Repertoire of peripheral T cells in patients with oral squamous cell carcinoma

Background The establishment of adaptive immune responses to neoplasms involves not only the tumour tissue, but also the peripheral blood. We aimed to conduct a preliminary exploration to understand the immune response of T lymphocytes of peripheral blood mononuclear cells (PBMC‐Ts) in oral squamous cell carcinoma (OSCC). Methods A total of 103 blood samples from OSCC patients and 18 blood samples from healthy donors (HD) were analysed by flow cytometry. Results Compared to those in HD, a series of unique features of PBMC‐Ts were observed in OSCC patients including a significant increase in CD4+ T cells, a shift from naïve to memory/effector phenotype, an increased frequency of exhausted phenotypes (programmed death‐1 [PD‐1], T cell Ig and mucin protein‐3 [Tim‐3] and Tregs), an abundance of Th17s and Tc17s and an imbalance in Th17/Tc17 and Th17/Treg ratios. Furthermore, in OSCC patients, we also found that CD4+ T cells were significantly increased in patients with larger tumours than smaller tumours, memory/effector phenotype and exhausted phenotypes were significantly associated with advanced clinical stage and lymph node metastasis, and the Th17/Treg ratio was associated with early clinical stage and no lymph node metastasis. Conclusion PBMC‐Ts may be involved in the development and progression of OSCC, which suggested to be a manifestation of an immune response between host and tumour neoantigens.