Experimental allergic encephalomyelitis: immunological properties of encephalitogenic polypeptides and proteins.

Two fractions, a protein and a polypeptide, from extracts of acetone dried powders of central nervous tissue produced experimental allergic encephalomyelitis (EAE) when injected with Freund's complete adjuvant, in doses as minute as 50 ng for the bovine encephalitogenic polypeptide (BEP). All bovine and guinea-pig encephalitogens produced EAE in guinea-pigs but only guinea-pig and not bovine encephalitogens produced EAE in the Wistar rat. The bovine and guinea-pig protein encephalitogens, in the guinea-pig particularly, induced antibody and delayed hypersensitivity against these proteins and EAE. The polypeptide encephalitogen, BEP, induced no humoral antibody reacting with BEP itself, but did induce delayed hypersensitivity to BEP and EAE; however, BEP induced antibody which cross-reacted with the protein encephalitogens from both species. Precipitin reactions with these basic proteins in immunodiffusion were optimal at a slightly acid rather than neutral pH. Observations on cross-reactions among the neural fractions by immunodiffusion and delayed hypersensitivity suggested that a similar encephalitogenic determinant could be present in the various encephalitogens from the two species. Further work with enzymatic digests of our encephalitogenic polypeptides may bring us nearer our goal which is the identification of the molecular grouping in myelin essential for the induction of EAE.