Functional Profile of γδ T Cells in Severe and Moderate COVID-19: A Brazilian Cross-Sectional Study

This study aimed to identify the distinct intrinsic response potential of γδ T cells from COVID-19 patients with different illness severities, to better understand the implication of these cells in COVID-19 disease. Forty-four COVID patients were enrolled at hospitalization and classified as: moderate without oxygen support (MWO₂; N = 15), moderate with oxygen support (MO₂; N = 15), or severe disease requiring mechanical ventilation (SD; N = 14). γδ T cells were characterized ex vivo, isolated from peripheral blood cells, stimulated in vitro with OKT3 and K562 cells, and evaluated for functional markers by flow cytometry. Ex vivo analysis identified 16.21% of total γδ T cells as Vδ1^-Vδ2^-. SD patients presented a lower frequency of TRAIL⁺ and of IL-17-producing Vδ2 cells, as well as lower value of fluorescence intensity values for TNF-α in Vδ2 cells, than MWO₂ patients (p < 0.05). In addition, paired analyses showed a lower frequency of IL-17-producing than CD161⁺ Vδ2 cells in SD patients (p < 0.05). These observations suggest a more restricted response potential of the Vδ2 subset in severe disease, show the impact of general immune dysregulation on these cells, or even suggest some role for IL-17-producing Vδ2 cells in preventing critical symptoms.