Two members of the ADAM (a
disintegrin and
metalloprotease)-family, MADDAM and
decysin, were described as dendritic cell (DC) maturation markers. We are interested in monocyte differentiation and investigated in particular the expression pattern of both genes during the differentiation of human monocytes into DC and macrophages (MAC). Both genes are weakly expressed in freshly isolated monocytes. In immature DC
decysin mRNA was absent, even after induction of the terminal differentiation of DC by
CD40L or tumour
necrosis factor-alpha (
TNF-alpha). Only in DC maturated by
lipopolysaccharide (LPS) strong signals of
decysin mRNA were detected. However, MADDAM
mRNA was expressed in immature DC and the expression was markedly increased after induction of the terminal DC differentiation by various stimuli. In contrast, MAC showed a high constitutive
decysin mRNA expression, but expressed no MADDAM
mRNA. On
protein level similar results of MADDAM expression were obtained. Stimulation of MAC by LPS did not induce MADDAM
mRNA expression, while
decysin mRNA expression was strongly increased. Further investigations revealed that the well-known inducer of MAC differentiation, 1alpha,25-dihydroxyvitamin D3 up-regulated
decysin mRNA expression during the differentiation of primary monocytes and myelomonocytic THP-1 cells into MAC. In vivo
decysin mRNA expression was only detected in human colon, but not in other tissues we examined. Accordingly, isolated intestinal MAC expressed
decysin mRNA. In conclusion,
decysin and MADDAM
mRNA expression were regulated in an opposite way during monocyte differentiation: MADDAM
mRNA and
protein was mainly detected in DC, whereas
decysin mRNA expression was mainly found in MAC. Therefore only MADDAM, but not
decysin is a suitable marker for human monocyte-derived DC.