Pe. Fields et al., B7.1 IS A QUANTITATIVELY STRONGER COSTIMULUS THAN B7.2 IN THE ACTIVATION OF NAIVE CD8(-TRANSGENIC T-CELLS() TCR), The Journal of immunology (1950), 161(10), 1998, pp. 5268-5275
Using a TCR transgenic mouse bred onto a recombinase-activating gene-2
-deficient background, we have examined the influence of B7.1 and B7.2
on activation of naive, CD8(+) T cells in vitro. We found that B7.1 w
as a more potent costimulus than B7.2 for induction of proliferation a
nd IL-2 production by naive CD8(+) T cells. This difference appeared t
o be quantitative in nature, as determined using transfectants express
ing various defined levels of B7.1 or B7.2, or using purified B7.1 or
B7.2 fusion proteins. In contrast to the quantitative differences seen
in stimulation of naive T cells, B7.1 and B7.2 were comparable in the
ir ability to costimulate responses in T cells previously primed in vi
tro. In addition, primed, but not naive, T cells were capable of proli
ferating and producing IL-2 in response to a TCR stimulus alone, appar
ently in the absence of B7 costimulation, Lastly, we found that B7.1 a
nd B7.2 were equivalently capable of driving differentiation of naive
CD8+ T cells into an IL-4-producing phenotype when exogenous IL-4 was
added to the primary culture or to an IFN-gamma-producing phenotype in
the presence of IL-12, These results indicate that signals generated
by B7.1 and B7.2 are qualitatively similar, but that B7.1 is quantitat
ively stronger than B7.2, Further, our results indicate that the activ
ation state of the responding T cell may influence the efficiency with
which the T cell can respond to a costimulatory signal provided by ei
ther B7.1 or B7.2.