Expression of IL-15Rα on different PBMC cell subsets. Histograms of IL-15Rα staining are shown for 2 long-term post-IM patients studied 5 and 14 years after infection (left panel) and for 2 healthy EBV carriers (right panel); in each case, PBMCs were costained with IL-15Rα mAb and with cell subset-specific markers. From top to bottom, panels show IL-15Rα staining profiles on gated populations of CD8⁺ T cells, CD4⁺ T cells, CD56⁺ NK cells, CD19⁺ B lymphocytes, and CD14⁺ monocytes. The shaded histograms represent staining of the same gated population with a mouse isotype control. These results are representative of those obtained in experiments on 11 post-IM patients and 9 healthy carriers.