D. Longoni et al., INTERLEUKIN-10 INCREASES MANNOSE RECEPTOR EXPRESSION AND ENDOCYTIC ACTIVITY IN MONOCYTE-DERIVED DENDRITIC CELLS, International journal of clinical & laboratory research, 28(3), 1998, pp. 162-169
Human monocyte-derived dendritic cells were differentiated in vitro fo
r 7 days with granulocyte macrophage-colony stimulating factor and int
erleukin-13. These cultured dendritic cells are at an immature stage o
f differentiation and exhert high endocytic activity via surface manno
se receptor and via fluid-phase macropinocytosis. We have investigated
the modulation of endocytosis by interleukin-10 in these cells. When
added during the last 24 h of the 7-day culture, interleukin-10 signif
icantly stimulated the uptake of fluorescein-labelled dextran (39 +/-
16% increase, mean +/-SD of 6 experiments), a sugar binding to the man
nose receptor. This effect was dose dependent and correlated with the
length of exposure to interleukin-10, with a maximal effect (more than
seven-fold increase) when the cytokine was added at the beginning of
the culture (day 0). The interleukin-10-increased fluorescein-labelled
-dextran endocytosis was mostly mediated via the mannose receptor, as
unlabelled mannose and specific antimannose receptor monoclonal antibo
dy inhibited most of the uptake. Moreover, interleukin-10-treated cell
s expressed increased levels (up to four-fold) of mannose receptor. In
terleukin-10 also increased, although to a lesser extent, the fluid-ph
ase endocytosis (macropinocytosis) of fluorescein-labelled albumin. In
terleukin-10 had the opposite effect on the differentiation and functi
onal activity of monocyte-derived dendritic cells; cells having a very
low stimulatory capacity and reduced expression of MHC class II and C
D1a after a 7-day exposure. Thus interleukin-10 had a strong immunosup
pressive effect on the differentiation and functional activity of mono
cyte-derived dendritic cells and yet strongly stimulated endocytosis i
n these cells. We speculate that an increased endocytic activity would
eventually result in a decreased availability of antigens in the exte
rnal milieu, thus contributing to the immunosuppressive and tolerogeni
c activity of interleukin-10.