innate immune system

Innate Response to Viral Infection

A viral infection is detected by changes in MHC levels on infected cells as well as activation of TLR3 by dsRNA.

All cells in general…

  1. Are alerted by TLR3 to the viral infection, causing the production of interferon β from the infected cell.
  2. Interferon β acts in an autocrine and paracrine mode to cause the production of interferon α and invoke an anti-viral state, leading to the degradation of dsRNA and inhibition of protein synthesis.

NK cells…

  1. Are activated by interferon α and interferon β produced by infected cells and activated macrophages.
  2. They are usually inhibited from killing normal cells by negative signals (e.g. MHC), but are now prompted to kill infected and damaged cells by positive activation signals.

Infected cells produce positive receptors for NK killing, leading to…

  1. Binding of the NK cell to the target cell.
  2. NK cell releases perforin by fusing membrane vesicles with the cell membrane.
  3. Perforin generates a pore in the cell membrane of the target cell, allowing granzymes to enter.
  4. Granzymes are a class of proteases that induce apoptosis, causing death of the target cell.