Thy-1 expression within CD34⁺CD38⁺ progenitor and CD34⁺CD38⁻ stem cell compartments in normal and 5q− syndrome BM. CD34-enriched normal (A) and 5q− (B, patient no. 6) BM cells were stained with monoclonal antibodies (MAbs) against CD34, CD38, and Thy-1 or irrelevant isotype control Abs (“Purification of BM cell populations”). Left panels show expression profiles for already CD34-enriched cells, with the size of the CD34⁺CD38⁺ and CD34⁺CD38⁻ populations given as percentages of total MNCs. Shown are also the gates for CD34⁺CD38⁺ and CD34⁺CD38⁻ cells used for sorting and for further investigation of Thy-1 expression (middle panels). Dotted lines represent the negative isotype control and solid lines the specific Thy-1 expression. Note that Thy-1 expression is much higher in CD34⁺CD38⁻ than in CD34⁺CD38⁺ cells for both healthy and 5q− subjects. Sorted CD34⁺CD38⁻Thy-1⁺ candidate HSCs and CD34⁺CD38⁺Thy-1⁻ candidate progenitors were analyzed by FISH for the 5q deletion. Normal CD34⁺CD38⁻Thy-1⁺ cells (A) show 2 green and 2 red signals, whereas CD34⁺CD38⁻Thy-1⁺ cells with 5q deletion (B) show 2 green and 1 red signal (right panels). Bars in the FISH pictures represent 10 μm.