Immunologists have identified two bigÂ groups of TÂ cells:Â “helper” CD4+ cells and “killer” CD8+ cells.* The helper cells can produce immune regulatory molecules and promote antibody responses, while the killer cells recognize and destroy virally-infected cells.
A vaccine against a virus that stimulatesÂ only helper CD4+ cells leads to uncontrolled lethalÂ inflammation in mice once the animals are challenged with the virus, a recent paper in Science shows. Emory Vaccine Center director Rafi Ahmed is a co-author.
Senior author Dan Barouch, from Harvard/Beth Israel Deaconess Medical Center, tellsÂ The Scientist that CD4+ cells are like generals directing the battleÂ of the immune system and “if you just have strategic generals and no soldiers,Â it turns out to be worse than having no army at all.” Rebalancing the system with antiviral CD8+ T cells or antibodies helps limit the problems.
The findings mesh with work by Yerkes investigators [Guido Silvestri and colleagues]Â suggestingÂ that HIV vaccines that boost CD4+ cells in gateway mucosal tissues lead to higher rates of infection. In both cases, the lesson is: having more helper CD4+ T cells aroundÂ actually does not help.