Analysis of the expression of the γc chain and JAK3 in normal human CD34+ cells and effects of anti—IL-15 mAb. Confocal microscopy on overlay pictures (original magnification, × 63) shows the presence of γc chain (green) and JAK3 (red) in BM, MPB, and CB CD34⁺ cells. Yellow staining demonstrates that the 2 molecules almost totally colocalize in BM (A) and MPB (B), but not in CB CD34⁺ cells, where there is only a partial overlapping of the 2 molecules (C). Side-side pictures of the previous picture shows that the expression of γc (totally) and JAK3 (partially) is inhibited after overnight treatment with neutralizing anti—IL-15 mAb in BM (Ai) but not in MBP (B1) and CB (C1) hematopoietic precursors. However, in MBP precursors, anti—IL-15 treatment prevents colocalization of the JAK3 and the γc chain in 30% of the cells in the field. These data are representative of 3 different experiments.