A positively charged protein found in peripheral nervous system MYELIN. Sensitive immunological techniques have demonstrated that P2 is expressed in small amounts of central nervous system myelin sheaths of some species. It is an antigen for experimental allergic neuritis (neuritis, EXPERIMENTAL ALLERGIC), the peripheral nervous system counterpart of experimental allergic encephalomyelitis. (From Siegel et al., Basic neurochemistry, 5th ed, p133)