In contrast, early induction of IL-10 appears to play detrimental roles in host response against Ehrlichia. More importantly, the ratio between pro- and anti-inflammatory cytokines and differential kinetics of their production during course of lethal and nonlethal ehrlichial infection are important factors that seems to govern the outcome of infection, degree of pathology, and host immune responses during mild and severe ehrlichiosis. The gene discussed is IL10; the disease is infection.