An Alternate View of the Aging Immune System
The mainstream view of aging in the adaptive immune system is that too many memory T cells exist, uselessly specialized and using up limited resources that should be devoted to the naive T cells needed to tackle new threats. An alternative (and not mutually exclusive) theory is presented in this paper: that memory cell populations are failing in old age, meaning that acquired immunity vanishes. "Evidence is accumulating that old individuals are more susceptible to infection with organisms to which they were previously immune, indicating that there might be a limit to the persistence of immune memory. The prevailing concept is that defects in memory T-cell populations result from inexorable end-stage differentiation as a result of repeated lifelong antigenic challenge. We discuss here mechanisms that might constrain the persistence of memory T cells and consider whether humans will suffer from memory T-cell exhaustion as life expectancy increases." Whether or not this in fact occurs, the proposed therapies would look much the same as for other immune system issues known to occur with aging: destroy the old, misconfigured, damaged immune cells and replace them with new cells grown from the patient's stem cells.