KIR3DL1 and classic Hodgkin lymphoma: The analysis of HLA-KIR combinations showed that cHL patients with a positive iPET-2 scan had higher frequencies of the activating KIR genes, KIR2DS1 and KIR2DS2, combined with the presence of their specific ligands C2 and C1, respectively (KIR2DS1/HLA-C2: 66.7 vs. 35.3 %, p = 0.03; KIR2DS2/HLA-C1: 63.3 vs. 20.6 %, p = 0.004).