Detection of Microbiota from Human Thymus of Myasthenia Gravis

Abstract

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies directed against different components of the neuromuscular junction (NMJ), and pathogenic mechanism associated thymic pathologies. Microbiota invading thymus is hypothesized to trigger human autoimmune response by providing antigens to produce NMJ antibodies and clinical manifestations of myasthenia gravis. There are many reports of microbial nucleic acid isolation and protein expression and even a few studies of viable microbes isolated from the human thymus. However, high-resolution investigation of microbial infectious agents from the human thymus that may contribute to myasthenia gravis is very limited. To investigate potential microbial infection within human thymus tissue samples, we performed quantitative real-time PCR of the bacterial 16S ribosomal RNA (rRNA) and fungal 18S rRNA gene analysis on (1) a total of 23 abnormal thymus including 13 thymomas and 4 thymus hyperplasias obtained from MG patients and 6 thymoma-nonMG patients who underwent thymectomy. (2) Another 14 normal thymus were selected as control from patients who underwent congenital heart disease surgery. Results show that a wide range of bacteria agents are exhibited in the thymus, rather than fungus. And an intriguing new observation that shows the microbiota displayed differences among MG patients, thymoma-nonMG patients, and normal thymus as judged from the taxonomic profiles in these three groups. Compared with the normal thymus group, the Klebsiella and Escherichia coli show higher abundance in MG patient group. The thymus harbors bacteria agents and Klebsiella and Escherichia coli may be potential pathogens associated with MG. Further investigations are needed to elucidate the possible associations of Klebsiella and E. coli and MG.