In particular, it has been shown that: 1) The C activation contribute to the covid-19 pathogenesis regulating a systemic pro-inflammatory response: in a mouse model, mice deficient in C3 (C3−/−), the central component of the C system, exhibited significantly less respiratory disorders, fewer neutrophils and inflammatory monocytes, lover cytokine levels to C56BL/6J control mice, despite similar viral titers detected in the lungs (2). The gene discussed is C3; the disease is respiratory system disorder.