To characterize the effector phenotype and potential anti-viral role of these QFL T cells during MCMV infection, we examined the expression of KLRG1, an effector marker expressed on cytotoxic, proliferative, and virus-specific T cells,54-56 along with CD44, a marker of antigen experience, on QFL T cells in mice 10 days after infection with MCMV (Figure 4). The gene discussed is CD44; the disease is infection.