A study published in Respiratory Research found an association between patients with chronic obstructive pulmonary disease (COPD) and mucosal-associated invariant T (MAIT) cell count in relation to risk of hospitalization. This association was independent of forced expiratory volume in 1 second (FEV1) and categorization according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines.
The study included patients with COPD from the Tools for Identify Exacerbations study in Uppsala. Patients were excluded if they had an established diagnosis of asthma, the asthma-COPD overlap syndrome, speech difficulties, dementia, psychotic disorders, and severe comorbidities associated with expected survival of less than 12 months. Patients with long-term oxygen treatment were also excluded.
Patients were classified according to the GOLD 2017 guidelines based on the COPD Assessment Test, which is a questionnaire meant to assess the impact of COPD on a patient over time. This assessment was conducted during the 3-year follow up.
Patients were recruited and blood was sampled while they were in the stable disease phase. All patients had 3 years of follow-up to record all-case hospitalizations. Patients who required hospitalization in the 3-year follow-up were classified as hospitalized patients and compared with patients who were never hospitalized. Hospitalized patients had lower MAIT cell count at study inclusion but did not differ in CD8 or CD4 T cell counts. Patients who were hospitalized also had lower MAIT cell percentage.
Patients who were hospitalized had MAIT cells that demonstrated a more activated phenotype with higher CD38 expression and MAIT cells and conventional CD8 T cells did not differ between hospitalized and never hospitalized patients.
A multi-variable logistic regression analysis found that MAIT cell count, CD38 expression on MAIT cells, and LAG-3 expression in both MAIT and CD8 T cells were all associated with risk of hospitalization. The FEV1 measure did not correlate with MAIT cell count, MAIT cell frequency, or CD38 or LAG-3 expression of MAIT cells. According to the findings, MAIT cells do not mirror the severity of airflow obstruction and MAIT cells may reflect a FEV1-independent immunological dimension of COPD.
In a logistic regression analysis, hospitalizations were more likely in patients with higher CD38 and LAG-3 expression in MAIT cells that was independent of treatment with inhaled corticosteroids. This test was done due to previous studies finding that patients with COPD treated with inhaled corticosteroids had lower MAIT cell frequency compared with steroid-naïve patients.
There were some limits to this study. The focus of this study was on all-cause hospitalizations rather than COPD exacerbations, which may have limited the study. MAIT cell data was only recorded at a single time-point at baseline when patients were in their stable phase which prevented detecting changes over time. There is also the possibility of selection bias due to the nature of the study.
The researchers concluded that MAIT cell count and expression of the activation markers of CD38 and LAG-3 on MAIT cells in peripheral blood of patients with COPD were associated with risk of hospitalization.
“Our findings support the hypothesis that MAIT cells might reflect a novel FEV1-independent immunopathological dimension in the complexity of COPD,” the authors wrote.
Pincikova T, Parrot T, Hjelte L, et al. MAIT cell counts are associated with the risk of hospitalization in COPD. Respir Res. 2022;23:127. doi:10.1186/s12931-022-02045-2