IL-15 increases IFN-γ production by alloreactive T cells in vitro. Wild-type B6 splenocytes (1 × 10⁸) were primed in vivo in allogeneic (wt B6D2F1, n = 4) or syngeneic (wt B6, n = 1) hosts for 6 days. Splenocytes were then harvested and restimulated in vitro with irradiated naive B6D2F1 splenocytes for 24 or 72 hours. IFN-γ production by allogeneic- or syngeneic-primed splenocytes in the presence of PBS, or 10 ng/mL or 100 ng/mL rm IL-15 is expressed as the mean ± SE of triplicate cultures. ND indicates not detectable.