A comparative study of antigen expression by skin and pancreas in the prediabetic and diabetic state of the BB rat.

Type 1, insulin-dependent diabetes mellitus is an autoimmune disease with destruction of beta-cells in islets of Langerhans by activated (antigen-positive) infiltrating mononuclear cells accompanied by serological immune phenomena. The pathological mechanism has not yet been clarified in detail, and some inversion in the proportion of epidermal antigen expression has recently been described in spontaneous diabetes. The BB rat is one of the animal models most closely resembling human type 1 diabetes of autoimmune origin. We compared the class I and class II antigen expression in the islets of Langerhans and in the skin of spontaneously diabetic (BBD) and normoglycaemic (BBND) BB rats in the prediabetic, diabetic and non-diabetic states. Class I and class II antigen expression increased significantly in the islets of BBD rats from prediabetes to diabetes and compared with non-diabetic controls. In the same period, the dermal antigen expression (class I and class II) did not decrease and was not lower in BBD than in BBND animals. These results do not support a loss of activated (antigen-positive) dermal cells at the onset of diabetes in the BB rat and do not show a clear correlation with the antigen expression in infiltrated islets of Langerhans.