A prospective analysis of islet-cell cytotoxic antibodies in insulin-dependent diabetic children. Transient effects of plasmapheresis

GAD-alum immunotherapy in Type 1 diabetes mellitus

Glutamic acid decarboxylase (GAD)-alum (Diamyd®, Diamyd Medical, Stockholm, Sweden) is an adjuvant-formulated vaccine incorporating recombinant human GAD65, the specific isoform of GAD expressed in human pancreatic β-cells and a major antigen targeted by autoreactive T lymphocytes in Type 1 diabetes mellitus. Intermittent vaccination with this protein is theorized to induce immune tolerance to GAD65, thereby potentially interrupting further β-cell destruction. Hence, clinical trials are ongoing to examine the efficacy and safety of GAD-alum immunotherapy in patients with autoimmune-mediated forms of diabetes, including Type 1 diabetes and latent autoimmune diabetes in adults.

Molecular mimicry, bystander activation, or viral persistence: infections and autoimmune disease

Virus infections and autoimmune disease have long been linked. These infections often precede the occurrence of inflammation in the target organ. Several mechanisms often used to explain the association of autoimmunity and virus infection are molecular mimicry, bystander activation (with or without epitope spreading), and viral persistence. These mechanisms have been used separately or in various combinations to account for the immunopathology observed at the site of infection and/or sites of autoimmune disease, such as the brain, heart, and pancreas. These mechanisms are discussed in the context of multiple sclerosis, myocarditis, and diabetes, three immune-medicated diseases often linked with virus infections.

Flow injection fluorescence microscopy applied to a rapid cell surface immunoassay

A perfusion system for fluorescence microscopy that utilized a flow injection system was developed and used to study cell surface antibody binding on viable cells grown in monolayer cultures on coverslips. A polyclonal cell-specific antiserum used to probe the cell surface was monitored by indirect immunofluorescence. The flow injection system was completely automatic and allowed controlled perfusion of cell surfaces with the desired sequence of antibodies. The individual steps of the indirect assay were studied to determine the binding behavior of the primary cell surface antibody, the labeled second antibody, and control of nonspecific binding. Under stopped flow conditions, the second antibody was maximally bound within 10 min, while constant mixing of the second antibody solution over the cells resulted in maximal binding within as little as 6 min. A primary antibody contact time of 2 min followed by a wash and then exposure to the second antibody for 2 min showed that this fast automated procedure could distinguish specific from nonspecific binding of cell surface antibodies to the same set of cells for several repeated exposures. The flow injection fluorescence microscopy system can be automated to allow screening for cell surface antibodies and to study their interaction with specific cell surface antigens.

Complement-dependent antibody-mediated cytotoxicity in the spontaneously diabetic BB/OK rat: association with beta cell volume density

The present study examined in the spontaneously diabetic BB/OK rat whether a relationship exists between the appearance of complement-dependent antibody-mediated cytotoxicity (C'AMC) in serum and the relative beta cell volume density determined in pancreatic biopsies. C'AMC was estimated by 51Cr release from prelabeled major histocompatibility complex-compatible neonatal rat islet cells after exposure to rat serum and rabbit complement. Fifty-one percent (72/141) of sera from BB/OK rats with newly diagnosed diabetes were positive for C'AMC. At onset of hyperglycemia, insulin-immunoreactive beta cells were only detectable in pancreas biopsies of 25% (10/40) of the BB/OK rats who displayed mild hyperglycemia (plasma glucose 8.3-13.0 mmol/l) and low serum C'AMC. A twofold increase (p less than 0.01) of C'AMC and loss of the remaining beta cells was evident in untreated animals upon their reexamination within 1 week after diagnosis of hyperglycemia. Initiation of insulin therapy prevented neither the increase in C'AMC activity nor the decrease in the beta cell volume density. In contrast, three out of four mildly hyperglycemic BB/OK rats treated with cyclosporin A maintained both their initial C'AMC levels and relative beta cell volume density not only throughout the treatment period (4 weeks) but also for at least 4 weeks thereafter. In one additional animal receiving cyclosporin A no protection of the remaining beta cells could be achieved and C'AMC levels were markedly increased. It is concluded that the appearance of increased C'AMC in serum may reflect autoimmune reactions against the islet beta cells of spontaneously diabetic BB/OK rats. The increase of C'AMC seen in untreated as well as insulin-treated BB/OK rats, which were even devoid of beta cells, suggests that C'AMC activity appears secondary to the loss of beta cells. These results do not support the hypothesis of a direct beta cell destruction via intrainsular complement activation.

