KIR3DL1 and systemic sclerosis: An epistatic interaction was detected between KIR3DL1 and HLA-Bw4 in the SSc meta-analysis cohort, such that fewer KIR3DL1+ SSc patients carried an appropriate HLA-Bw4 ligand for this inhibitory receptor (67.7%) relative to KIR3DL1+ controls (72.2%, pint = 0.02); accordingly, the protective association of HLA-Bw4 alleles with SSc was seen only in KIR3DL1+ individuals (OR = 0.77, p = 2.0 × 10−5; Table 4).