Inhibitory effects of I3C on cell viability of HTLV-1-infected T-cell lines and primary ATLL cells. Cell lines and PBMC were incubated in the presence of various concentrations of I3C for 72 h and 24 h, respectively, and viability of the cultured cells was measured by WST-8 assay. Relative viability of cultured cells is presented as the mean determined on cell lines (A) and PBMC from healthy controls and ATLL patients (B) from triplicate cultures. A relative viability of 100% was designated as total number of cells that grew in 72-h cultures in the absence of I3C. HUT-102, MT-4 and TL-OmI are HTLV-1-infected T-cell lines; Jurkat, MOLT-4 and CCRF-CEM, uninfected T-cell lines used as controls. Data are mean ± SD of triplicate experiments.