Antibodies to glycolipids have been implicated in the pathogenesis of several immune-mediated PNS diseases, including paraproteinemic neuropathies, chronic inflammatory demyelinating polyneuropathy (CIDP), and some cases of Guillain-Barre syndrome. This project examines the hypothesis that glycolipids may provide cell-specific targets for antibody-mediated modulation of Schwann cell function. While Schwann cell destruction would be expected to occur in the presence of antibody plus complement, antibody alone may lead to sublethal damage and functional changes in Schwann cells and their interactions with axons or immune cells. Enriched Schwann cell cultures will be prepared from newborn rat sciatic nerves, then differentiated in the presence of 8- bromo cyclic AMP. Cells will be examined for their responsiveness to antibodies to the HNK-1 epitope (glucuronyl sulfate), galactocerebroside and sulfatide; and to the beta subunit of cholera toxin, which binds with high affinity to GM1 ganglioside. Each agent will be examined for its binding to the surface of the Schwann cells, and effects on internalization or shedding of the target glycolipid. Levels of intracellular calcium will be monitored as an indicator of responsiveness of the cells to binding of the ligands to the glycolipids. If Ca++ responses are noted, the roles of pore formation, voltage-gated Ca++ channels or receptor-activated ion channels will be investigated. Regulation of expression of NGF receptor and the myelin proteins PO, MAG and myelin basic protein will be examined by immunocytochemistry, Western blotting and Northern blotting. These experiments will elucidate (a) the responses of Schwann cells to antibodies directed at surface glycolipids, and (b) the roles of glycolipids in Schwann cell function.
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