict absence of fetal calf serum, we were unable to detect a 69-kDa band, even when the islets were preincubated with gamma-interferon, a treatment which has been reported to induce the BSA cross-reactive islet antigen. We conclude that BSA is not antigenically cross-reactive with ICA69 at the antibody level, and it is highly unlikely that BSA is antigenically cross-reactive with some other 69 kD islet cell antigen.

Amamentação ao seio, amamentação com leite de vaca e o diabetes mellitus tipo 1: examinando as evidências

A etiologia do diabetes mellitus tipo 1 (DM1) envolve tanto herança genética como a exposição a fatores ambientais. Evidências de estudos epidemiológicos e experimentais sugerem que a dieta pode ser importante na etiopatogenia dessa doença. Em 1984, Borch-Johnsen e col. sugeriram, com base nos resultados de um estudo caso-controle, que o leite materno seria um fator de proteção para o DM1; esse efeito se daria devido às propriedades anti-infecciosas desse tipo de leite, ou pelo fato de que a amamentação ao seio evitaria que as crianças pudessem ser precocemente expostas a outros agentes etiológicos contidos nos substitutos do leite materno. Esses mesmos achados foram poste-riormente encontrados em diversos estudos, mas o papel do leite materno no aparecimento do DM1 ainda permanece controverso. Em 1992, Karjalainen e col., ao compararem os soros de indivíduos com e sem DM1, observaram, entre os diabéticos, altas concentrações de anticorpos anti-albumina bovina. Os autores postularam a hipótese de que a albumina bovina poderia atuar como desencadeadora do processo destrutivo das células ß do pâncreas e, conseqüentemente, do diabetes. Resultados conflitantes foram observados nas publicações que se sucederam a essa. Neste artigo, resumem-se e discutem-se os achados de diferentes pesquisadores que investigaram a importância desses fatores dietéticos para o aparecimento do DM1.

Cellular immune reactivities in women with silicone breast implants: a preliminary investigation

BACKGROUND

Surgical implantation of silicone breast prostheses has been conducted and considered safe for over 30 years. Some implant recipients, however, complain of a group of symptoms similar to those observed in connective tissue disorders, rheumatoid arthritis, systemic lupus erythematosus, or polymyositis. To date, immunologic sequelae have not been confirmed and remain controversial.

OBJECTIVE

To examine an autoimmune-like basis for the "silicone associated disease" reported by some women with silicone breast prostheses.

METHODS

Proliferative responses of peripheral blood mononuclear cells against a panel of control and connective tissue proteins and to compounds common to silicone prostheses were measured in 26 women who received silicone breast implants (with implants in place an average of 166.4 [standard deviation (SD) 58.3] months), and 23 age-matched and sex-matched healthy controls.

RESULTS

The frequency and intensity of cellular immune responses against collagen I, collagen III, fibrinogen, and fibronectin were significantly increased in silicone breast implant recipients versus controls. In implant subjects, the highest frequency of immune reactivity was directed against collagen I (11/26, 42%) with collagen III being the most immunostimulatory self-antigen with a mean stimulation index (SI) of 8.2 [95% confidence interval (95% CI) 3.2]. In addition, 10/26 (39%) of the implant recipients responded to more than one of the connective tissue antigens versus 0/23 (0%, P = .0007) healthy controls. Immunologic reactivities to other antigens, including silicone-based compounds, were remarkably similar.

CONCLUSIONS

The identification of self-reactivity towards these connective tissue antigens may provide important information for attempts at associating silicone breast implants with disease.

Aspects of the etiology, prediction, and prevention of insulin-dependent diabetes mellitus in childhood

This article focuses on recent developments that have defined the autoimmune nature of this entity and its genetic basis, especially the crucial roles of aspartic acid at position 57 of the DQ beta chain and arginine at position 52 of the DQ alpha chain of the HLA complex on chromosome 6 in conferring susceptibility; other genetic markers on other genes are mentioned. These genetic markers help to explain the worldwide differences in prevalence and incidence of type 1 diabetes. Because the autoimmune process may be gradual, markers of beta pancreatic cell damage, such as islet cell antibodies, glutamic acid decarboxylase antibodies, and insulin autoantibodies, coupled with evidence of progressive failure of insulin secretion may be used to predict the future onset of disease. In turn, accurate prediction may permit preventive intervention. Two intervention trials are mentioned: (1) Diabetes Prevention Trial for Type 1, a multicenter trial in the United States using insulin; and (2) European Nicotinamide Diabetes Intervention Trial in Europe using nicotinamide as the preventive or delaying agent. These first steps reflect the remarkable progress and understanding of this major problem of childhood and the hopes for its future prevention.

