We expressed humanized (Hm-E16) and chimerized (Ch-E16) E16 in HEK-293 cells, and purified them from supernatants by affinity and size-exclusion chromatography (data not shown). The affinity was analyzed by surface plasmon resonance using purified antibody in the solid phase. Mouse E16 binds DIII with an affinity of 3.4 nM and a half-life of 3.9 min. The affinity of the Ch-E16 and Hm-E16 was similar with K D ranging from 7.1 to 21 nM (Fig. 4c) . Hm-E16, Ch-E16, and the parent E16 all had similar PRNT 50 values (Fig. 4d) .