Interleukin-28 and 29: new cytokines with anti-viral activities.

The signal required for the activation of helper and delayed type hypersensitivity-reactive cells involves the synthesis and release of several soluble factors termed interleukins (1). These factors are also potent inflammatory proteins (2-36) along with other compounds such as arachidonic acid products (36-45). The recruitment of T cells is a critica1 step in resolving viral infections; cytokines and chemokines play an important role in this process.