Immunity phenomena following olfactory ensheathing cell transplantation into experimental allergic encephalomyelitis rat brain

Olfactory ensheathing cells (OECs) can promote axonal regeneration and remyelination for the treatment of spinal cord injury. OECs can also treat experimental allergic encephalomyelitis (EAE), but it remains unclear whether OECs might be rejected by the immune system in the brain, including the destruction of the blood-brain barrier under inflammation, the release of inflammatory factors, the activation of local antigen-presenting cells (e.g., microglia cells) and antigen drainage. We found that OECs expressed major histocompatibility complex (MHC)-I molecules on the cell surface, barely expressed MHC-II, but MHC-II could be induced by interferon-gamma, suggesting that OECs have certain immunogenicity. When OECs were transplanted into normal animal brains, no OECs were phagocytosed by dendritic cells in the cervical lymph node, and OECs did not induce lymphocyte proliferation, which indicates that OECs share some immune privilege under normal conditions. However, OECs in the rat EAE brain were phagocytosed by dendritic cells in the cervical lymph node and enhanced lymphocyte proliferation. These findings suggest that OECs are rejected because of increased immunogenicity in EAE brain, and that brain inflammation, in particular activated dendritic cells, may be a prerequisite for rejecting OECs.