Hbz supports immortalized T-lymphocyte proliferation in culture. (A) 10³ MT-1 and stable MT-1 lentiviral- (V1-V5) infected cells, (B) PBLACH and stable PBLACH lentiviral- (V4 or V5) infected cells, and (C) PBLHTLV-1 and PBLHTLV-1ΔHBZ cells were plated in normal growth medium in 96-well plates and MTS assays were performed on triplicate wells at 24-hour intervals for a total of 5 days. The average absorbance numbers are plotted and error bars denote SD. * denotes the significant difference in proliferation in Hbz-specific shRNA transduced cells or HTLV-1ΔHBZ–infected cells compared with controls or wild-type infected cells. Statistical significance was determined by ANOVA followed by Tukey test.