Figure 1.

Expression of melanocortin receptor (MC-R) -specific messenger RNA by human monocytes and dendritic cells (DCs). Total RNA was obtained from CD14⁺ monocytes before and after they had been differentiated in vitro to DCs. The DCs were treated with lipopolysaccharide (LPS; 1 μg/ml) for 40 hrs to generate mature DCs. Transcript levels for the five known MC-Rs were determined by reverse transcription–polymerase chain reaction using oligonucleotides specific for each receptor. The reverse transcriptase-negative samples are included to control for DNA contamination. (a) CD14⁺ monocytes express messenger RNA for MC-1R whereas (b) DCs express MC-1R as well as the other four known MC-Rs. GAPDH (bottom) was used as a loading control. Abbreviations used: iDC, immature DCs; LPS-DC; mature DCs; negative control: dH₂O; positive control: complementary DNA from cell lines WM266.4 or A375-SM.