Increased levels of circulating immune complexes are not associated with diabetes in BB rats
Summary, in English
Increased levels of circulating immune complexes (IC) have been described in insulin-dependent diabetic (IDD) patients at the time of diagnosis. The aim of the present study was to test whether the spontaneously diabetic BB rat had changes in IC levels at different ages prior to and at onset of IDDM as compared with diabetes resistant BB rats and normal Wistar Furth rats. The IC levels were related to serum IgG concentration as well as to total peripheral blood lymphocyte counts. Three groups of rats with 12 animals in each were followed: Diabetes-prone, lymphopenic (DP) BB rats with an expected high incidence of diabetes, diabetes-resistant (DR) BB rats from the non-diabetic w-subline, and Wistar Furth rats. Blood samples collected on 12, 22, 29, 43, 71, and 99 days of age were analyzed for IC, detected in a solid phase of C1q assay, serum IgG levels, and peripheral blood lymphocytes. Diabetes developed in 8/12 (66%) DP BB rats between 70 and 93 days of age while none of the DR BB rats developed diabetes. The levels of IC tended to increase with age in all three groups of rats and did not differ between DP BB and Wistar rats whereas DR BB rats had significantly higher levels (p < 0.05-0.01) at all ages. The profile of serum IgG was similar in all rats showing a high level at 12 days of age and a nadir at day 29 followed by an increase from day 43 until the end of the follow-up period. The Wistar rats had significantly higher IgG levels (p < 0.05-0.001) from day 22 to day 99 when compared to either DP BB or to DR BB rats. Only minor differences were found in serum IgG levels between DP BB and DR BB rats. There was no correlation between the levels of IC and IgG. Moreover, there was no difference in neither IC nor IgG levels between the eight diabetic and the four DP rats which remained non diabetic. The DP BB rats were lymphopenic already at 12 days of age and the lymphopenia persisted throughout the study period. The lymphocyte counts showed a weak correlation with the IC levels in all three groups of rats. It is proposed that DP BB rats may have an inability to form C1q positive IC which could reflect their propensity to develop organ-specific autoimmunity.
- ISSN: 0265-5985