Occurrence of antibodies against gene products of the major histocompatibility complex in normal sera of diabetes-prone BB rats.

Natural antibodies were detected in normal sera of diabetes-prone rats of substrain dp BB/DK (19.5%), non-diabetes-prone ndp BB/PhiK (17.8%) and their ancestral randombred strain WOK (2.2-7.5%). These antibodies were haemagglutinins specifically reacting with antigenic products of the RT1.A region, mainly with products of RT1.Aa,d,f haplotypes. The possible causes of this unusual finding are discussed.