DETECTION AND QUANTIFICATION OF ANTIBODIES TO THE EXTRACELLULAR DOMAIN OF P0 DURING EXPERIMENTAL ALLERGIC NEURITIS

Quantification of the peripheral nerve myelin glycoprotein P0 and anti bodies to P0 is difficult due to insolubility of P0 in physiological s olutions. We have overcome this problem by using the water-soluble rec ombinant form of the extracellular domain of P0 (P0-ED) and describe n ewly developed assays which allow detection and quantitation of P0 and antibodies to P0, in serum and cerebrospinal fluid (CSF). These sensi tive and specific assays based on the ELISA technique were used to stu dy humoral immune responses to P0 during experimental autoimmune (''al lergic'') neuritis (EAN). In order to establish these tests, monoclona l antibodies to different epitopes of rodent and human P0-ED were prod uced. A two-antibody sandwich-ELISA allowing quantitation of P0 (lower detection limit of 0.5 ng/ml or 30 fmol/ml) and an antibody-capture E LISA (lower detection limit 1 ng specific antibody/ml) to detect antib odies to P0 in serum and CSF were developed. EAN was induced in rats b y active immunization with bovine myelin or the neuritogenic protein P 2 or by adoptive transfer using P2 specific CD4 positive T cells. Seru m and CSF were assayed for the presence of P0-ED and antibodies to P0- ED or P2. Antibodies to P0-ED were detected during active myelin-induc ed EAN, but not during P2-induced or adoptive transfer EAN. The anti-P 0-ED antibodies in the CSF showed a correlation with disease activity. In contrast, in the same model antibodies to P2 persisted long after the disease ceased. No soluble P0-like fragments could be found in ser um or CSF during any of the three types of EAN. We conclude that P0 ma y be a B-cell epitope in EAN. These findings warrant a screen for anti bodies to P0-ED in human immune neuropathies.