Final answer:
IFN-a and IFN-B bind to circulating NK cell's IFN receptors to inhibit viral replication.
Step-by-step explanation:
IFN-a and IFN-B bind to circulating NK cell's IFN receptors to inhibit viral replication. Interferons are early-acting cytokines released by infected cells as a warning to nearby uninfected cells. They work by signaling neighboring uninfected cells to destroy RNA and reduce protein synthesis and signaling neighboring infected cells to undergo apoptosis (programmed cell death) and activating immune cells.