Highlights The cytotoxic protein PRF1 is essentially involved in anti-tumour immunity. PRF1 is overexpressed in advanced HPV+ HNSCC and correlates with better OS. PRF1 expression correlates with tumour infiltrating CD8+ t cells and dendritic cells in HPV+ HNSCC. PRF1 expression correlates with gene markers of t cell exhaustion in HNSCC.

Objective We aim to review the roles of plasmacytoid dendritic cells (pDCs) in head and neck squamous cell carcinoma (HNSCC) and explore the effects of hypoxia on the tolerogenic transformation of pDCs. Background pDCs, best known as professional type I interferon‐secreting cells, play key roles in immune surveillance and antitumor immunity. Recently, pDCs have been shown to be tolerogenic and correlate with poor prognosis in a variety of cancers, including HNSCC. However, it remains unclear what drives the tolerogenic transformation of pDCs in the HNSCC microenvironment. Hypoxia, a prominent hallmark of the tumor microenvironment (TME) of HNSCC, can interfere with multiple immune cells and establish an immunosuppressive TME. Methods In this review, we summarize the antitumor and protumor functions of pDCs, explore the effects of hypoxia on the migration and maturation of pDCs, and discuss related mechanisms in HNSCC. Conclusions pDCs mainly display protumor functions in HNSCC. The hypoxic TME in HNSCC can enhance the migration of pDCs and inhibit the differentiation and maturation of pDCs, promoting the tolerogenic phenotype of pDCs.

A great number of patients with Coronavirus Disease 2019 (COVID-19) experience olfactory dysfunction, typically of a short duration and with a high incidence rate, during the early stages of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This kind of olfactory dysfunction appears more likely in young people and women. This study presents a review of the clinical features and pathogenic mechanism of the olfactory dysfunction related to SARS-CoV-2 infection, aiming to provide a clinical reference for the diagnosis, differential diagnosis, treatment, and prevention of olfactory dysfunction in COVID-19 patients.