IL6 and COVID-19: The hypothesis that blocking IL-6 or GM-CSF will be beneficial is based in part on the finding that IL-6 and GM-CSF and/or the cells that express them are increased in the blood of COVID-19 patients22,41 and on the beneficial results froma preliminary single-arm trial of an IL-6 receptor blocker, which reportedly lowered fever and improved oxygenation in COVID-19 patients43.