Reduction of natural regulatory T cells in thymomas accompanying myasthenia gravis and its possible association with Foxp3 and thymic stromal lymphopoietin

ObjectiveTo investigate the expression of both thymic regulatory T cells (CD4+ CD25+ Foxp3+ cells, Treg) and thymic stromal lymphopoietin (TSLP) in thymomas accompanying myasthenia gravis.MethodsWe used immunohistochemistry and real-time reverse trancription polymerase chain reaction (real-time RT-PCR) techniques to determine Foxp3+ Treg counts and the expression levels of Foxp3 mRNA and TSLP mRNA in thymomas of 23 MG patients and thymuses of 4 healthy controls.ResultsThe CD4+ Foxp3+ nTreg (natural regulatory T cells) counts in thymomas were significantly lower than those in normal thymuses (P<0.01), and the expression levels of Foxp3 mRNA and TSLP mRNA were also lower in thymomas(P<0.01). Among the thymoma types, type B1 thymoma had the highest Foxp3+ nTreg count and standard values of Foxp3 mRNA and TSLP mRNA. There was a strong positive correlation between the mRNA transcriptional levels of Foxp3 and TSLP.ConclusionThe insufficient expression of Foxp3 in thymoma, which may be caused by decreased transcription of TSLP, may result in the reduction of Tregs and cause autoimmune disorders.