To investigate the role of T-bet in governing S1PR5 expression in vivo, we cotransferred congenically distinct naive OT-I transgenic CD8+ T cells specific for OVA (OVA257–264) and T-bet–deficient OT-I T cells (OT-I Tbx21−/−) into naive C57BL/6 mice before infection with a recombinant strain of HSV-expressing OVA (HSV-OVA). The gene discussed is S1PR5; the disease is infection.