GM-CSF-MOBILIZED PERIPHERAL-BLOOD CD34(-STATE BONE-MARROW CD34(+) CELLS IN ADHESION MOLECULE EXPRESSION() CELLS DIFFER FROM STEADY)

To determine the effect of growth factor mobilization on the expressio n of adhesion molecules, we compared CD34(+) progenitor cell (PC) popu lations from steady-state bone marrow (BM) with granulocyte-macrophage colony-stimulating factor (GM-CSF)-mobilized apheresis products (peri pheral blood stem cell (PSC)) using how cytometry, To increase the acc uracy of this analysis, CD34(+) cells were enriched (MiniMACS) before cytometric analysis, A significantly lower expression of very late ant igen-4 (VLA-4), leukocyte function antigen-1 (LFA-1) and LFA-3 were ob served on PSC compared to BM CD34(+) cells, In addition, significantly lower mean fluorescence intensity (MFI) of VLA-4, VLA-5, intercellula r adhesion molecule-1 (ICAM-1), and sialyl Lewis(x) were observed on P SC as compared to BM CD34(+) cells, Significantly higher levels of L-s electin and CD44 expression were observed on PSC as compared to BM CD3 4(+) cells based on frequency and MFI (P less than or equal to 0.05), In addition, the duration of GM-CSF administration or number of prior aphereses had no effect on adhesion molecule expression, These data su ggest that decreased expression of adhesion molecules including VLA-4, LFA-1, ICAM-1 and LFA-3 play a role in PC mobilization. Based on thes e studies, we suggest that PC mobilization occurs as a stochastic proc ess and is associated with the selection of CD34(+) cells with low adh esion molecule expression.