Expression of IL-12Rβ2 in normal plasma cells. (A) IL-12Rβ2 surface expression in PPCs generated in vitro (i,ii) or sorted from tonsils (iii,iv), as assessed by flow cytometry using the BD mAb. Open profile represents IL-12Rβ2 staining; dark profile, isotype-matched mAb staining. (B) IL-12Rβ2 surface expression in CD138+ PCs purified from normal BM (i,ii) or tonsil (iii,iv), as assessed by flow cytometry using the BD mAb. Open profile represents IL-12Rβ2 staining; dark profile, isotype-matched mAb staining. (C) Up-regulation of IFN-γ production in PPCs generated in vitro on incubation with medium (□) or hrIL-12 (■) for 48 hours, as assessed by flow cytometry. Results represent median IFN-γ+ cells plus or minus SE from 4 different experiments.