MRC1 and infection: Interestingly, the PD-L1 was mostly expressed on the surface of the M1 macrophages (CD86+) during the early infection (1–3 weeks), but not on the CD206+ M2 macrophages, while the PD-L2 was mostly expressed on the CD206+ M2 macrophages during the late stage of infection (Figure 2f,g).