The aged immune system begins to fail at its job for a variety of reasons that seem to have more to do with its evolved structure and control systems than with the outright incapacity of immune cells, or the inability to generate more immune cells. The immune system evolved to work very effectively in younger life, and that comes at the cost of controlling processes that fall down badly in the long term.

A small reserve of memory cells is needed to respond effectively to previously encountered threats - one reserve per threat. The more threats you have encountered, the more cells become devoted to memory; eventually you don't have enough naive T cells left to mount any sort of effective defense.

Given the capabilities that remain in the body, an aged immune system could, in theory, get up to fight and fight well - but it doesn't. That shortcoming may be addressed by selectively manipulating the system and its cells, however. For example, in recent years researchers have demonstrated that we can (a) intervene via modern medicine to expand the population of useful immune cells, or (b) destroy the accumulation of useless immune cells and thereby immediately free up space so that the body creates more useful immune cells, or even (c) wipe out and recreate the entire immune system as a fresh start, which works to cure autoimmune diseases in which immune cells run amok and attack the body.

I noticed a research release today that discusses the identification of another potential source of useful cells in the aged immune system, cells normally left inactive thanks to the evolved control systems that focus on early life at the expense of later life. The researchers show that these cells can be activated for duty:

Professor Arne Akbar of UCL (University College London), who led this research, explains "Our immune systems get progressively weaker as we age because each time we recover from an infection a proportion of our white blood cells become deactivated. This is an important process that has probably evolved to prevent certain cancers, but as the proportion of inactive cells builds up over time our defences become weakened. What this research shows is that some of these cells are being actively switched off in our bodies by a mechanism which hadn't been identified before as important in ageing in the immune system. Whilst we wouldn't want to reactivate these cells permanently, we have an idea now of how to wake them from their slumber temporarily, just to give the immune system a little boost."

...

When the researchers blocked this newly identified pathway in the lab they found that the white blood cells appeared to be reactivated. Medicines which block this pathway are already being developed and tested for use in other treatments so the next step in this research is to explore further whether white blood cells could be reactivated in older people, and what benefits this could bring.

I see it as a good sign that there are a range of different potential lines of research that might lead to varying degrees of immune system rejuvenation, temporary or otherwise. Variety and competition are signs of a healthy field of medicine.

Source:
http://www.longevitymeme.org/newsletter/latest_rss_feed.cfm