Diabetes, Vol 37, Issue 10 1411-1418, Copyright © 1988 by American Diabetes Association
IDDM in BB rats. Enhanced MHC class I heavy-chain gene expression in pancreatic islets
SJ Ono, B Issa-Chergui, E Colle, RD Guttmann, TA Seemayer and A Fuks
McGill Cancer Centre, Department of Medicine, McGill University Faculty of Medicine, Montreal, Quebec, Canada.
Modulation in major histocompatibility complex (MHC) gene expression
correlates with the inflammatory reactions that occur during graft
rejection and autoimmune disease. We analyzed the expression of class I and
II MHC genes in the pancreatic islets of prediabetic and newly diabetic BB
rats by immunohistochemistry of tissue sections and Northern blotting of
RNA extracted from isolated islets. We show that enhanced levels of MHC
class I heavy-chain RNA are present in pancreatic islets before overt
inflammation and the onset of insulin-dependent diabetes mellitus (IDDM) in
the spontaneously diabetic BB rat. Immunohistochemical analysis revealed
enhanced class I antigen expression throughout the pancreatic islets of
newly diabetic animals but no induction of class II antigen on endocrine
cells within the islet. Varying degrees of inflammatory infiltrate were
observed in the sections exhibiting enhanced class I antigen expression or
in nearby serial sections. Southern blot analysis revealed no
restriction-fragment-length polymorphism or amplification of the endogenous
class I heavy-chain genes compared with those of seroidentical
disease-resistant Wistar-Furth rats. I-A alpha and I-E alpha hybridizing
RNA appeared de novo before overt diabetes, although concomitantly with
T-lymphocyte-receptor beta-chain and interferon-gamma gene hybridizing RNA
and after MHC class I heavy-chain RNA enhancement was observed. These data
indicate the possibility that enhanced class I heavy-chain gene expression
plays a role in the progression of IDDM.