Activation of CD8+ T lymphocytes in insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is a T-cell-mediated autoimmune disease directed against the insulin-secreting beta cells of the islets of Langerhans of the pancreas. We have previously shown that in organ-specific autoimmune diseases, Graves' disease (GD), and IDDM, the antigen that is specific for each of these disorders (i.e., TSH receptor for GD, glutamic acid decarboxylase-65 (GAD65) for IDDM) does not activate the disease-specific CD8+ cells as fully as CD8+ cells from normal persons. In order to identify the specific antigen responsible for triggering or maintaining autoimmunity in patients afflicted with the disease, we have studied the effects of islet (beta) cell-specific antigens GAD65, insulin, pancreatic antigen (P69), T cell epitope 69 (Tep69), and a milk-derived bovine serum albumin (BSA)-peptide-ABBOS (pre-BSA positions 157-169) on the activation of CD8+ T lymphocytes in IDDM patients. We compared the patterns of T cells activation with those mediated by an irrelevant peptide antigen, P348 (amino-terminal region of human cardiac myosin light chain-1), and also tetanus toxoid. We also studied the responses of CD8+ T lymphocytes to these IDDM-relevant and -irrelevant antigens in Hashimoto's thyroiditis patients (HT), rheumatoid arthritis patients (RA), and normal control subjects (N) to compare the pattern of responses in the other autoimmune diseases. Activation of lymphocytes was monitored by measuring the expression of the activation molecule-major histocompatibility complex class II antigen (HLA-DR) on the surfaces of CD8+ T lymphocytes by flow cytometry. Peripheral blood mononuclear cells (PBMC) obtained from 14 patients with IDDM, 14 N, 14 with HT, and 13 with RA were cultured for 7 days in the presense or absence of antigens. The stimulation index (SI) of activation of the lymphocytes was determined. When the response of CD8+ T lymphocytes of IDDM patients to each of the IDDM-relevant antigens was compared to that of the irrelevant antigen, only GAD65 and ABBOS showed a significantly reduced activation compared to P348 and tetanus toxoid. Other relevant antigens, insulin, P69, and Tep69, did not show any significant differences in their SI compared to those of the irrelevant antigens. In the N, HT, and RA groups, there was no significant difference in the SI of the responses of CD8+ cells to any of the relevant antigens compared to that of the irrelevant antigens. Moreover, CD8+ T lymphocytes of IDDM patients showed a significantly lower activation by GAD65 than those from N, HT, and RA. In conclusion, our data suggest that CD8+ T lymphocytes of IDDM patients but not those from N, HT, and RA groups have specifically reduced potential for activation in response to GAD65 but not to insulin, P69, and Tep69, whereas ABBOS exerts a less well-defined reductive effect on the activation of CD8+ lymphocytes of IDDM patients. Since CD8+ cells have been shown to contain suppressor activity, our data support the notion that a disease-specific defect in GAD65 autoantigenic induction of suppressor T lymphocytes may be important in the pathogenesis of IDDM.

Insulin-Dependent Diabetes Mellitus: Islet Changes in Relation to Etiology and Pathogenesis

Type and type II diabetes are the most common types of diabetes. The ratio of type I to type II diabetes is about 1:9. Type I diabetes is caused by absolute insulin deficiency and is therefore referred to as insulin-dependent diabetes. The disease becomes manifest clinically in childhood or adolescence ("juvenile diabetes"), though onset in adulthood is increasingly being observed. Morphologically a subtotal (>80%) to total loss of B-cells in the pancreatic islets occurs. Lymphocytic insulitis, which disappears after the B-cells have been totally destroyed, is pathogneumonic of type I diabetes. This insulitis is an expression of an autoimmune event that is triggered by a multitude of factors. An important factor appears to be a genetic predisposition (human leukocyte antigen [HLA] DR3/DR4/DQ8) in connection with as-yet-unknown environmental factors (e.g., viruses). Autoantibodies, such as islet cell cytoplasmic antibodies (ICA). insulin autoantibodies (IAA) and/or autoantibodies to the gamma-aminobutyric acid (GABA)-synthesizing enzyme glutamic acid carboxylase (GAD), are already detectable in a prediabetic phase, though it is not possible to predict the time of clinical onset. The course of the disease is dependent on age. Young children require insulin therapy sooner than juveniles or adults.

