Experimental allergic neuritis: cells binding horseradish peroxidase conjugates of myelin basic proteins

In rabbits with experimental allergic neuritis induced by inoculation with purified bovine peripheral myelin, the authors demonstrated mononuclear cells specifically binding a conjugate of horseradish peroxidase and bovine P2 protein. The P2 protein is one of the 2 basic proteins of peripheral myelin and is unique to the peripheral nervous system. The specifically reactive cells were present in lymph nodes and in infiltrates in dorsal root ganglia, a target organ in this autoimmune disease. Many of the reactive cells in both sites resembled plasma cells and large lymphocytes. No cells bound a conjugate of peroxidase and the encephalitogenic basic protein from bovine central myelin, which appears to be chemically identical and is immunopathologically cross reactive with P1 protein, the other basic protein of peripheral myelin. These immunopathologic results are consistent with the clinical and histologic findings that peripheral myelin induces only neuritis and not encephalomyelitis despite its content of both P1 and P2 proteins. They suggest that within intact peripheral myelin, the antigenic sites on P1 protein are masked, whereas those on P2 protein are free to act as immunogens. In rabbits immunized with purified P2 protein, lymph nodes also contained cells binding the P2 protein peroxidase conjugate. These animals, however, did not develop definite evidence of experimental allergic neuritis.