Antibody staining
SECONDARY
After deparaffinization and antigen retrieval using Dako Target Retrieval Solution at pH 9 (S236784-2, Agilent) in a water bath (96 °C for 30 min), 3-µm tissue sections were encircled with a Dako Pen and incubated with SuperBlock (37515, Thermo Fisher Scientific) at room temperature for 45 min and then with FcR Blocking Reagent (130-092-575, Miltenyi) at room temperature for 1 h (1:100 in PBS/1% BSA buffer). After three washes (8 min each) in PBS/0.2% Triton X-100 (PBS-T), the PD-L1 antibody was diluted in PBS/1% BSA buffer and incubated at 4 °C overnight. The next day, the slides were washed three times (8 min each) in PBS-T, and secondary anti-rabbit antibody (3175002G, Standard BioTools) was diluted in at 1:500 in PBS/1% BSA buffer and incubated at room temperature for 2 h. After three washes (8 min each) in PBS-T, metal-tagged antibodies (list in Supplementary File Table 