The three Ig-domain from of inhibitory killer cell Ig-like receptor 1(KIR3DL1,NKB1, nkat3, p70KIR) is a NK cell receptor for polymorphic HLA-B determinant. KIR3DLl recognizes the Bw4 determinant defined by sequence motifs at positins 77-83 of the HLA-B heavy chain. The cytoplasmic tail of KIR, which contains two immunoreceptor tyrosine-based inhibition motifs(ITIMs), mediates inhibitory signal transduction that prevents killer cell-mediated cytotoxicity. A His-tag fusion protein of KIR3DL1 cytoplasmic tail(361-444aa) was overexpressed as insoluble protein aggregates(inclusion bodies). This protein was purified by FPLC gel-filtration chromatography, after refolding of the isolated inclusion bodies in a redox buffer.