Effect of interleukin-7 on the in vitro development and maturation of monocyte derived human dendritic cells

We have compared the cell phenotype and functional properties of monocyte/macrophage derived dendritic cells (DCs) obtained by culture of human adherent peripheral blood mononuclear cells (PBMCs) in medium containing granulocyte macrophage colony stimulating factor (GM-CSF) either alone (GM-CSF-DCs), or in combination with interleukin (IL)-4 (IL4-DCs) or IL-7 (IL7-DCs). The cell surface phenotype of GM-CSF-DCs and IL-7-DCs was characterized by a high expression of major histocompatibility complex (MHC) class I and II, CD80, CD86 and CD40. In contrast to 'classical' IL-4-DCs, these two types of DCs expressed CD14 and a CD21-like molecule detected by two out of four CD21-specific monoclonal antibodies (MoAb) tested. The same pattern of reactivity with CD21 specific antibodies was observed in freshly isolated adherent PBMCs but not in B lymphocytes. This reactivity was upregulated by IL-7 in a dose dependent manner. Lipopolysaccharide (LPS) treatment induced the upregulation of CD40, CD80, CD86 and the T-cell stimulatory capacity in IL-4-DCs and, to a lesser extent, in the IL-7-DCs whereas GM-CSF-DCs responded very poorly to such treatment. Our data indicate that, together with GM-CSF, the IL-7 drives macrophage precursors to a differentiation stage that is close to but distinct from the phenotype of IL-4-DCs. Comparison of DC development in the presence of IL-7 or IL-4 may help in dissecting signalling pathways that regulate the expression of functionally relevant DC markers.