The study associated the expression of CX3CR1, a member of the chemokine receptor superfamily, mostly expressed on cytotoxic effector lymphocytes (e.g. NK cells, CD8+ T and macrophages), with the pathological mechanism of severe COVID-19, and suggested that the elevated methylation lowered the expression of CX3CR1 in immune cells and contributed to the aberrant antiviral response in COVID-19 [92]. This evidence concerns the gene CX3CR1 and COVID-19.