CD9 is expressed on CD34⁺, CD19⁺, and CD41⁺ cells, but not on GPA⁺ erythroid precursor cells.

Low-density cells were isolated from human bone marrow, stained with either CD34–PerCP-, CD19–PE-, CD41–PE-, or GPA-FITC-conjugated mAbs and were analyzed by multicolor flow cytometry. An R1 region was drawn by selecting the lymphomononuclear cells and was used for gating. The quads were set up on the isotype-matched controls dot plot. Plots shown are for one experiment representative of 10 performed using different low-density mononuclear bone marrow samples.