Fig. 1From: Immune response in breast cancer brain metastases and their microenvironment: the role of the PD-1/PD-L axisImmunohistochemical positive control (original magnification × 400). a Programmed cell death protein 1 receptor (PD-1): lymph node (germinal center in follicle). b Programmed cell death protein 1 receptor ligand (PD-L1): skeletal muscle. c PD-L2: lymph node (subcapsular sinus)Back to article page