Cell-mediated immune response to beta casein in recent-onset insulin-dependent diabetes: implications for disease pathogenesis

BACKGROUND

The cows' milk hypothesis for the cause of insulin-dependent diabetes (IDDM) is based on the concept that early consumption of cows' milk may expose the immune system to a foreign protein possessing immunological cross-reactivity with an antigen present on pancreatic beta-cells.

METHODS

We measured in-vitro peripheral lymphocyte response to beta casein, a protein in cows' milk, in 47 patients with recent-onset IDDM, in 36 healthy people and, to test disease specificity, in 10 patients with autoimmune thyroid disease. Other antigens tested for were bovine serum albumin, purified protein derivative, human serum albumin, and phytohaemagglutinin.

RESULTS

Specific proliferation of T lymphocytes with bovine beta casein was seen in patients with IDDM (mean [SD] age 18.7 [9]) with a significant difference in mean stimulation index (SI) versus healthy people (p < 0.00001) or patients with autoimmune thyroid disease (p < 0.002). 24 of 47 (51.1%) patients with IDDM versus 0/10 patients with thyroid disease and 1/36 (2.7%) healthy people had a positive response to beta casein defined as a SI above the mean value +2 SD of healthy people (p < 0.00001). No significant differences were observed between the groups of subjects with respect to other antigens tested.

INTERPRETATION

The association between IDDM and early consumption of cows' milk may be explained by the generation of a specific immune response to beta casein. Exposure to cows' milk triggers a cellular and humoral anti-beta casein immune response which may cross-react with a beta-cell antigen. It is of interest that sequence homologies exist between beta casein and several beta-cell molecules.

Prevention of IDDM: the genetic epidemiologic perspective

Rational prevention of insulin-dependent diabetes mellitus (IDDM) requires knowledge about the aetiology and pathogenesis of the disease. The causation of IDDM is complex, involving genetic susceptibility as well as non-genetic determinants. The evidence of a genetic component to IDDM is based on the high concordance rate in monozygotic twins as compared with dizygotic twins, the higher recurrence risk among relatives of patients with IDDM as compared with the general population risk, and the well-established associations with genetic markers, including specific alleles from the HLA-locus. The evidence of a non-genetic component to IDDM is primarily based on the fact that the concordance rate in monozygotic twins is far from unity; the huge geographical variation in the incidence of IDDM, even between genetically similar populations, and the increasing incidence in many populations provide further support; associations between the risk of developing IDDM and exposure to several non-genetic determinants, including nutrients and viral infections, have been established and serve as additional evidence. In general, the relative risks conferred by the non-genetic determinants are rather small, and it is unknown how these factors initiate the autoimmune-mediated process that destroys the beta-cells of the pancreas. Recent findings suggest that non-genetic factors interact with genetic susceptibility genes in the causation of IDDM. Firstly, it appears that the increase in the incidence of IDDM has predominantly been observed in populations with high frequency of susceptibility genes. Secondly, it seems that the risk of IDDM among relatives of patients with IDDM is positively correlated with the general population risk level. All these lines of evidence considered together suggest that IDDM may develop from several different combinations of susceptibility genes acting together with non-genetic exposures. If so, prevention of IDDM will require assessment of disease risk at individual rather than at population level. Since genetic screening is neither feasible nor ethically acceptable in the population at large, possible prevention of IDDM will be restricted to individuals who, by means of a positive family history, may be classified as being at high disease risk.

Islet cell and glutamic acid decarboxylase antibodies and heat-shock protein 65 responses in children with newly diagnosed insulin-dependent diabetes mellitus

Islet cell antibodies (ICA) were detected in 66% and glutamic acid decarboxylase (GAD) antibodies in 64% of children (n = 47) with newly diagnosed insulin-dependent diabetes mellitus (IDDM). Fifteen percent of the patients had neither GAD nor ICA antibodies. Responses to mycobacterial heat-shock protein 65 (Hsp65) were detected in all patients. There was a significant correlation between anti-GAD antibodies and proliferation of peripheral blood mononuclear cells to Hsp65, and between ICA and antibodies to Hsp65.

