[IL-21 Is Required to Control Chronic Viral Infection.]
>>Science. 2009 May 7. [Epub ahead of print]
IL-21 Is Required to Control Chronic Viral Infection.
Elsaesser H, Sauer K, Brooks DG.
Department of Microbiology, Immunology and Molecular Genetics and the UCLA AIDS Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
CD4(+) and CD8(+) T cell functions are rapidly aborted during chronic infection, preventing viral clearance. CD4(+) T cell help is required throughout chronic infection to sustain CD8 T cell responses; however, the necessary factor(s) provided by CD4(+) T cells are currently unknown. Using a mouse model of chronic viral infection, we demonstrate that interleukin-21 (IL-21) is an essential component of CD4(+) T cell help. In the absence of IL-21 signaling, despite elevated CD4(+) T cell responses, CD8(+) T cell responses are severely impaired. CD8(+) T cells directly require IL-21 to avoid deletion, maintain immunity, and resolve persistent infection. Thus, IL-21 specifically sustains CD8(+) T cell effector activity and provides a mechanism of CD4(+) T cell help during chronic virus infection.<<
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