The function of CD70 (CD70 molecule, ENSG00000125726) is as follows. Expressed at the plasma membrane of B cells, it is the ligand of the CD27 receptor which is specifically expressed at the surface of T cells (PubMed:28011863, PubMed:28011864, PubMed:8387892). The CD70- CD27 signaling pathway mediates antigen-specific T cell activation and expansion which in turn provides immune surveillance of B cells (PubMed:28011863, PubMed:28011864). {ECO:0000269|PubMed:28011863, ECO:0000269|PubMed:28011864, ECO:0000269|PubMed:8387892}.