In the open access paper here, researchers propose TIGIT as a marker of T cell senescence and exhaustion, also known as anergy, in the aged immune system. Further, this is not just a marker, but also a potential therapeutic target, as an initial test of lowered levels of TIGIT resulted in restoration of some measures of lost function in T cell populations with large degrees of senescence and exhaustion. These two forms of T cell dysfunction are not the same thing, but they do have overlapping features, and seem to be connected in a number of ways. In general, such cells perform poorly and behave badly. They show up to increasing degrees in the aged immune system, and play their part in its inflammatory, weakened state.
Much of the research into immune system aging leads to the conclusion that selectively destroying immune cells is helpful. An old immune system is a zoo of breakage and malfunction: too many senescent and exhausted cells; too many cells uselessly specialized to persistent viruses, particularly cytomegalovirus; autoimmunities of many varieties, outright or subtle, some poorly understood or yet to be recognized; and so forth. These problems are
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