CX3CR1 and infection: We gated on CD45+ (Blood) Ly6Chigh CX3CR1-GFP+ monocytes, as well as CD45+ (Blood) Ly6Clow CX3CR1-GFP+ monocytes, to examine PD-L2 expression on these cells at 6 weeks post-infection, when PD-L2+ cells can be found in the blood (Figure 5F).