Strain specific TNFRSF11B expression analysis in wild-type C57BL/6 mice and homozygous humanized B-hTNFRSF11B mice by ELISA. Serum was collected from wild-type C57BL/6 mice (+/+) and homozygous B-hTNFRSF11B mice (H/H) (n=3, 6-week-old). Protein expression level of TNFRSF11B was analyzed by ELISA. Mouse TNFRSF11B was only detectable in wild-type C57BL/6 mice. Human TNFRSF11B was exclusively detectable in homozygous B-hTNFRSF11B mice