A human monoclonal antibody directed against the human inhibitory killer IgG-like receptor (KIR) with potential immunostimulating and antineoplastic activities. Anti-KIR monoclonal antibody IPH 2101 binds to the KIR receptor expressed on human natural killer (NK) cells, which may prevent KIR-mediated inhibition of NK cells and permit NK cell-mediated anti-tumor cytotoxicity. KIRs are surface glycoproteins that bind to major histocompatibility complex (MHC)/human leukocyte antigen (HLA) class I subtypes on target cells; binding of KIRs inhibits NK cell-mediated cytotoxicity.