Thymic myoid cells express high levels of muscle genes.

To explore the possible contribution of thymic myoid cells in tolerance induction mechanisms, we quantified by real-time RT-PCR, the expression of 12 muscle genes (the five subunits of acetylcholine receptor, Musk, rapsyn, utrophin, ErbB2, ErbB3, troponin T, and MCK) in a human thymic myoid cell line (MITC), compared to thymic epithelial cells (TEC) and thymocytes. Although expression of all the genes analyzed was detected in TEC and thymocytes, the level of expression in these cells was much lower than in MITC, except for -AChR, utrophin and ErbB3 genes. Since myoid cells express high level of most muscle genes and are consistently found in the thymic medulla, they may contribute to the mechanisms involved in the induction and maintenance of immune tolerance.