PDCD1LG2 and infection: At FACS analysis, all five cell lines were negative for PD-L2; however, after HV-HP infection, three cell lines (N87, SNU-1 and SNU-16) showed significantly increased PD-L2 expression compared to their uninfected counterparts (P<0.05; Figure 3D; Supplementary Figure S1), with N87 showing the highest ΔMFI level.