Visualization of PD-l1-positive and PD-1-positive immune cell contact in the breast cancer microenvironment

Functioning of the PD-1/PD-L1 immune checkpoint in the microenvironment of breast cancer may lead to the tumor escape from the immune response. However, it is unknown how often PD-L1 binds to PD-1 in breast cancer patients, which PD-L1-positive cells are predominantly involved in the interaction, and what prognostic significance it has. The objective of the study was to assess the frequency of co-location of PD-1/PD-L1- positive cells in the microenvironment of breast cancer as well as to determine the population of these cells. Material and Methods. The study included 25 patients with invasive breast carcinoma. Interaction between cells carrying the PD-1 receptor and the PD-L1 ligand in the tumor microenvironment were visualized using multiplex TSA (tyramide signal amplification)-modified immunohistochemistry. Participation of M1 macrophages (CD68+CD163-CD3-CKAE1/3-), M2 macrophages (CD68+/-CD163+CD3-CKAE1/3-), lymphocytes (CD68- CD163-CD3+CKAE1/3-) and other immune cells in these interactions was assessed.