Old People Have Old T Cells, and They Don't Work Very Well

[Guest guest]

Old T Cells Cripple Immune Function In The Elderly

12/20/2004

Source: Journal of Experimental Medicine

T cells are the weakest link in the immune systems of older people,

based on a report by Eaton and colleagues in the December 20 issue of

The Journal of Experimental Medicine. The authors show that old

CD4 " helper " T cells cannot provide the stimulatory signals to B

cells that prompt them to make antibodies. Old and young B cells,

however, are equally effective if helped by young CD4 T cells. The

authors think this may help explain why immunizations are less

effective in the elderly.

B cell activation and antibody production are known to be impaired

with age in both mice and humans, but it was not clear whether this

defect is intrinsic to B cells or is a by-product of declining CD4 T

cell helper functions.

Eaton and colleagues transferred young or old CD4 T cells into mice

lacking their own CD4 T cells to determine which cells are

responsible for the age-related decline in B cell function. They show

that B cell activation and antibody production can be restored in old

mice if they are infused with young CD4 T cells prior to

immunization. On the flip side, young mice infused with old CD4 T

cells developed antibody defects, even though their B cells were

young.

In other words, old B cells function like young ones if provided with

signals from young helper T cells.

While the mechanism is not completely clear, the authors show that

old T cells can travel to the right location in the spleen of the

mice, but have fewer of the surface proteins that send stimulatory

signals to B cells.