Strain specific IL9 expression analysis in homozygous B-hIL9 mice by ELISA. Splenocytes were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hIL9 mice (H/H). The CD4+ T cells were isolated from splenocytes and then Induced into Th2 cells in vitro. Supernatant of Th2 cell culture was analyzed by ELISA with species-specific IL9 ELISA kit. Mouse IL9 was detectable in wild-type mice. Human IL9 was exclusively detectable in homozygous B-hIL9 mice but not in wild-type mice.