KIR3DL1/S1 allele-level analysis indicated that low-expressing KIR3DL1/S1 alleles in combination with KIR3DS1 increased the risk of developing Behçet disease (KIR3DL1<sup>LOW</sup>/KIR3DS1: <i>p</i> = 0.0004, <i>Pc</i> = 0.0040, OR 2.47, 95% CI 1.43-4.25), whereas high-expressing KIR3DL1/S1 alleles in combination with a null-expressing KIR3DL1 reduced the risk of disease (KIR3DL1<sup>HIGH</sup>/KIR3DL1<sup>NULL</sup>: <i>p</i> = 0.0035, <i>Pc</i> = 0.0350, OR 0.53, 95% CI 0.33-0.87).
We tested whether KIR-regulated mechanisms contribute to BD by testing for association of KIR3DL1/KIR3DS1 genotypes with disease in 1799 BD patients and 1710 healthy controls from Turkey, as well as in different subsets of individuals with HLA-type-defined ligands for the KIR3D receptors.