Karsten Buschard

Antigen expression of the pancreatic beta‐cells is dependent on their functional state, as shown by a specific, BB rat monoclonal autoantibody IC2

Antigen expression is studied corresponding to a monoclonal autoantibody (IC2) derived from a hybridoma of rat myeloma Y3 cells and splenocytes of the diabetic BB rat. The selective reactivity of IC2 with islet cells has earlier been proven. We studied the possible specificity for beta islet cells, and the possible variation in autoantigen expression. Islet cells were isolated by cautious collagenase and dispase treatment. The cells were labelled with IC2 alone or together with anti‐insulin immunoglobulin in double‐labelling experiments. Extensive series of cells were examined by immunofluorescence microscopy, and some samples also by flow cytometry. In double‐labelling examinations we found that only anti‐insulin positive cells could bind the IC2 antibody, thus showing beta‐cell selectivity. On the other hand, not all anti‐insulin positive cells were IC2‐positive. Since insulin treatment has been shown to decrease the incidence of diabetes in the BB rat, islet cells were examined after reduced beta‐cell strain. Islet cells from Lewis and Wistar Furth rats display 21.4 ± 1.4% IC2‐positive cells, while islet cells from 24‐hour fasting animals showed 7.0 ± 1.4% (p < 0.0001). Similar results were seen for BALB/c mice (25.0 ± 1.8% vs. 13.7 ± 2.3%, p < 0.002). Also, after a week of insulin treatment, autoantigen expression was significantly decreased. Thus, the IC2 antibody is beta‐cell‐specific, and expression of the corresponding cell surface antigen depends on the functional state of the beta‐cells.

T lymphocyte subsets in patients with newly diagnosed type 1 (insulin-dependent) diabetes: a prospective study

SummaryT lymphocyte subsets in peripheral blood from 11 newly diagnosed Type 1 (insulin-dependent) diabetic patients were studied prospectively at three time intervals: as soon as possible after diagnosis, 3 weeks and 5 months later. Lymphocytes were marked with monoclonal OKT antibodies and examined in a fluorescence-activated cell sorter. The percentage of T lymphocytes (OKT 3) did not change significantly at the three study times. The percentage of helper/inducer T cells (OKT 4) was high the first week after diagnosis, but decreased at the 5-month examination (p<0.05). The percentage of suppressor/cytotoxic T cells (OKT 8) was low at diagnosis but increased at 3 weeks (p<0.02) and 5 months (p<0.01). The ratio OKT4/OKT8 lymphocytes was 2.28 at diagnosis, decreasing to 1.77 at 3 weeks and 1.87 at 5 months, compared with 1.46 for 16 age-matched control subjects. There was no significant change in the absolute number of lymphocytes. It is concluded that the distribution of T cell subsets was abnormal at the time of diagnosis, but changed towards normal within a few weeks, after which there was no significant change at 5 months. It is as yet unknown whether the high proportion of helper/inducer T cells and/or the low percentage of suppressor/cytotoxic T cells at diagnosis favour immune reactions involved in the pathogenesis of Type 1 diabetes.

What causes type 1 diabetes? Lessons from animal models

Buschard K. What causes type 1 diabetes? Lessons from animal models. APMIS 2011; 119 (Suppl. 132): 1–19

PASSIVE TRANSFER OF DIABETES MELLITUS FROM MAN TO MOUSE

Lymphocytes extracted from peripheral-blood samples from each of six patients with newly diagnosed insulin-dependent diabetes mellitus were transplanted into arthymic nude mice. At one or more sampling times (in the thirty-day study) blood sugar was higher in mice which had received lymphocytes from diabetic patients than in the control mice which had received lymphocytes from non-diabetic donors. Blood-sugar concentrations reached 260 mg/dl in some mice in the experimental group. This study demonstrates that lymphocytes may have an aggressive role in diabetogenesis. With this mouse experimental model mechanisms involved in diabetogenesis, and probably also in other disease in which lymphocytes are suspected of being involved in pathogenesis, could be investigated.

Type 1 (insulin-dependent) diabetes mellitus diagnosed during pregnancy: a clinical and prognostic study

SummaryThe study concerns the clinical outcome and later prognosis (regarding permanent insulin treatment) of patients who develop insulin-dependent diabetes mellitus during pregnancy (which is different from gestational diabetes). Sixty-three such patients (27±1 (SEM) years old) were delivered at the Copenhagen Centre for Diabetes and Pregnancy during the years 1966–1980. Obstetric complications such as toxaemia were seen in 9.5% of these study patients and the perinatal mortality was 6.3%, both percentages being higher than in the general population (1.1%,p<10−7 and 1.0%,p<10−3, respectively), but similar to those observed in patients with Type 1 diabetes diagnosed before pregnancy. In contrast, the frequency of malformations was 1.6%, the same as in the general population (1.4%), but lowerthan that seen in patients with long-standing diabetes (8.3%,p<0.05). At follow-up examination 8±1 years after diagnosis all patients were diabetic; 77% were insulin treated, having no or virtually no residual B-cell function, and were clearly Type 1 diabetic patients. After delivery 80% of the patients had a remission period (median 256 days) without insulin treatment. This remission period was absent or shortest in patients with the following characteristics (p≤0.03): low age, first parity, not overweight, and high blood glucose level at diagnosis. These prognostic parameters should be considered in obligatory, clinical follow-up plans for such patients.

INVESTIGATIONS IN CHILDREN WHO WERE IN UTERO AT ONSET OF INSULIN-DEPENDENT DIABETES IN THEIR MOTHERS

55 children who were in utero when type 1 diabetes developed in their mothers were studied at a mean (SEM) age of 10.4 (0.6) years: only 1 was diabetic. Biochemical and immunological indices, measured in 35 children, showed no evidence of beta cell dysfunction. Thus, the fetal beta cells seem to be unaffected by the mechanisms that cause diabetes in their mothers.

Prevention of type 1 diabetes by inducing subclinical dermatitis on a small area.

We have previously epidemiologically shown that type 1 diabetes is inversely associated with contact allergy. This finding is intriguing as type 1 diabetes and contact allergy are two completely different diseases, although T cells are involved in both diseases. The objective of this study was therefore to experimentally study the effect of contact allergens on the development of diabetes in non‐obese diabetic mice.