Strain specific CTLA4 and IL2RA expression analysis in homozygous B-hCTLA4/hIL2RA mice by FACS. Splenocytes were collected from wild type (+/+) and homozygous B-hCTLA4/hIL2RA mice (H/H,H/H) stimulated with anti-mCD3ε antibody in vivo, and analyzed by FACS with species-specific anti-CTLA4 or anti-IL2RA antibodies. Mouse CTLA4 and IL2RA were detectable in wild type mice. Human CTLA4 and IL2RA were exclusively detectable in homozygous B-hCTLA4/hIL2RA mice but not in wild type mice.