IgA bovine serum albumin antibodies are increased in newly diagnosed patients with insulin-dependent diabetes mellitus, but the increase is not an independent risk factor for diabetes

We studied the significance of antibodies to bovine serum albumin (BSA) as a risk factor for insulin-dependent diabetes mellitus (IDDM) in a case-control setting. IgA and IgG antibodies to BSA and ovalbumin were measured from sera of 104 patients with newly diagnosed IDDM and of 111 matched controls by enzyme-linked immunosorbent assay. Patients with diabetes had significantly higher levels of IgA antibodies to BSA (p = 0.003); IgG antibodies also tended to be higher (p = 0.08). Levels of IgA antibodies to ovalbumin were similar in the patients and controls, but IgG antibodies were higher in controls (p = 0.02). When antibodies to BSA, beta-lactoglobulin, whole cow's milk and islet cell antibodies were studied as risk determinants of IDDM in a multivariate, logistic regression analysis, IgA antibodies to beta-lactoglobulin and to cow's milk were independently associated with the risk (p = 0.037 and 0.048, respectively), while antibodies to BSA were not a significant risk factor. The results question the role of BSA as a cross-reacting antigen with pancreatic beta-cell surface proteins in the aetiology of IDDM.

Raising the pH of the pepsin-catalysed hydrolysis of bovine whey proteins increases the antigenicity of the hydrolysates

BACKGROUND

Hypersensitivity to cow milk protein is frequently observed in infancy. Since the pH in the infant's stomach is relatively high (pH 3-4) compared with adults (pH 2), an incomplete digestion of the milk proteins is expected to occur.

OBJECTIVE

The determination of the degree of hydrolysis by pepsin of the four main proteins of bovine whey, i.e. alpha-lactalbumin (alpha La), beta-lactoglobulin (beta Lg), bovine serum albumin (BSA) and bovine immunoglobulin G (B-IgG), in the pH range 2.0-4.0 and of the antigenic properties of the resulting hydrolysates.

METHODS

Whey proteins were successively hydrolysed with pepsin at pH values ranging from 2.0 to 4.0 and with pancreatic enzymes at pH 7.5 using a pH-stat. The resulting hydrolysates were characterized by their degree of hydrolysis, and analysed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, gel permeation chromatography and immunologically by competitive enzyme-linked immunosorbent assay.

RESULTS

In general, the degree of hydrolysis, the gel electrophoretic patterns, the contents of peptides of molecular mass > 5 kDa and the residual human-immunoglobulin E and G antigenicities of the hydrolysates did not differ much whether the pepsin incubation was done at pH 2.0 or 3.0. Pepsin incubation at pH 4.0, however, resulted in a decreased hydrolysis and enhanced residual antigenicity of alpha La, BSA and B-IgG, but not of beta Lg.

CONCLUSION

The poor and slow degradation of the antigenic epitopes of whey proteins when pepsin digestion occurs under conditions that prevail in the stomach of infants could be of much importance for the development of cow milk hypersensitivity. The immature gastrointestinal mucosal barrier of infants allows large antigenic fragments of these proteins to pass into the systemic circulation.

Molecular genetics of diabetes mellitus

As a result of advances in technology, genome searches have been carried out for susceptibility genes for type 1 diabetes in humans and in the NOD mouse. These have shown that, in the NOD mouse, diabetes susceptibility is under the control of at least ten separate chromosomal loci. In the human, in addition to HLA and INS, two new susceptibility genes have been localized, IDDM4 on chromosome 11q and IDDM5 on 6q, demonstrating the polygenic nature of type 1 diabetes and the role of HLA as the major locus. Candidate genes at these loci are the subject of current investigation. Genetic and immunological markers of disease may be of value in screening the general population for individuals at risk of developing type 1 diabetes. The predictive power of different screening strategies should be tested in order to work out the potential value to the general population of preventive therapies that are now undergoing clinical trials in high risk 'pre-diabetics'. Type 2 diabetes is genetically heterogeneous, and, since 1992, two distinct genetic subtypes have been identified. The first is defined by mutations in the GCK gene, which cause up to 60% of cases of MODY. The second, designated MIDD (maternally inherited diabetes and deafness), is defined by mutation in the mitochondrial gene for tRNA(Leu(UUR)). MIDD patients are less obese than is usual for typical type 2 diabetes, may present in early adult life or occasionally in childhood and may have been diagnosed as having autoimmune type 1 diabetes, type 2 diabetes or MODY. Typically, patients with MIDD require insulin earlier than do type 2 diabetics without mitochondrial mutations. Genetically complex diseases, such as diabetes, hypertension, cancer and coronary heart disease, are common in most populations. The approaches to the genetic analysis of diabetes outlined in this review are likely to be useful to the genetic analysis of many of these disorders. Progress in this area will have important implications for public health strategies in the next decade and beyond.

