Figure 3. Sequence alignment of mouse and human IL-2. Eight discrete segments of mIL-2 covering all the differences between both molecules (selected for partial humanization) are underlined. The first two residues (Ala-Pro, shown in gray) are absent from the phage-displayed molecules. Residues Cys140 and Cys125 (unpaired Cys) in mouse and human IL-2 respectively were replaced by Ser (shaded in gray).