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SummaryIntraperitoneal insulin infusion using implantable devices in insulin-dependent diabetic (IDDM) patients is promising since it improves diabetic control and decreases frequency of hypoglycaemia. However, preliminary data show a striking increase in plasma levels of anti-insulin antibodies with this therapy. In order to more precisely evaluate the immunogenicity and its consequences, anti-insulin antibody levels in 62 IDDM patients were assessed every 3 months during a 2-year period following pump implantation. At the same time, diabetes control was evaluated with HbA~c , mean blood glucose levels, standard deviation of the daily blood glucose levels and the frequency of low blood glucose (< 3.58 mmol/1). Factors involved in antibody formation such as age, gender, HLA typing, and complement C4 alleles were also studied. After implantation, anti-insulin antibody levels increased significantly from 3.14 % (range 0-26 %) to 8.34 % (0-49 %) after 1 year and remained elevated. Patients were divided into two groups: responders able to show at least one antiinsulin antibody titre higher than 15 % and non-responders whose titres were always lower than 6 %. None of the factors studied was shown to statistically influence the anti-insulin antibody titres. Non-respouders had significantly better metabolic results than the responders. Severe hypoglycaemic episodes decreased dramatically in both groups. Insulin requirements were comparable at time 0 and decreased initially in both groups. They remained low for the non-responders but returned to pre-implantation values for responders. Intraperitoneal insulin infusion led to a high immunogenetic response towards insulin in about half of the patients, leading to only moderately deleterious effects on metabolic control. Further studies are necessary to document other consequences (such as the role of circulating immune complexes). [Diabetologia (1995) que mainly due to the improvement in quality of life. The first results of efficacy studies are encouraging [3] since they demonstrate a drastic reduction in the incidence of severe hypoglycaemic episodes when compared to subcutaneous insulin administration [2,4]. However, preliminary data from our group and from others have shown a striking increase in anti-insulin antibody levels (AIA) in plasma during longterm i.p. insulin infusion using implanted devices [5][6][7][8][9]. The aim of this study was to evaluate more precisely the immunogenicity of this new method of treatment, to define the different factors involved and to assess the eventual clinical and metabolic consequences of this immune reaction.

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