Summary
Sera were obtained from 24 patients with newly-diagnosed insulin-dependent diabetes
mellitus (IDDM) and 14 children with a high risk of diabetes. The influence of the
decomplementated sera on basal and stimulated insulin secretion was studied in a mixed
culture of newborn rat islet cells. In addition, complement-dependent antibody-mediated
cytotoxicity (C'AMC) was measured by 51Cr-release from pre-labelled islet cells.
Incubation of the islet cells with sera from ten IDDM patients did not affect the
basal insulin release. Sera from other children with IDDM (n = 14) either significantly
increased (n = 7) or inhibited (n = 7) basal IRI secretion was compared with the sera
of control donors. Nearly half of the sera from the high-risk children was found to
be insulin-stimulating. Preincubation of islet cells with sera from IDDM children
caused a significant decrease of insulin response to 16.5 mM glucose plus 5 mM theophylline
(P < 0.001). Sera from the high-risk children did not influence the response of pancreatic
cells to secretagogues. C'AMC was found in 45% of the patients with IDDM and in 33%
of the high-risk children, however, there was no correlation between C'AMC and serum
effect upon basal insulin secretion.
These results suggest the presence of B-cytotropic factors in serum from children
with IDDM or with a risk of diabetes. Opposite effects of different sera on insulin
secretion may reflect the variety of pathogenetic mechanisms involved in islet cell
destruction.
Key Words
Insulin secretion - Islet cells - Complement-dependent antibody-mediated cytotoxicity
- Type I Diabetes Mellitus
