ATL cell culture supernatants contain an antiapoptotic activity mediated by I-309.
BW5147C thymoma cells were treated with dexamethasone (DEX; 62.5 nM) to induce apoptosis (BW5147C/DEX cells) and incubated with increasing dilutions of ATL and control culture supernatants. Cell viability was assessed by MTT assays. Additional cell survival was calculated as described in “Materials and methods.” (A) Antiapoptotic effect of 4 ATL culture supernatants (PaBe, ♦; Champ, ▪; JuanaW, ▴; StEd, ■) in the BW5147C/DEX cells. MT-2 (×) and Jurkat (●) cell culture supernatants served as negative controls. (B) Abrogation of the antiapoptotic effect of the JuanaW cell culture supernatant in BW5147C/DEX cells by the addition of pertussis toxin (2.5 ng/mL) ♦, without pertussis toxin (PT); ▪, with PT. (C) Antiapoptotic capacity of purified I-309 and its susceptibility to pertussis toxin inhibition. The BW5147C/DEX cells were incubated with various concentrations of purified I-30950 in the presence (▪) and absence (♦) of pertussis toxin. (D) Neutralization of the antiapoptotic I-309 effect by monoclonal anti–I-309 antibodies. BW5147C/DEX cells were cultivated in the presence of undiluted ATL supernatant from JuanaW and serial dilutions of anti–I-309 antibodies (♦) or a control antibody (anti-IgG1, ▪). Results represent 3 to 6 independent MTT assays (except for C where only 2 experiments could be done due to limited amounts of purified I-309 protein).
