Species specificity in response to tryptophan modified encephalitogen

Diversity in response to a modified basic encephaltiogenic myelin protein between species has been demonstrated. The encephalitogen was modified with reagents speccific to tryptophan: 2-hydroxy-5-nitrobenzyl bromide (HNBBr), nitrophenylsulfenyl chloride (NPSCl), oxidationn by performic acid and treatment with formic acid saturated with HCl gas. The modified proteins were found to be non encephalitogenic in guinea pig. These experiments combined with other investigators' findings suggest that tryptophan is an essential amino acid for the encephalitogenic activity when guinea pig is used as test animal. This, however, does not necessarily apply to other species. The three preparations, HNB, NPS and formylated proteins, were fully active in rabbit. Furthermore, the HNB modified protein and the peptide of 45 amino acid residue which has no tryptophan were active also in monkey. The foregoing evidence suggests that the basic myelin protein contains more than one encephalitogenic site; therefore, in determining the activity stress should be laid on the recipient. Some species may recognize a second active peptide, which contains no tryptophan. The conclusion reached is that the recognition of particular encephalitogenic sequence depends on the animal used for the test.