During activation T cells are thought to change their patterns of gene expr
ession dramatically. To find out whether this is true for T cells activated
in animals, the patterns of genes expressed in resting T cells and T cells
8 and 48 hr after activation were examined by using Affymetrix gene arrays
. Gene arrays gave accurate comparisons of gene expression in the different
cell types because the expression of genes known to vary during activation
changed as expected. Of the approximately 6,300 genes assessed by the arra
ys, about one-third were expressed to appreciable extents in any of the T c
ells tested. Thus, resting T cells express a surprisingly large diversity o
f genes. The patterns of gene expression changed considerably within 8 hr o
f T cell activation but returned to a disposition more like that of resting
T cells within 48 hr of exposure to antigen. Not unexpectedly, the activat
ed T cells expressed genes associated with cell division at higher levels t
han resting T cells. The resting T cells expressed a number of cytokine rec
eptor genes and some genes thought to suppress cell division, suggesting th
at the state of resting T cells is not a passive failure to respond to exta
nt external stimuli.