Role of early cytokines, including alpha and beta interferons (IFN-alpha/beta), in innate and adaptive immune responses to viral infections.

Innate cytokine responses are important mediators of early defense against infections. Certain of their effects can be delivered directly to activate protective mechanisms in infected cells. Others activate innate immune cells, including natural killer (NK) cells and macrophages, to mediate defense. Still others shape adaptive immune responses. The compositions and magnitudes of innate cytokine responses are modulated, by the nature of the infectious agent, to facilitate accessing of the anti-microbial defense functions most beneficial in defense against the particular infection. In the context of viral infections, interferons alpha and beta (IFN-alpha/beta) are induced to high levels, and help to mediate and regulate immune responses most effective against this class of agents. The cytokines induce anti-viral mechanisms in infected cells, negatively regulate interleukin 12 expression, and activate NK cell-mediated lysis. Protective development of adaptive immunity to viral infections includes prominent CD8 T cell expansion and activation, and IFN-alpha/beta can mediate functions with the potential to promote these T cell responses. Together, the characteristics define regulation of unique or unique prominent defense mechanisms in place to fight off viral infections. Copyright 1998 Academic Press.