The thymoproteasome subunit b5t is specifically expressed in cortical thymic epithelial cells (TECs) and generates unique peptides to support positive selection. In this study, using a mouse model ubiquitously expressing b5t, we showed that aberrant expression of self-peptides generated by b5t affects CD8 + T cell homeostasis, including thymic selection and maintenance of the peripheral naive pool of CD8 + T cells. In mice in which b5t was expressed both in cortical and medullary TECs, the abundance of CD8 + lineage thymocytes was reduced, and extra-thymic expression of b5t caused accumulation of CD8 + T cells with the memory or exhausted phenotype and induced autoreactive T cell responses. We found that thymoproteasomes are essential for positive selection but that the subsequent change in peptide repertoire in the medulla is also crucial for thymic selection and that b5t-derived peptide must be confined to the thymus to avoid autoimmunity in peripheral tissues.

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We report an extremely rare case of branchial cleft-like cysts in Hashimoto's thyroiditis. The patient was a 77-year-old man with a growing mass in the anterior neck. Ultrasonography and computed tomography revealed a cystic lesion with septum in the left thyroid and multiple small cystic lesions in the right thyroid. Lymph node swelling of the cervical region, supraclavicular fossa and submandibular region was also observed. Left thyroidectomy and lymph node dissection were performed. Histologically, cysts were lined by stratified squamous epithelium and dense lymphoid tissue having conspicuous follicle formation surrounded the epithelial lining. Solid cell nest (SCN)-like aggregations were seen in the thyroid parenchyma adjacent to the cyst walls and a small number of thyroid follicles were observed in the fibrous wall. Immunohistochemically, it is suggested that both the cyst lining and SCN-like aggregations are originally from thyroid follicles. Although, the exact histogenesis of branchial cleft-like cysts remains unclear, there are probably two different processes for its development, one is of branchial cleft origin and the other is mere squamous metaplasia, while in our case the latter is suggested. Herein, we report our new case and update information about branchial cleft-like cysts that appears in the literature.

The uncommon mutations in the EGFR (the epithelial growth factor receptor) gene include a heterogeneous group of genomic alterations within exons 18-21. The clinical response of patients with such mutations to EGFR tyrosine kinase inhibitor (EGFR-TKI) treatment, however, remains unclear. We herein report a case of advanced lung adenocarcinoma harboring complex exon 18 G719X (Gly719Xaa) and exon 20 S768I (Ser768Ile) mutations. The patient started to receive afatinib and has exhibited good response without progression for 12 months. Second-generation EGFR-TKIs might be an optimal treatment option for non-small cell lung cancers harboring these types of rare EGFR mutation.