The significance of immune reactions against peripheral nervous system antigens in the human inflammatory polyneuropathies is still uncertain. Using a very sensitive assay, we found greatly increased levels of anti-P2 antibodies in sera of animals with experimental allergic neuritis (EAN) but no increases in humans with acute Guillain-Barre syndrome (GBS), chronic relapsing polyneuritis (CRIP), axonal neuropathy, or normals. P2 protein and CNS basic protein did not induce any increased proliferation in lymphocytes of GBS or CRIP patients. We conclude that P2 and BP appear unlikely to be targets for humoral or cellular immune reactivity in GBS or CRIP.