COVID-19 is a disease with an initial viral phase followed, usually at the 7th day, of an inflammatory state (cytokine storm) leading to respiratory distress, ICU admission and risk of death. Thus, several biological agents, antagonists of the different cytokines (IL-6, IL-1) have been used for patients with severe disease. However, there are no data about the cytokine changes, at admission and after therapy, and its predictive value, a fundamental knowledge to establish the best therapeutic strategy.

The first line of immune defense is the interaction of the virus with innate immunity cell members. The toll like receptors (TLRs) family is a group of pattern recognition receptors that include many different molecules (21-23). These bindings can activate dendritic cells, monocytes, macrophages. There is an important RNA and DNA connection, activation of TLRs, the production of type I interferons, and the development of some autoimmune diseases. TLR7 and TLR8 specifically recognize simple-chain RNA of viruses and are expressed in endosomal membranes. TLR8 is expressed in regulatory cells (Treg) and its activation results in inhibition of its regulatory functions. Natural killer cells (NK) respond to alterations of class I HLA molecules present in infected cells (24-26). An increase in class I HLA expression could lead to an increase in NK activation by increasing its ability to produce IFN-gamma. Therefore, the reasons for KIR binding are often variable between individuals and between populations.