A fully human monoclonal antibody directed against the protein ligand PD-L1 (Programmed Death-1 Ligand 1) with immunomodulating and potential antineoplastic activities. Anti-PD-L1 monoclonal antibody MDX-1105 binds to PD-L1, blocking its binding to and activation of its receptor, PD-1 (Programmed Death 1), which may enhance the T-cell-mediated immune response to neoplasms and reverse T-cell inactivation in chronic infectious disease. PD-L1 is expressed broadly on hematopoietic and parenchymal tissues; PD-1, a transmembrane protein, is a negative regulator of the immune system that limits the expansion and survival of CD8+ T cells.