Elevated serum placental isoferritin in newly diagnosed Type 1 (insulin-dependent) diabetes mellitus. A possible marker for identification of high risk subjects

Summary Placental isoferritin is produced by activated T lymphocytes and may, therefore, be considered as a manifestation of T cell involvement. Placental isoferritin is measured using CM-H-9 monoclonal antibody which binds exclusively to placental isoferritin. Placental isoferritin has been determined in the serum of 80 patients with Type I (insulin-dependent) diabetes mellitus, 100 healthy first degree relatives and 81 healthy children. Serum levels which were measured in Type 1 diabetic patients, (24,0–140 U/ml; median and range) were significantly higher than those of family members (0,0–73; median and range; p<0.0001) and normal control subjects (0,0–48; median and range; p<0.0001). Using 0–10 U/ml as the upper limit of normal, it was found that 31 of 50 (62%) of Type 1 diabetic patients, 25 of 100 (25%) family members and 7 of 81 (8.6%) healthy control subjects had abnormal placental isoferritin levels. Islet cell antibodies were positive in 31 of 44 tested diabetic patients and, in 8 of 71 tested family members, and among them 54.8% and 50% respectively also had elevated placental isoferritin levels. However, no statistically significant correlation was found between islet cell antibodies and placental isoferritin levels. Treatment of Type 1 diabetic patients with insulin was accompanied by a significant decrease (p<0.002) of serum placental isoferritin within 2–4 weeks of treatment. It is noteworthy that placental isoferritin was below detection in 34 of 35 Type 2 (non-insulin-dependent) diabetic patients. Our findings suggest that placental isoferritin may be a marker of T cell involvement in autoimmune diabetes and that it could be used to identify high risk healthy first degree relatives.