C3 and erythema multiforme: We consider that a complement C3 inhibitor could be used as a treatment for EM, exerting two potentially beneficial effects: on the one hand, one would attain an interruption from the beginning of the cascade of inflammatory signals that plays an important role in the pathogenesis of EM; on the other hand, a lower production of iC3b would result in a lower inhibition of the cytotoxic activity of the NK cells.