Blockade of CD257 induced the regression of leukemic cells from TCL1×BAFF-Tg mice grown in vitro and in BAFF-Tg mice. (A) In vitro viability of CD3⁻CD5⁺ cells from TCL1-Tg mice was examined by trypan blue exclusion in absence or presence of 200 ng/mL rhCD257 and absence or presence of 200 μg/mL decoy receptor CD268-Fc (n = 3). (B) BAFF-Tg mice inoculated with leukemic cells were injected with 200 μg of decoy receptors CD269-Fc or CD268-Fc. Peripheral CD3⁻CD5⁺ cell counts were determined 5 days after treatment with decoy receptors. Values represent relative mean ± SD CD3⁻CD5⁺ cell counts of treated mice compared with normalized actual CD3⁻CD5⁺ cell counts of untreated mice (n = 3 mice per each treatment group; each experiment was done in triplicate).