The following is a summary of “Type 17 mucosal-associated invariant T cells contribute to neutrophilic inflammation in patients with nasal polyps,” published in the November 2023 issue of Allergy & Immunology by Ye, et al.
The immune regulation mechanisms in chronic rhinosinusitis with nasal polyps (CRSwNP) characterized by a neutrophilic endotype remained unclear. Mucosal-associated invariant T (MAIT) cells, as tissue-resident innate T lymphocytes, play a crucial role in rapid pathogen response and the promotion of chronic mucosal inflammation. For a study, researchers sought to investigate the roles of MAIT cells in neutrophilic CRSwNP.
Nasal tissues were obtained from 113 patients with CRSwNP and 29 control subjects. The analysis involved flow cytometry to examine peripheral and tissue MAIT cells and their subsets. Polyp-derived MAIT cells were further analyzed through RNA sequencing to understand their effects on neutrophils.
CRSwNP endotypes were classified as paucigranulocytic, eosinophilic, neutrophilic, and mixed granulocytic. MAIT cell frequencies were significantly higher in neutrophilic (3.62%) and mixed granulocytic (3.60%) polyps compared to control mucosa (1.78%). The percentages of MAIT cells positively correlated with local neutrophil counts. MAIT cells were more enriched in tissues than in matched peripheral blood mononuclear cells. The frequencies of the MAIT1 subset or IFN-γ+ MAIT cells were comparable among control tissues and CRSwNP subtypes. However, the proportions of the MAIT17 subset or IL-17A+ MAIT cells were significantly increased in neutrophilic or mixed granulocytic polyps compared with controls. RNA sequencing revealed type 17 and pro-neutrophil profiles in neutrophilic polyp–derived MAIT cells. In patients with neutrophilic CRSwNP, the proportions of MAIT and MAIT17 cells were positively correlated with local proinflammatory cytokines and symptom severity. In vitro experiments demonstrated that neutrophilic polyp–derived MAIT cells promoted neutrophil migration, survival, and activation.
MAIT cells from neutrophilic CRSwNP exhibited type 17 functional properties and played a role in promoting neutrophil infiltration in the nasal mucosa.