I was pleased to get my results from my Telomere testing this week showing I have the immune system of a teenager.
It is known that as we age, our ability to respond to cancer and immune challenges decreases as a function of our decreasing reserve of Naive T-Cells (CD45+ CD28+ CD20-)
The biggest declines occur in the first year of life and are also rapid until puberty.
The average telomere length of my Naive T Cells is 9.2, which is quite high
Here is a nomogram of average telomere lengths by age for these Naive T-Cells
–from Aubert et al, “Collapse of Telomere Homeostasis in Hematopoietic Cells Caused by Heterozygous Mutations in Telomerase Genes”. PLOS Genetics, May 17, 2012
This chart and my own results are both from REPEAT Diagnostics, based out the University of British Columbia.
Interestingly, Naive T-Cells can be further subdivided into “good cops” and “bad cops” as in Lethal Weapon. The good ones, present in younger, healthier individuals, are naive and ready to go, like bat guano crazy Mel Gibson’s Martin Riggs character. The bad ones are like Danny Glover’s character, Roger Murtaugh, hiking up their pants and counting the days to retirement while muttering “I’m too old for this $h!t”. The difference is in how many TRECs they possess and whether the CD31 receptor is retained:
The aging process also changes the quality of naïve T cells. There are two subsets of naïve (CD62L+CD45RA+) CD4+ T cells in the peripheral blood of humans, defined by the presence or absence of CD31 (PECAM-1) (Kimmig et al., 2002). CD31+ naïve CD4+ T cells may resemble recent thymic emigrants, with a high content of T cell receptor excision circles (TRECs), while CD31− naïve CD4+ T cells have a lower TREC content and a restricted T cell repertoire (TCR).
— from http://journal.frontiersin.org/article/10.3389/fimmu.2013.00136/full
Interestingly, another study looked at these PECAM-1 or CD31 subclasses of naive T-cells and found that even children had lost most of their best cops as defined by this marker. And within two adult individuals, the good cop naive t-cells had higher telomerase activity than the bad cop naive t-cells:
from – http://www.ncbi.nlm.nih.gov/pubmed/17935071
For a nice review article of immune senescence as a marker of aging (although I think it is also the cause) read this reference: http://journal.frontiersin.org/article/10.3389/fimmu.2013.00136/full
For an interesting blog about immune aging and a link to the the video I did on “AIDS and Aging”, check out this blog.