Why is the immune system able to fight off some viruses but not others, leading to chronic, life-threatening infections like HIV and hepatitis C?
A new UCLA AIDS Institute study suggests the answer lies in a protein called interleukin-21 (IL-21), a powerful molecule released by immune cells during chronic infection. Published May 7 in the online edition of Science, the finding could explain how the immune system limits viral replication, restricting a virus's spread through the body.
The researchers looked at two types of T-cells — CD4 T-cells and CD8 T-cells — which are immune cells that play an important role in the body's response to infection. The CD4 T-cells help the immune system by producing IL-21 during chronic infection, bolstering the CD8 T-cells' ability to fight off the virus.
A new UCLA AIDS Institute study suggests the answer lies in a protein called interleukin-21 (IL-21), a powerful molecule released by immune cells during chronic infection. Published May 7 in the online edition of Science, the finding could explain how the immune system limits viral replication, restricting a virus's spread through the body.
The researchers looked at two types of T-cells — CD4 T-cells and CD8 T-cells — which are immune cells that play an important role in the body's response to infection. The CD4 T-cells help the immune system by producing IL-21 during chronic infection, bolstering the CD8 T-cells' ability to fight off the virus.


