Engraftment of β2m^−/− NOD/SCID mice and in vivo homing by human CD34⁺ cells is enhanced by CD8⁺ cells.

(A) Mice were injected with CD34⁺ alone, CD34⁺ and CD8⁺, or CD34⁺ and CD4⁺ cells. Measurements of the level of human CD45⁺ cells in the bone marrow were then measured by flow cytometry at 6 weeks after injection. Cells from an individual cord blood source were divided and transplanted, and the outcome of engraftment of CD34⁺ alone was compared to that of CD34⁺ and CD8⁺ and to that of CD34⁺and CD4⁺ cells. Transplantations were performed in duplicate; experiments using cells from the same donor source are linked by dashed lines. (B-C) Fluorescently labeled CD34⁺ cells, alone or mixed with CD8⁺ or CD4⁺ cells from the same donor, were injected intravenously into mice from the same litter. Nine hours following the injection, the mice were killed and the numbers of labeled cells in the bone marrow (B) or spleen (C) were measured by flow cytometry. Each point represents a single mouse. The solid bars represent mean values. (D) Transmigration of CD34⁺ cells alone, CD8⁺or CD4⁺ alone, or CD34⁺ cells in the presence of CD8⁺ or CD4⁺ cells was measured by cell counting and flow cytometry. A BMEC-coated Transwell with SDF-1α as the chemotactic agent was used. Data are represented as the means of 4 independent experiments; error bars represent SEMs. See theBlood website for Figures S1, supplemental to panel B, and S2, supplemental to panel A; go to the Supplemental Materials link at the top of the online article.