All:
> In article <8htpr7$ph2$1 at sylvester.vcn.bc.ca>,
> Doug Skrecky <oberon at vcn.bc.ca> wrote:
> > Shortage of circulating naive CD8+ T cells provides
> > insights on immunodeficiency in aging.
> >
> > Blood 95: 2860-2868 2000
> >
> > Abstract:
> >
Surprisingly, the naive T-cell
> > count was lower in CD8+ than in CD4+ subsets at any
> > age, and the oldest individuals were almost completely
> > depleted of circulating naive CD8+ T cells (13 +-4 cells/microL).
This shift from naive to memory T-cells is well-documented in rodents; CR
almost completely prevents it.
> J Clin Immunol 1997 Jan;17(1):85-95
Effect of food restriction on life span and immune functions in long-
lived
Fischer-344 x Brown Norway F1 rats.
Fernandes G, Venkatraman JT, Turturro A, Attwood VG, Hart RW
Department of Medicine, University of Texas Health Science Center, San
Antonio
78284-7874, USA.
Life-long food restriction is known to slow aging and reduce the rate of
occurrence of age-associated disease processes, but the mechanism by
which this
is accomplished is unknown....
Although flow cytometric analyses did not reveal differences for CD4,
CD8, and
Ig+ cells with age, a significant rise in memory T cells (Ox-22low) in
both CD4+
and CD8+ T-cell subset lineage was noted in AL-fed rats at 30 months of
age. In
FR rats, however, only a minimal shift of naive T cells (Ox-22high) to
memory
cells was observed. In FR rats, the observed changes in the naive and
memory
T-cell subsets correlate well with the observed higher levels of the
antiinflammatory interleukin-2 (IL-2) and lower levels of the
proinflammatory
cytokines such as IL-6 and tumor necrosis factor-alpha. The ability of
food-restricted animals to recall antigens was lower compared to their
age-matched controls, though the proliferative response to T-cell mitogen
Con A
and superantigen staphylococcal enterotoxin B was higher. These findings
indicate that food restriction may selectively act to maintain a lower
number of
antigen-induced memory T cells with age, thereby maintaining the
organism's
ability to produce higher levels of IL-2 with age. In summary, the
increased
cell-mediated immune function noted in aged FR rats appears to be due to
the
presence of a higher number of naive T cells, which are known to produce
elevated levels of the antiinflammatory cytokines, which may in part be
responsible for reducing the observed age-related rise in disease.
PMID: 9049789, UI: 97202262
-Michael
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