KIR Gene and HLA-Cw Mismatches Affect on NK Cell Killer Activity

The KIRs were knew as natural killer (NK) cell inhibitory receptors with specificity for HLA molecules on their cellular targets. We investigated NK cell activation on the number of matches between cell killer immunoglobulin-like receptor (KIR) gene and HLA-Cw, and the level of inhibitory KIRs expressed on NK cell surface and the cytotoxicity of NK cell against AML leukemic cells in vitro. NK cell were isolated and purified from 27 healthy donors by isolation kit, Target cells were blasts derived from bone marrow of 30 patients with AML.Inhibitory KIRs expression knew as CD158a, CD158b was analyzed by flow cytometry to estimate the percentage of NK cells that could be inhibited by the HLA-Cw ligands..KIR and HLA gene typing were performed by PCR –SSP. from donors and patients respectively. NK cytotoxicity against AML leukemic cells demonstrated by MTT which showed the correlation between NK cytotoxicity and the number of KIR/HLA matches. the NK-susceptible K562 cell line which lacks HLA class I expression, was used as a positive control target in all cytotoxicity assays, autologous non-NK cell was used as negative control target cell. the cytotoxicity assays was performed in E:T 50:1 20:1 10:1 5:1 2.5:1. Results demonstrated the less number of KIR/HLA-Cw matches, the more NK cells are activated..0 match of NK cell/target cell KIR/HLA-Cw, cytotoxicity was (50.66±8.40)%,1 match and 2 matches were (38.28±6.71)%, (19.74±4.15)%, F=20.226, P<0.001. NK cells expressed KIRs also had relationship with cytotoxicity, inhibitory KIRs expressed >50%, the cytotoxicity is 10%, inhibitory KIRs expressed 20%–50%, the cytotoxicity is 20%, inhibitory KIRs <25%, the cytotoxicity is 55%, F=16.276,p<0.001. Therefore these data indicate NK cell kill AML leukemic cells mechanism follow KIR/HLA-Cw mismatch theory, the level of inhibitory KIRs expressed on NK cell surface showed the percentage of NK cells that could be inhibited by the HLA-Cw ligands. Key words: KIR NK cell CD158 HLA-Cw