CD28 and cytomegalovirus infection: The results showed that activation of PBLs with CD3/CD28 stimulation reduced T-cell killing of GC cells upon HCMV infection (Mean ± SEM: 46,676 ± 3,403 in the AD169 infected group vs. 27,786 ± 1,552 in the uninfected group, P < 0.001) (Fig. 2A).