Antigen presentation in the peripheral nervous system: Schwann cells present endogenous myelin autoantigens to lymphocytes.

Schwann cells (SC) isolated from neonatal rat sciatic nerves are shown to immunogenically present foreign and exogenous autoantigen to antigen-specific syngeneic T line cells in vitro. The antigen-presenting SC express Ia antigens on their membranes upon treatment with interferon gamma and contact with syngeneic T line cells. Monoclonal antibodies against Ia block specific antigen presentation, but not polyclonal mitogenic T cell activation. The antigen-presenting SC bind antibodies specific for astrocytic glial fibrillary acidic protein and may thus be related to the nonmyelinating glia cells of the peripheral nerve. Furthermore, SC isolated from 6-day-old rats activate rat myelin basic protein (MBP)-specific syngeneic T line cells in the absence of exogenous MBP. In contrast, they activate purified protein derivative of tuberculin (PPD)-specific T cells only in the presence of PPD. Since the MBP-specific T line cells are not activated by syngeneic professional antigen-presenting cells in the absence of MBP, endogenous MBP produced in the 6-day-old sciatic nerves appears to be presented by autochthonous SC to the autoreactive T cells.