Mast cells and virus

Mast cells (MCs) are hematopoietic cells that reside ubiquitously in all vascularized tissues. They are potential sources of a wide variety of biologically active secreted compounds, including diverse cytokines, chemokines and growth factors. In addition, they participate in innate and adaptive immune responses. MCs are the most important cells in immediate reactions and chronic IgE-associated allergic disorders and enhance the host resistance to certain biological agents, including viruses. Therefore, MCs influence many biological responses to viruses and other microbiological agents. Viruses activate MCs through TLR4 leading to the generation of several pro-inflammatory cytokines, including those of the IL-1 family. Here, we report how viruses can activate MCs producing severe inflammation and how these interesting cells can activate the immune system by carrying out a protective action for our organism.

Antibodies for COVID-19 - which, when and how long?

Infection with SARS-CoV2 leads to COVID-19, the severity of which derives from the host's immune response, especially the release of a storm of pro-inflammatory cytokines. This coronavirus infects by first binding to the ectoenzyme Angiotensin Converting Enzyme 2 (ACE2), a serine protease acting as the receptor, while another serine protease is necessary for priming the viral spike "S" protein required for entering the cells. Repurposing existing drugs for potential anti-coronavirus activity have failed. As a result, there were intense efforts to rapidly produce ways of providing prophylactic active immunization (vaccines) or abortive passive (convalescent plasma or monoclonal antibodies) neutralizing antibodies. The availability of vaccines for COVID-19 have been largely successful, but many questions still remain unanswered. In spite of the original enthusiasm, clinical studies using convalescent serum or monoclonal antibodies have shown limited benefit. Moreover, the emergence of Long-COVID syndrome in most infected patients necessitates the development of treatment approaches that may prevent viral entry by blocking both serine proteases involved, as with a liposomal blend of the natural flavonoids luteolin and quercetin.