Diabetes, Vol 47, Issue 1 32-38, Copyright © 1998 by American Diabetes Association
Paradoxical antidiabetogenic effect of gamma-interferon in DP-BB rats
F Nicoletti, P Zaccone, R Di Marco, G Magro, S Grasso, F Stivala, G Calori, L Mughini, PL Meroni and G Garotta
Institute of Microbiology, University of Milan, Italy. fnicol@herganet.it
Previous studies have shown that anti-gamma-interferon (IFN-gamma) antibody
reduces the frequency of autoimmune IDDM in the DP-BB rat. We tested the
effects of systemically administered recombinant rat IFN-gamma in both
DP-BB and DR-BB rats. Unexpectedly, IFN-gamma markedly reduced the
incidence of IDDM as compared with control rats when administered six times
per week at a dosage of 280,000 U between ages 30-35 to 105 days or ages
60-64 to 105 days. A lower dosage (28,000 U on alternate days) was also
protective when administered to DP-BB rats between birth and age 60 days.
However, long-lasting protection against IDDM development over the 1-year
study period was achieved only by the highest dosage of IFN-gamma
administered from age 30 to 105 days. Ex vivo production of tumor necrosis
factor-alpha from splenic lymphoid cells (SLCs) and peritoneal macrophages
of the rats treated with IFN-gamma was comparable with that of controls;
however, SLCs from the IFN-gamma-treated animals secreted lower amounts of
IFN-gamma after stimulation with concanavalin A. IFN-gamma treatment also
markedly reduced the frequency of phenotypically activated SLC-expressing
class II antigens and interleukin-2 receptor. Finally, in agreement with
the observed antidiabetogenic effects, exogenously administered IFN-gamma
induced neither insulitis nor IDDM development in DR-BB rats, a subline of
DP-BB rats in which autoimmune diabetes rarely occurs spontaneously but can
be induced by administration of polyinosinic-polycytidilic acid.