Evaluation of PD-1, PD-L1 by flow cytometry. The following monoclonal antibodies directed against cell surface antigens of human are used: anti-PD-1, anti-PD-L1, anti-PD-L2, anti- cluster of differentiation (CD) 3, anti-CD4, anti-CD8, anti-CD14, anti-CD16, anti-CD56, anti-CD19, anti-CD20.