Interferons

What do interferons (IFNs) do?

• transiently inhibits the multiplication of viruses in most cells by interfering with viral replication

  • triggers the production of virus-blocking enzymes by potential host cells. The enzymes remain inactive unless cells are attacked by viruses

• bind to and forewarn neighboring cells to viral attack.

• slows cell division (has anticancer effects)

Specific or nonspecific?

nonspecific

Where do gamma (immune) IFNs come from?

lymphocytes

Where do Alpha IFNs come from?

• come from all cells in the body; other leukocytes

• from vid: secreted by virally infected leukocytes (monocytes [macrophages] and some lymphocytes)

Where do Beta IFNs come from?

only come fibroblasts

What are IFNs?

type of cytokines, so they’re cell-signaling molecules within our immune system

What are the Type I IFNs? What do they do? How similar are they?

• IFN-ɑ and IFN-β

• interfere with viral replication in uninfected cells + alert immune cells such as NK cells that an infection has occurred

• Identical in structure and function

How does a virus infect a human cell?

Viruses are composed of nucleic acids surrounded by a protein envelope. When they infect a cell, they only secrete their nucleic acid inside a target cell before using the machinery of the cell to produce more viruses

Role of Type I IFNs in Antiviral Defense

• When a virus secretes its nucleic acids into a human cell, the cell produce Type I IFNs

  • All human cells express IFN receptors on their plasma membrane, so once released, the Type I IFNs binds to the receptors on nearby cells

  • Binding generates an internal signal that results in the formation of anti-viral proteins in the uninfected cells that remain unactivated until the virus attacks.

    • Activated viral proteins degrade the viral nucleic acid and inhibit viral protein synthesis

  • Infected cells are not protected by IFNs but are destroyed by NKCs and apoptosis

What IFNs are part of Type II IFNs

IFN-γ (also known as macrophage activation factor)

How does IFN-γ work?

• Produced by activated T-lymphocytes and NK cells

• Stimulate the activity of macrophages

• Part of adaptive immunity