Cell adhesion molecule expression on CD34⁺ cells in grafts and time to myeloid and platelet recovery after autologous stem cell transplantation

The relationship between cell adhesion receptor expression on CD34⁺ cells in stem cell grafts and the time to neutrophil and platelet recovery after autologous stem cell transplantation (ASCT [n = 25]) was studied with granulocyte/monocytecolony stimulating factor (GM-CSF)-mobilized peripheral blood stem cells (PBSCs) and steady-state bone marrow (BM) harvests. Cell adhesion receptor expression was analyzed using flow cytometry after CD34⁺ cell enrichment. Significantly higher expression of L-selectin and CD44, and significantly lower expression of VLA-4, LFA-1, ICAM-1, Sialyl Lewis(x), Sialyl Lewis(A), and Thy-1 were observed on PBSCs compared with BM CD34⁺ cells. The log of the number of reinfused CD34⁺ cells, colony forming units granulocyte/macrophage (CFU-GM), and CD34⁺ cells coexpressing VLA-4, VLA-5, LAF-1, Mac-1, LFA-3, or CD38 but not ICAM-1, Sialyl Lewis(x), Sialyl Lewis(A), or Thy-1 correlated with the time required to reach an absolute neutrophil count (ANC) of ≤0.5x10⁹/L. In addition, the log of the number of CD34⁺ L-selectin⁺ and CD34⁺CD44⁺ cells reinfused after ASCT correlated better with the time required to reach an ANC of ≤0.5x10⁹/L than did the log of the number of CD34⁺ cells or CFU-GM reinfused. The log of the number of reinfused CD34⁺ cells, CFU-GM, and CD34⁺ cells coexpressing CD44, L- selectin, VLA-5 Mac-1, or CD38, but not VLA-4, LAF-1, ICAM-1, LAF-3, Sialyl Lewis(x) Sialyl Lewis(A), or Thy-1, correlated with the time required to reach a platelet count of >20x10⁹/L. Thus, L-selectin or CD44 may play an important role in the homing of progenitors after ASCT. In addition, the higher proportion of CD34⁺L-selectin⁺ or CD34⁺CD44⁺ cells in leukapheresis products may provide one explanation for the more rapid hematologic reconstitution observed after PBSC transplantation.