Resistance and susceptibility to the induction of rat adjuvant disease. Diverging susceptibility and severity achieved by selective breeding.

Rats selected for their ability to develop or resist adjuvant disease were used to establish 2 inbred lines of rat over 20 generations. A resistant line was rapidly established with almost 100% non-responsiveness by the sixth generation. A line showing 100% susceptibility was also established very rapidly but throughout the course of the breeding programme the severity continued to increase in intensity to a level considerably above that to be seen in strains normally considered to be high responders. At the thirteenth generation and beyond, the susceptible line showed a marked sex difference in the secondary lesions, females being more severely affected than the males. The 2 lines of rat were also tested for their ability to develop experimental allergic encephalomyelitis (EAE) in selected generations. There was no clear correlation between the 2 diseases although those animals developing the most severe adjuvant disease also had the most severe EAE.