| Abstrakt: |
A1 proteins prepared from myelin of many animal species including human, monkey, bovine, rabbit, guinea pig, horse, sheep, dog, rat, chicken, and turtle were tested in the guinea pig for encephalitogenic activity. The mammalian A1 proteins were equally encephalitogenic producing marked clinical and histologic signs at 10 to 100 µg. The turtle A1 protein was inactive (100- to 1000-fold less active than the mammalian proteins). The chicken A1 protein, which was also much less active, failed to elicit clinical signs of experimental allergic encephalomyelitis but in 6 of 20 animals produced a small number of histologic lesions (perivascular cuffing of mononuclear cells). These results were correlated with the amino acid sequence in the tryptophan region of the A1 molecule, the only significant encephalitogenic site active in the guinea pig. For the mammalian proteins, the essential requirements of Trp-X-X-X-X-Gln-Lys(Arg) were preserved and account, therefore, for the encephalitogenic activity of these proteins. The rat and human proteins contain arginine rather than lysine at position 122 of the A1 sequence, an acceptable substitution. Thus the amino acid sequences of mammalian A1 proteins in the tryptophan region appear virtually identical. The sequence was inferred from analysis of the tryptophan-containing peptides obtained by peptide mapping of both the tryptic and chymotryptic digests. |