Antibodies to the Cryptococcus neoformans capsular glucuronoxylomannan are ubiquitous in serum from HIV+ and HIV- individuals

Murine MoAbs to the Cryptococcus neoformans capsular glucuronoxylomannan (GXM) polysaccharide are protective in mice in vivo and in vitro. The prevalence of protective anti-GXM antibodies in human serum is unknown. To provide further insight into the human antibody response to C. neoformans we determined the prevalence, isotype, and IgG subclass utilization of human anti-GXM antibodies in HIV+ and HIV- sera by a sensitive antigen capture FLISA assay. One hundred and twenty-three sera from the Bronx Municipal Hospital Centre serum bank were studied retrospectively. Seventy were from HIV+ individuals, 10 with a history of cryptococcal meningitis (CM), and 53 were from HIV- individuals. Serum GXM determinations were also performed on 61 HIV+ sera. Our results demonstrated that anti-GXM IgG, IgA, and IgM are ubiquitous in both HIV+ (including those with CM), and HIV- sera. Anti-GXM IgA titres and total serum IgA concentration were elevated in HIV+ sera. Anti-GXM IgG antibodies were almost exclusively isotype-restricted to the IgG2 subclass. Our data also demonstrated elevations of anti-bovine serum albumin (BSA) titres in HIV+ sera. Taken together, our findings confirm hypergammaglobulinaemia and expansion of anti-protein (BSA) antibodies in HIV+ individuals and isotype restriction of human anti-carbohydrate (GXM) antibodies to the IgG2 subclass. Our report of ubiquitous anti-GXM antibodies of the IgG and IgA isotypes suggests that anti-GXM antibodies exist before HIV infection.

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.

Self and non-self antigen in diabetic autoimmunity: molecules and mechanisms

In this article, we have summarized current facts, models and views of the autoimmunity that leads to destruction of insulin-producing beta-cells and consequent Type 1 (insulin-dependent) diabetes mellitus. The presence of strong susceptibility and resistance gene loci distinguishes this condition from other autoimmune disorders, but environmental disease factors must conspire to produce disease. The mapping of most of the genetic risk (or disease resistance) to specific alleles in the major histocompatibility locus (MHC class II) has direct functional implications for our understanding of autoimmunity in diabetes and directly implies that presentation of a likely narrow set of peptides is critical to the development of diabetic autoimmunity. While many core scientific questions remain to be answered, current insight into the disease process is beginning to have direct clinical impact with concerted efforts towards disease prevention or intervention by immunological means. In this process, identification of the critical antigenic epitopes recognized by diabetes-associated T cells has achieved highest priority.

T cell proliferative responses to glutamic acid decarboxylase-65 in IDDM are negatively associated with HLA DR3/4

Based on studies in spontaneously non-obese diabetic (NOD) mice, it has been suggested that the Mr 65,000 isoform of glutamic acid decarboxylase (GAD65) is of major importance in the pathogenesis of insulin-dependent diabetes mellitus (IDDM). In humans, antibodies to GAD65 are present before and at onset of the disease and in vitro T cell reactivity to GAD has also been reported. To further characterize the T cell recognition of GAD65, we incubated peripheral blood mononuclear cells from 45 newly diagnosed IDDM patients with purified recombinant human islet GAD65 and correlated the proliferative response with HLA DR haplotype and the presence of GAD65 autoantibodies. Fifty healthy individuals were studied as controls. Of the patients, 49% showed proliferative responses to GAD65 in contrast to only 4% of the controls. T cell proliferation to GAD65 was significantly more frequent in patients not being HLA DR3/4 heterozygous (19/29, 66%) as compared to HLA DR3/4 heterozygous patients (3/16, 19%) (p < 0.01). The difference was most pronounced in females with 64% (9/14) of the HLA non-DR3/4 patients being positive compared to none (0/6) of the HLA DR3/4 patients (p < 0.05). The overall frequency of GAD65 autoantibodies was 71% (32/45) with a similar distribution between patients with HLA DR3/4 (10/16, 63%) and HLA non-DR 3/4 (22/29, 76%). There was no correlation between levels of the T and B cell responses to GAD65 (r = 0.24). In conclusion, we find a proliferative T cell response to GAD65 in approximately 50% of recent onset IDDM patients and unexpectedly find the majority of responders to be HLA non-DR 3/4 heterozygous patients. No difference was observed in B cell responsiveness between the two HLA groups.

