Press releases
Please quote Nature Immunology as the source of these items.
The November 2007 issue of Nature Immunology is available online.
November 2007
Fountain of youth
Researchers have identified the cells that provide an essential survival factor to newly created immune cells according to a report published online in Nature Immunology this week.
White blood cells known as T lymphocytes are born in the thymus and these cells are required to fight off viral and other infections. Upon leaving the thymus these cells prowl throughout the body seeking out potential foreign agents; however, the survival of these cells depends on periodic visits to lymph nodes, where they can 'recharge' by receiving a chemical signal called interleukin 7 (IL-7).
It was known for many years that IL-7 provides ‘survival’ signals to these naive T cells, but what actually produced IL-7 proved elusive. Sanjiv Luther and colleagues identify specialized 'fibroblastic reticular cells' found in lymph nodes and spleen as the source of IL-7. These cells make chemical signals that direct T cells to them and supply the essential IL-7 that prevents T cells from dying, thereby allowing them to continue to recirculate throughout the body searching for enemies.
Fibroblastic reticular cells in lymph nodes regulate the homeostasis of naive T cells
Alexander Link, Tobias K Vogt, Stéphanie Favre, Mirjam R Britschgi, Hans Acha-Orbea, Boris Hinz, Jason G Cyster & Sanjiv A Luther
Published online: 23 September 2007 | doi 10.1038/ni1503
HIV stuns immune cells
A known suppression factor in the immune system increases in HIV-infected individuals on critical immune cells, reports a study in the November issue of Nature Immunology. Key targets of HIV infection, CD4+ T cells show elevated levels of the suppression factor and are associated with rapid HIV disease progression.
Bruce Walker and colleagues evaluated HIV-positive people who progressed relatively fast to disease and found significant increases in CTLA-4 expression on CD4+ T lymphocytes compared to those who did not— so-called 'long-term non-progressors'. The team also compared CTLA-4 expression on CD4+ T cells in people before and after receiving highly active anti-retroviral therapy and found higher T cell-associated CTLA-4 in those who were off therapy. Importantly, the team found that blocking the activity of CTLA-4 improved immune function.
These results suggest that decreasing CTLA-4 expression on CD4+ T cells may provide a potential therapy to improve lymphocyte function in HIV-infected individuals.
Upregulation of CTLA-4 by HIV-specific CD4+ T cells correlates with disease progression and defines a reversible immune dysfunction
Daniel E Kaufmann, Daniel G Kavanagh, Florencia Pereyra, John J Zaunders, Elizabeth W Mackey, Toshiyuki Miura, Sarah Palmer, Mark Brockman, Almas Rathod, Alicja Piechocka-Trocha, Brett Baker, Baogong Zhu, Sylvie Le Gall, Michael T Waring, Ryan Ahern, Kristin Moss, Anthony D Kelleher, John M Coffin, Gordon J Freeman, Eric S Rosenberg & Bruce D Walker
Published online: 30 September 2007 | doi 10.1038/ni1515
