In this study, we examined the HCMV DNA in PBLs from our studied OLP patients, and the HCMV DNA in PBLs was significantly higher in OLP patients than in control subjects, while the positive rates of anti-HCMV IgG (past or current infection) and anti-HCMV IgM (current or recent infection) were not different between OLP patients and controls. Here, CD40LG is linked to infection.