Figure 1. CTLL-2 cell proliferation induced by phage-displayed mouse IL-2. 10⁴ cells/well were incubated with serial dilutions of purified phage preparations displaying either mIL-2 or an unrelated scFv antibody fragment (A) and soluble in vitro refolded recombinant mIL-2 (B) during 48h. Phages were diluted to reach equivalent levels of phage-displayed proteins (measured in units/mL in a previous ELISA using the anti-c-myc 9E10 mAb as coating antibody). Alamar blue dye was added to the cells and, after 12h incubation, the absorbances at 540 and 630 nm were measured. (C) In order to assess the effects of neutralizing anti-mIL-2 mAbs in this system, increasing concentrations of purified JES6–1A12, JES6–5H4 and S4B6 mAbs were added during the incubation of a sub-saturating concentration of phage-displayed mIL-2 with the cells. 9E10 was used as a control non-neutralizing mAb recognizing the phage-displayed mIL-2 through the c-myc epitope fused to its C-terminal end.