Antigen binding specificity (A, B&C) and cytotoxic activity of LaDR5 (D). A: 2 μg/mL DR4 or DR5 was coated and incubated with diluted LaDR5 or TRAIL, by which it was indicated that LaDR5 could bind soluble DR5 specifically other than DR4, while TRAIL could bind both of them in a dose-dependent manner; B: Western blot analysis of LaDR5 to bind antigen. 1: DR5; 2: DR4; 3: Protein Marker. Only in lane 1, a specific line with the molecular weight of about 19kD could be seen, indicating that LaDR5 could bind DR5 specifically; C: Epitope overlapping of LaDR5 and TRAIL to bind DR5 by competing ELISA. Diluted TRAIL was mixed with LaDR5 previously and the mixtures were added to antigen-coated plate. TRAIL could obviously influence the binding of DR5 and LaDR5 in a dose-dependent manner; D: cytotoxic activity of TRAIL or LaDR5 in different tumor cell lines by MTT assay, in which Jurkat seemed to be the most sensitive cell line to LaDR5 as well as TRAIL. Cells were cultured in 96-well flat-bottom plate in triplicates and treated with the indicated concentration of purified LaDR5 or TRAIL. The experimental error is the SD from three independent experiments.