Interferon-alpha primes macrophages for lipopolysaccharide-induced apoptosis.

Apoptosis plays an important role in generating and maintaining an effective immune system. Many pathogens can perturb the homeostasis of the immune system by either inducing or suppressing cell death of immune cells. Using bovine macrophages as a model, we found that interferon-alpha, one of the host's responses to viral infection, can prime macrophages for activation-induced apoptosis. Exposure of bovine bone-marrow-derived macrophages to interferon-alpha and subsequent activation with lipopolysaccharide led to a strong downregulation of the macrophages' nitric oxide production when compared to lipopolysaccharide stimulation alone. We could show that this was due to induction of apoptosis after activation of the cells. Herpesvirus-induced type I interferon also primed bovine macrophages for lipopolysaccharide-induced apoptosis. Our studies describe how in a novel pathway an antiviral immune response could contribute to pathological sequelae of viral diseases.