Changes

This becomes active during the early stages of infection. Defences include:

This becomes active during the early stages of infection. Defences include:

*Interferon (IFN)- typically stimulates the inhibition of viral replication. There are three known types:

*Interferon (IFN)- typically stimulates the inhibition of viral replication. There are three known types:

**Infection of a cell by a virus stimulates production of IFN-alpha and IFN-beta, which activate genes in neighbouring cells. One of these genes, for example, codes for a protein kinase that blocks translation of proteins. Another activates an endonuclease that degrades viral RNA.  

**Infection of a cell by a virus stimulates production of IFN-α and IFN-β, which activate genes in neighbouring cells. One of these genes, for example, codes for a protein kinase that blocks translation of proteins. Another activates an endonuclease that degrades viral RNA.  

**IFN-γ increases the expression of MHC I and II, enhancing the function of the adaptive immune response. It also activates macrophages and NK cells.

**IFN-γ increases the expression of MHC I and II, enhancing the function of the adaptive immune response. It also activates macrophages and NK cells.

*Natural killer (NK) cells- one of the main mediators of antibody-dependent cell-mediated cytotoxicity

*Natural killer (NK) cells- one of the main mediators of antibody-dependent cell-mediated cytotoxicity