IL6 and COVID-19: Strikingly, combined stimulation of anti-spike IgG immune complexes and the toll-like receptor 3 agonist, polyinosinic:polycytidylic acid (poly(I:C)) increased the production of COVID-19-associated pro-inflammatory cytokines IL-1β, IL-6, and TNF compared to IgG or poly(I:C) alone (Fig. 1A).