Modulation of VLA-4 and L-selectin expression on normal CD34+ cells during mobilization with G-CSF.
We have evaluated the immunophenotype, functional activity and clonogenic potential of CD34+ cells from peripheral blood (PB) of normal donors before and after 4 and 6 days of G-CSF administration. The percentage and absolute number of CD34+ cells significantly increased at days 4 and 6 of G-CSF administration, compared to the steady-state level (P < 0.0001). Two-colour fluorescence analysis showed, at days 4 and 6, a lower proportion of CD34+/c-kit+ compared to the steady-state level (P < 0.0001), but a similar expression of CD13, CD33, CD38, HLA-DR and Thy-1 antigens on CD34+ cells. The expression of adhesion molecules on CD34+ cells revealed a significant reduction of CD11a (P = 0.009), CD18, CD49d and CD62L (P < 0.0001) at days 4 and 6, compared to the baseline level. Three-colour staining showed a reduction of the more immature compartment (34+/DR-/13-) and an increase of the more differentiated compartment (34+/DR+/13+). Downregulation of VLA-4 during mobilisation was seen almost exclusively on more committed cells (34+/13+); downregulation of CD62L, on the contrary, was observed on both early progenitors (34+/13-) and more committed cells (34+/13+). The expression of 34+/VLA-4+ decreased on both c-kit+ and c-kit- cells, while the expression of 34+/62L+ decreased on the c-kit+ cells only. In vivo administration of G-CSF reduced the adherence capacity of CD34+ cells to normal BM stroma; in vitro incubation with SCF or IL-3 enhanced the expression of CD49d on CD34+ cells, while GM-CSF reduced the expression of CD62L. SCF was the only cytokine able to induce a significant increase of CD34+ cell adherence to preformed stroma. Pre-incubation with the blocking beta2 integrin monoclonal antibody caused a reduction of CD34+ cell adherence. In conclusion, the decrease of CD49d expression on mobilized CD34+ cells correlates with a poor adhesion to BM stroma; CD34+ cells incubated in vitro with SCF showed, conversely, a higher expression of CD49d and a greater adherence capacity on normal preformed stroma.
Dipartimento di Biotecnologie Cellulari and Ematologia, Università, La Sapienza, Rome, Italy.
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Bellucci
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De Propris
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Buccisano
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Lisci
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Leone
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Tabilio
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de Fabritiis
D015703:Antigens, CD; D018952:Antigens, CD34; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D019650:Hematopoietic Stem Cell Mobilization; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D016130:Immunophenotyping; D039041:Integrin alpha4beta1; D016023:Integrins / Q000096:biosynthesis*; D019041:L-Selectin / Q000096:biosynthesis*; D016201:Receptors, Lymphocyte Homing / Q000096:biosynthesis*
D015703:Antigens, CD; D018952:Antigens, CD34; D039041:Integrin alpha4beta1; D016023:Integrins; D016201:Receptors, Lymphocyte Homing; D019041:L-Selectin; D016179:Granulocyte Colony-Stimulating Factor