T cells from children with IDDM are sensitized to bovine serum albumin

Epidemiological and experimental evidence suggested that denial of dietary cow milk protein early in life protects genetically susceptible children and animals from insulin-dependent diabetes (IDDM). Bovine serum albumin (BSA) was proposed as a candidate milk-borne mimicry antigen responsible for the diabetogenic cow milk effect. Elevated anti-BSA antibodies have been observed in patients and diabetic rodents, and these antibodies precipitate p69 from islet cell lysates. IDDM is a T cell mediated disorder but efforts to detect BSA-specific T cells in diabetic children have so far failed. We describe here a culture system which allowed the detection of BSA-specific T cells and we mapped this response to the ABBOS peptide (pre-BSA position 152-169) previously identified as a possible mimicry epitope. ABBOS-sensitized T cells were found in 28/31 children with recent onset IDDM but not in non-diabetic controls nor in children with SLE or JRA. T cell proliferative responses declined within the first few years of diabetes diagnosis. Although no effector cell role for BSA/ABBOS specific T lymphocytes has been demonstrated, the presence of BSA peptide-specific T cells strengthens the postulated link between a cow milk protein and IDDM.

Dietary factors in the aetiology of diabetes

Quite different nutrition-related environmental factors influence the development of type 1 insulin-dependent diabetes (IDDM) and type 2 non-insulin-dependent diabetes (NIDDM). IDDM is characterized by progressive beta-cell destruction which leads to complete insulin deficiency; at the time of diagnosis 80-90% of beta cells have been destroyed. In children there is epidemiological evidence that high intake of nitrites and N-nitroso compounds, early introduction of cow's milk to the diet and short duration or absence of breastfeeding increase the risk of IDDM. Studies in experimental animals suggest that cow's milk and soy proteins may be diabetogenic. There is current interest in the effects of free radical scavengers, particularly niacin and natural and synthetic antioxidants on the incidence of IDDM. These findings from ecological, animal, and human case-control studies remain to be evaluated in prospective cohort studies covering infancy and childhood and finally in human intervention trials. NIDDM is characterized by insulin resistance which is complicated by impaired insulin secretion at the time of appearance of hyperglycaemia and clinical diabetes. Its preclinical development is insidious and poorly defined, and there is little direct evidence that the same factors which influence metabolic control in clinical diabetes also affect the preclinical development of the disorder. Obesity, particularly of the abdominal type, is common in people who develop NIDDM, and weight control by appropriate diet and physical activity is probably the most important measure for preventing NIDDM. High (saturated) fat intake seems to be associated with insulin resistance, obesity and increased risk of NIDDM, and diets high in carbohydrate seem to protect from glucose intolerance and diabetes, mainly owing to their high fibre content.

No association between anti-bovine serum albumin antibodies and islet cell reactive antibodies in newly diagnosed type 1 diabetic patients

Serological findings have suggested that antibodies (Ab) to bovine serum albumin (BSA-Ab) are associated with type 1 diabetes mellitus. The aim of our study was to evaluate a competitive fluid-phase radioimmunoassay for detecting BSA-Ab using different incubation times and to study a possible association of these BSA-antibodies with autoantibodies (AAb) frequently detected in type 1 diabetic patients. For the overnight incubation time, there was an enormous overlap in the [125I]BSA binding by serum samples between 52 newly diagnosed type 1 diabetic patients (mean [125I]BSA binding 23.6 +/- 17.4%) and 54 healthy blood donors (mean [125I]BSA binding 10.2 +/- 15.7%). By an incubation time of only 3 min the BSA-antibody prevalence was found to be 15.4% (8/52) for type 1 diabetic patients and 3.7% (2/54) for control subjects. However, there was no association between BSA-Ab and type 1 diabetes-associated antibodies as cytoplasmic islet cell antibodies (ICA), or glutamate decarboxylase autoantibodies. Our results confirm that (i) BSA-Ab occur more frequently in newly diagnosed type 1 diabetic patients compared with a healthy control group and (ii) that the BSA-Ab detected by the fluid-phase radioimmunoassay with an incubation time of 3 min are more disease-associated than the [125I]BSA binding after an overnight incubation. The competitive BSA-Ab fluid-phase radioimmunoassay described is a simple and rapid method to detect antibodies specifically reactive with BSA. It is suggested that the humoral immune reactivity to BSA in type 1 diabetic patients probably reflects an unspecific defect of the immune system and gives no additionally diagnostic value about the type 1 diabetes.