Expression of antigen processing and presenting molecules by Schwann cells in inflammatory neuropathies

Schwann cells are the myelinating glia cells of the peripheral nervous system (PNS) and can become targets of an autoimmune response in inflammatory neuropathies like the Guillain-Barré syndrome (GBS). Professional antigen presenting cells (APCs) are known to promote autoimmune responses in target tissues by presenting self-antigens. Other cell types could participate in local autoimmune responses by acting as nonprofessional APCs. Using a combined approach of immunocytochemistry, immunohistochemistry, and flow cytometry analysis we demonstrate that human Schwann cells express the antigen processing and presenting machinery (APM) in vitro and in vivo. Moreover, cultured human Schwann cells increase the expression of proteasome subunit delta (Y), antigen peptide transporter TAP2, and HLA Class I and HLA Class II complexes in an inflammatory environment. In correlation with this observation, Schwann cells in sural nerve biopsies from GBS patients show increased expression of antigen processing and presenting molecules. Furthermore, cultured human Schwann cells can proteolytically digest fluorescently-labeled nonmammalian antigen ovalbumin. Taken together, our data suggest antigen processing and presentation as a possible function of Schwann cells that may contribute to (auto)immune responses within peripheral nerves.