last updated April 2013
When memory fails
New findings challenge old assumptions about how the immune system responds to viral invasion
As the ‘enforcers’ of the cellular immune system, one of the main roles of T cells is to kill virus-infected cells. Initially, new T cells are trained to attack specific viral targets. In subsequent encounters with the same intruder, memory T cells will quickly recognize the same target. Both T cell types must first be primed by dendritic cells, which present antigens on the cell surface.
Many subtypes of dendritic cells exist and, although early evidence suggested that memory T cells should be activated by a broader range of dendritic cells than new T cells, recent work by Australian researchers Gabrielle Belz and William Heath reveals that memory cells actually have significantly stricter priming requirements1.
Working with influenza in mice, their results support a model where the immune system is able to replace ineffectual memory cells by favoring the priming of batches of new cells — potentially strengthening response against mutation-prone viruses like HIV.
It is not clear why different dendritic cells stimulate different T cell types, and the researchers hope to extend their findings to clarify this process. “If we can understand the molecular regulation,” says Belz, “it may be possible to target these pathways for vaccine purposes.