Innate Immunity: Defeating

The innate immune response consists of a variety of relatively nonspecific and short-lived responses typically triggered soon after the appearance of an antigen (such as a virus or other pathogen). These responses have evolved, in part, to eliminate or to contain infectious agents such as viruses and often also serve to promote adaptive (antigen-specific B-cell and T-cell) immune responses. Innate immune responses can be mediated by proteins, for example, interferons, other cytokines, or complement; and by specific cell types such as macrophages, dendritic cells, and natural killer cells. Having co-evolved with their hosts, it is not surprising that viruses have developed ways to defeat innate immune responses. For virtually any described effector of the innate immune response, an example can be found of a virus-encoded mechanism to counteract this host response. The capacity to defeat these host responses is critical for efficient virus replication and for virus pathogenesis.