Diabetes, Vol 39, Issue 5 590-596, Copyright © 1990 by American Diabetes Association
Studies on autoimmunity for initiation of beta-cell destruction. V. Decrease of macrophage-dependent T lymphocytes and natural killer cytotoxicity in silica-treated BB rats
K Amano and JW Yoon
Julia McFarlane Diabetes Research Centre, Faculty of Medicine, University of Calgary, Alberta, Canada.
Administration of silica, which is selectively toxic to macrophages, to
young BB rats resulted in the prevention of insulitis and diabetes.
However, the mechanism leading to the prevention of an autoimmune process
in silica-treated BB rats is not known. This study was undertaken to
investigate the mechanism involved in prevention of insulitis and diabetes.
Neonates of diabetes-prone BB (DPBB) rats injected with concanavalin A
(ConA)-activated spleen cells from silica-treated DPBB (STDPBB) rats did
not develop insulitis or diabetes, whereas DPBB neonates injected with
ConA-activated spleen cells from the untreated DPBB rats developed both
insulitis and diabetes. Not only was there a decrease of natural killer
(NK) cell activity in splenocytes from STDPBB rats, but there was also a
significant reduction in the number of immunocytes such as T lymphocytes
(helper/inducer and cytotoxic/suppressor) and NK cells. The number of
macrophages in both spleen and peripheral blood was significantly decreased
in STDP rats compared with untreated DP rats. In contrast to the changes in
T lymphocytes and NK cell activity, there was no change in target
beta-cells in STDPBB rats with regard to the susceptibility to adoptive
transfer of insulitis. It is concluded that the prevention of insulitis and
diabetes in STDPBB rats is due to a decrease in macrophage-dependent T
lymphocytes and NK cell cytotoxicity.