Infrequent and low AIRE expression in thymoma: difference in AIRE expression among WHO subtypes does not correlate with association of MG.

Thymoma is frequently associated with autoimmune diseases, including myasthenia gravis (MG). The failure of thymoma microenvironment to induce T cell tolerance may be responsible for its association of MG. Autoimmune regulator (AIRE) expression in the medullary thymic epithelial cells has been reported to play a role in presenting autoantigen and induction of tolerance. We studied AIRE mRNA in 45 thymomas and three normal thymi using quantitative reverse transcription polymerase chain reaction (RT-PCR). Only 23/45 (51.1%) of thymomas expressed AIRE mRNA at low levels while all normal thymi expressed AIRE mRNA. There was no correlation between AIRE mRNA and association of MG or presence of anti-acetylcholine receptor antibody. The infrequent and low expression of AIRE mRNA may play a role the induction of autoimmune diseases but other factors also seem to be involved.