Strain specific DR4 expression analysis in homozygous B-hDR4 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hDR4 mice (H/H) stimulated with or without anti-mCD3ε in vivo (7.5 μg/mice, stimulation for 24 hours, i.p.), and analyzed by flow cytometry with species-specific anti-DR4 antibody. Human DR4 was detectable in homozygous-stimulated B-hDR4 mice but not in wild-type mice.