Comparative histology of experimental allergic neuritis induced with minimum length neuritogenic peptides by adoptive transfer with sensitized cells or direct sensitization.

Using synthetic peptides representing specific regions of the bovine myelin protein P2, the minimum peptide length requirement for the T-cell epitope necessary for successful production of experimental allergic neuritis (EAN) has been shown to involve residues 61-70 of the P2 protein. In this study, morphometric analysis was used to compare the histologic changes in sciatic nerves of Lewis rats after disease was induced by P2 specific neuritogenic T-cell lines (P(2)3) or, alternatively, by direct inoculation of synthetic peptides representing residues 60-70 or 61-70 of the P2 protein sequence. Inoculation with cell line P(2)3 stimulated with residue 61-70 failed to elicit demyelination in sciatic nerves. However, cells stimulated with residue 60-70 produced inflammation, endoneurial edema, mild demyelination and axonal degeneration within seven days. In contrast, disease induced with either peptide by direct sensitization was more severe. Morphometric analysis revealed that inflammation was most severe in animals sensitized to the decapeptide. In the sciatic nerve, axonal degeneration was proportional in frequency to the extent of inflammation. Inflammation was especially intense in spinal roots with extensive destruction of axons including unmyelinated fibers. Spinal root changes were associated with Wallerian degeneration in the posterior white matter tracts of the spinal cord and were apparently secondary to endoneurial inflammation. Disruption of the blood-nerve-barrier (BNB), evident as physical separation of endothelial cells in association with severe perivascular inflammation, was observed.