C5 and COVID-19: Taking this into account, and due to the fact that C5a receptor 1 (C5aR1) levels are also increased in lung neutrophils of severe COVID-19 patients, a study showed anti-C5aR1 therapeutic monoclonal antibodies can fight against C5a action and avoid the infiltration of human myeloid cells in damaged organs, preventing the inflammation developed in severe COVID-19 patients (91).