This research suggests that some aspects of re-engineering an age-damaged immune system to restore its performance may be easier than expected. It is also supportive of work on immune cell transplant therapies as cancer treatments that has taken place over the past few years, as well as a range of other existing and potential immune therapies:
Researchers have proven for the first time that specific individual cells of the immune system, termed central memory T cells, have all the essential characteristics of adult tissue stem cells. Such cells are capable of perpetuating themselves indefinitely as well as generating diverse offspring that can reconstitute "tissue" function. These findings indicate that it should be possible to fully restore specific immunity to pathogens in patients with a compromised immune system by substitution of small numbers of central memory T cells.
The researchers first established that a high potential for expansion and differentiation in a defined subpopulation, called "central memory T cells," does not depend exclusively on any special source such as bone marrow, lymph nodes, or spleen. This supported but did not yet prove the idea that certain central memory T cells are, effectively, adult stem cells. Further experiments, using and comparing both memory T cells and so-called naive T cells - that is, mature immune cells that have not yet encountered their antigen - enabled the scientists to home in on stem-cell-like characteristics and eliminate other possible explanations.
Step by step, the results strengthened the case that the persistence of immune memory depends on the "stemness" of the subpopulation of T cells termed central memory T cells: Individual central memory T cells proved to be "multipotent," meaning that they can generate diverse types of offspring to fight an infection and to remember the antagonist. Further, these individual T cells self-renew into secondary memory T cells that are, again, multipotent at the single-cell level. And finally, individual descendants of secondary memory T cells are capable of fully restoring the capacity for a normal immune response.
One implication is that future immune-based therapies for cancers and other diseases might get effective results from adoptive transfer of small numbers of individual T cells. "In principle, one individual T cell can be enough to transfer effective and long-lasting protective immunity for a defined pathogen or tumor antigen to a patient. These results are extremely exciting and come at a time when immunotherapy is moving into the mainstream as a treatment for cancer and other diseases. The results provide strong experimental support for the concept that the efficacy and durability of T cell immunotherapy for infections and cancer may be improved by utilizing specific T cell subsets."