Anti-islet immunity was studied in six spontaneously insulin-dependent diabetic (IDD) dogs, using mouse islets of Langerhans cells as targets, in vitro. Insulinopenia was demonstrated in all dogs by an i.v. glucose tolerance test. A significant lymphocytopenia was detected in the peripheral blood of this diabetic group. Pancreatic tissue from one of these animals was obtained shortly after death and the islets displayed a marked loss in beta cells without significant changes in the other types of islet cells. No insulitis was observed.
Circulating mononuclear cells from the diabetic dogs induced an increased basal insulin (IRI) release from islet cells and a suppressed stimulated IRI release. Damage to or depth of beta cells may account for these findings.
The stimulated IRI release was also suppressed when islets were incubated with the diabetic sera + complement, while the D-cell response to arginine was not altered, and the A-cell response was reduced but not abolished. A lysis of islet cells in the presence of IDD sera + complement was demonstrated by an increased release of 51Cr from labeled cells. These anomalies were observed neither when complement was heat-inactivated nor in the presence of control sera + complement.
Canine IDD may be a new animal model for the study of anti-islet cellular and humoral immunities.