[Localization of NMDAR-related epitopes in ovarian teratoma: comparison between patients and controls]

To clarify the role of ovarian teratomas in the pathogenesis of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, we examined histopathologically ovarian teratomas with and without encephalitis as well as normal ovaries. We found strong expression of N-methyl-D-aspartate receptor subtype 2B (NR2B) epitopes in the cytoplasm of oocytes obtained from human and bovine ovaries. A substantial amount of neural tissues expressing NR2B immunoreactivity chiefly in the mature neurons was observed. However, between both groups of ovarian teratomas, no significant difference in either the amount of neural tissues or the degree of inflammatory cell infiltration was observed. Young females comprise around 80% of all anti-NMDAR encephalitis patients, and it has been reported that 39% of them have ovarian teratomas. It is also well known that the vast majority of encephalitis patients have prodromal infection before onset of the disease. If this infection affects either normal ovaries or ovarian teratomas, it may trigger the expression of NMDAR-related epitopes in oocytes. Therefore, ovarian teratomas that consist of large amounts of neural tissue might indicate an increased risk for development of this type of intractable encephalitis.