As you might recall, one reason that the immune system declines with age relates to its capacity of cell types. An aged immune system is clogged with useless memory cells, leaving few resources for capable cells to fight new threats. The other reason is the decline of the thymus, source of immune cells:

The immune system undergoes dramatic changes with age - the thymus involutes, particularly from puberty, with the gradual loss of newly produced naive T cells resulting in a restricted T cell receptor repertoire, skewed towards memory cells. Coupled with a similar, though less dramatic age-linked decline in bone marrow function, this translates to a reduction in immune responsiveness

But what if we could regenerate the thymus, restoring it to a vigorous production of new immune cells? That could be one way of pushing out the limits, and making the accumulation of memory cells less harmful at any given age. One of the long-time Fight Aging! readers kindly pointed me to a recent article at Scientist Live on this topic:

Successfully combating illness in elderly individuals can potentially add years to a life. At the centre of this struggle lies an immune system that becomes compromised with age, subsequently leaving the body susceptible to diseases younger bodies would normally keep at bay.

Dr. Claude Perreault and a team of Canadian and Finnish scientists has identified a protein able to stimulate the production of T-cells, the white blood cells involved in the recognition and the elimination of infectious agents.

...

why does the thymus involute early in life so that it leaves older people immunodeficient. For example, thymic atrophy begins as early as one year of age. Progressive thymic involution is responsible for the fact that elderly individuals have very poor thymic function. They produce very little T-Lymphocytes and because of that they are more susceptible to infections, cancer, and autoimmune disease.

We also found that one major characteristic of the thymus found nowhere else in [the] lymphoid organs is the expression of a protein called Wnt4. We hypothesised that Wnt4 had a role in T-Lymphocyte development and that by providing high levels of Wnt4 to hematopoietic progenitor cells we would enhance [production of immune cells]. That is how it began.

We did two series of experiments. In the first set, we induced over-expression of Wnt4 in hematopoietic stem cells and found that compared to mice that received standard cells those that received cells producing high levels of Wnt4 had a bigger thymus and produced 3-4 times more T-Lymphocytes. ... when we knocked out Wnt4 there was thymic atrophy.

Overall, these studies suggest that Wnt4 is necessary for normal T-cell production and that over-expression of Wnt4 is sufficient to improve [production of immune cells]. In the future, we hope to evaluate the best way to give Wnt4 to animals or humans in order to find whether this molecule can be used to treat thymic involution.

An interesting start; I suspect we'll hear more along these lines in the years ahead.

Posted by Reason at August 25, 2008 7:34 PM | TrackBack (0)