CXCR4 and B-cell chronic lymphocytic leukemia: Here, we investigated the expression and inducibility of IL-12 family receptor subunits (IL-23R, IL-12Rβ1, IL-12Rβ2) and the related receptor complexes in recirculating CLL cells, with a focus on CXCR4/CD5-defined fractions: the proliferative fraction (PF; CXCR4<sup>dim</sup>/CD5<sup>bright</sup>; most recently divided, tissue-emigrated cells) and the resting fraction (RF; CXCR4<sup>bright</sup>/CD5<sup>dim</sup>; older, quiescent cells).