Presence of complement-dependent cytotoxic activity against clonally-derived rat islet tumour cells in sera from type 1 (insulin-dependent) diabetic patients and control subjects

Heat-inactivated sera from newly diagnosed Type 1 (insulin-dependent) diabetic patients and control subjects were tested for the presence of antibodies to islet cell surface antigens by means of a sensitive immunofluorescent, microcytotoxicity assay using two clones of a rat islet cell tumour as antigens. Complement-dependent cytotoxicity was found in 74% of diabetic patient sera and 87% of control sera, and there were no significant differences in titres between diabetic patients and control subjects. A minority of the sera from both patients and controls were cytotoxic for only one of the two clones, suggesting the presence of multiple antigen-antibody systems. Preadsorptions of the sera with rat liver powder, sheep erythrocytes, and/or protein A-conjugated agarose beads were inconsistently effective in decreasing levels of lytic activity in control sera. It is concluded that more information is required concerning the antigens of rat islet cells and islet cell cytotoxic factors present in normal sera before such cells and assays can be reliably used for the detection of islet cell surface antibodies.

Onset of type I diabetes mellitus, hypothyroidism, and hypogonadism on withdrawal of glucocorticoid therapy and remission on its resumption in a patient with rheumatoid arthritis

A 57-year-old white man manifested adrenal insufficiency, insulin-dependent diabetes mellitus reflected by diabetic ketosis, primary hypothyroidism, and primary hypogonadism on rapid withdrawal of glucocorticoid therapy of several years' duration for rheumatoid arthritis. Resumption and continuation of glucocorticoid therapy for six months resulted in remission of type I diabetes mellitus and hypogonadism, and a euthyroid state was achieved by replacement therapy with L-thyroxine.

Increased reduction in fasting C-peptide is associated with islet cell antibodies in type 1 (insulin-dependent) diabetic patients

A cohort of 82 patients with Type 1 (insulin-dependent) diabetes was followed prospectively for 24 months, and 54 of them for 30 months, to study the relationship between fasting levels of immunoreactive C-peptide and titres of islet cell antibodies. After diagnosis, fasting C-peptide rose temporarily for 1-6 months of insulin therapy and declined continuously thereafter. While islet cell antibodies were present among 55% of the newly diagnosed patients, only 31% remained positive at 30 months. Their antibody titres decreased from 1:81 at diagnosis to 1:3. Only 3 patients (4%) who were islet cell antibody negative at diagnosis became positive later. The median C-peptide values among the persistently islet cell antibody positive patients decreased from 0.11 pmol/ml at 18 months, to 0.09 pmol/ml at 24 months, to 0.06 pmol/ml at 30 months compared to 0.18 (p = 0.04), 0.15 (p = 0.05) and 0.16 (p less than 0.003) pmol/ml, respectively, for the islet cell antibody negative patients. The median slope for the latter was -0.09 compared to -0.19 for the islet cell antibody positive patients (p = 0.01). These differences were reflected in increasing dosages of insulin, since patients remaining antibody-positive for 30 months were given 1.3-1.4 times more insulin (p = 0.01-0.004) than the antibody negative patients. This study demonstrates that islet cell antibodies may be a useful marker for predicting an increased rate by which endogenous B cell function is lost in Type 1 diabetes.