Strain specific FSTL3 expression analysis in homozygous B-hFSTL3 mice by ELISA. Serum collected from wild-type C57BL/6N mice (+/+) and homozygous B-hFSTL3 mice (H/H) were analyzed by ELISA with human-specific FSTL3 ELISA kit. Human FSTL3 was exclusively detectable in homozygous B-hFSTL3 mice but not in wild-type mice.