The TIGIT^{+}FOXP3^{+}Treg subset (TIGIT^{+}Tregs) exerts robust suppressive activity on cellular immunity and predisposes septic individuals to opportunistic infection. We hypothesized that TIGIT^{+}Tregs could play an important role in intensifying the COVID-19 severity and hampering the defense against nosocomial infections during hospitalization. Herein we aimed to verify the association between the levels of the TIGIT^{+}Tregs with the mechanical ventilation requirement, fatal outcome, and bacteremia during hospitalization. TIGIT^{+}Tregs were immunophenotyped by flow cytometry from the peripheral blood of 72 unvaccinated hospitalized COVID-19 patients at admission from May 29th to August 6th, 2020. The patients were stratified during hospitalization according to their mechanical ventilation requirement and fatal outcome. COVID-19 resulted in a high prevalence of the TIGIT^{+}Tregs at admission, which progressively increased in patients with mechanical ventilation needs and fatal outcomes. The prevalence of TIGIT^{+}Tregs positively correlated with poor pulmonary function and higher plasma levels of LDH, HMGB1, FGL2, and TNF. The non-survivors presented higher plasma levels of IL-33, HMGB1, FGL2, IL-10, IL-6, and 5.54 times more bacteremia than survivors. Conclusions: The expansion of the TIGIT^{+}Tregs in COVID-19 patients was associated with inflammation, lung dysfunction, bacteremia, and fatal outcome.
【저자키워드】 immunology, Inflammation, Adaptive immunity, Infectious diseases, Lymphocytes, T cells,