PDCD1 and breast cancer: For example, both α- and β-ARs are expressed on the surface of monocytes and dendritic cells (DCs), which, upon stimulation, promote an immunosuppressive phenotype, whereas blockade of β-AR signaling results in the downregulation of PD-1 and increased production of interferon (IFN)-γ in BC-infiltrating CD4+ and CD8+ T cells 34.