Re: Why are thymic hormones never mentioned in connection with T cell senescenc

There is no simple answer for these questions. Generally, if we talk about
use of hormones in therapy or in prevention of any disease, we have to be
aware of the bystander effects that these molecules have on human organism.
Thymic hormones are shown to have many other functions besides their effect
on T cells (http://content.karger.com/ProdukteDB/produkte.asp?Doi=22082).
Also, although thymus involution is progressive with aging, this organ is
capable of generating T cells throughout the life span. Therefore, use of
thymic hormones for rejuvenating immune system could be just partially
effective depending on the age you start to apply it. Thorough exploration
of thymic hormones' functions is necessary before their introducing as
therapeutics. So far, thymic preparations and some purified factors have
been used as immunomodulators of humoral and cellular immunity in patients
with primary immunodeficiencies, autoimmune, and neoplastic disorders
(http://www.copewithcytokines.de/cope.cgi?key=Thymic%20hormones; http://www.antiaging-systems.com/a2z/thymus.htm). Once again, one must
always think about possible benefits and side effects of such a therapy.

There are very good scientific papers on the topic of thymus and immune
system senescence. Here are two of them in which you can find many
important facts and (some of the) answers to the questions made:

Taub DD, Longo DL. Insights into thymic aging and regeneration.
Immunol Rev. 2005 Jun;205:72-93. Review.

Dixit VD, Yang H, Sun Y, Weeraratna AT, Youm YH, Smith RG, Taub DD. Ghrelin
promotes thymopoiesis during aging. J Clin Invest. 2007 Oct;117(10):2778-90.