Age as a factor determining susceptibility for experimental autoimmune encephalomyelitis in the rat

The effect of age on the susceptibility to experimental autoimmune encephalitis was studied in different strains of rats and their hybrids. In the Brown-Norway (BN) strain no susceptibility was seen at any age. In the nearly resistant Fischer (F) strain, no change in clinical disease but an increase in histological scoring could be seen with increasing age. When hybrids between F and BN were studied, a clear-cut increase in clinical susceptibility was seen with age but no change in histological scores, while the F1 hybrid between BN and the susceptible Lewis strain showed no change in clinical susceptibility but an increase in histological scores with age. The findings are discussed together with previous data on these strains in terms of different mechanisms of resistance in the F and BN strains.