Figure 6.

[Nle⁴, DPhe⁷]-α-melanocyte-stimulating hormone (NDP-MSH) impairs the ability of dendritic cells (DCs) to stimulate allogeneic T-cell proliferation even upon removal of NDP-MSH from the medium. CD14⁺-enriched cells were cultured in granulocyte–macrophage colony-stimulating factor and interleukin-4 for 6 days to generate DCs either in the absence or presence of NDP-MSH. Mature DCs were produced by stimulating DCs with lipopolysaccharide (1 μg/ml) for 40 hr. Allogeneic T cells were then stimulated for 5 days with titrated numbers of DCs in 96-well plates in (a) the absence or (b) the presence of NDP-MSH according to the Materials and methods section. Cell proliferation was evaluated after pulsing with [³H]thymidine at 1 μCi/well and is expressed as the mean counts per minute (c.p.m.) of triplicate wells. Error bars represent standard deviations. Thymidine uptake by DCs and T cells alone was subtracted as background. Analysed by Student’s t test: *P < 0·005, **P < 0·0005 indicated for mature DCs versus mature DCs treated with NDP-MSH. Results are representative of six separate experiments.