Activating KIR/HLA-I combinations as a risk factor of adult B-ALL.

B-cell acute lymphoblastic leukemia (B-ALL), the most predominant type of ALL, is less common and incurable among adults. Regarding the pivotal role of NK cells in immune surveillance against hematological malignancies, studying the effective factors in regulating their function, particularly KIRs as the most important NK cell receptors and HLA-I molecules as their main ligands, is of importance. Since NK responses against malignant lymphoblasts are influenced by KIR signals, we did a case-control study on 154 adult patients with B-ALL and 181 healthy controls to investigate the correlation of KIR/HLA-I combinations with susceptibility to B-ALL in Iranians. The genotyping of KIR genes and HLA-I alleles was performed by PCR-SSP with 11 and 9 primer pairs, respectively. Our data revealed an increased frequency of activating (a)KIRs and aKIR/HLA-I combinations in our patients: KIR3DS1 (p = 0.009, OR = 1.81), Bx genotype (p = 0.038, OR = 1.81), KIR3DS1(+)/HLA-Bw4Thr80 (+) (p = 0.004, OR = 3.61), and KIR3DS1(+)/HLA-B Bw4(+) (p = 0.037, OR = 1.76). The presence of inhibitory (i)KIRs in the absence of their cognate HLA-I ligands was also more frequent among the patients. However, the frequency of inhibitory combinations was more common in controls: KIR2DL1(+)/HLA-C2(+) (p = 0.027, OR = 0.57), KIR2DL2/3(+)/HLA-C1(+) (p = 0.004, OR = 0.5), and KIR3DL2(+)/HLA-A3/A11(+) (p = 0.0012, OR = 0.46). To sum up, the less inherited iKIR/HLA-I combinations might make individuals more susceptible to B-ALL because of inefficient education of NK cells.