Human dendritic cells contain cell surface sialyltransferase activity.

Area of Science:

• Immunology
• Cell Biology
• Glycobiology

Background:

• Human monocyte-derived dendritic cells (mo-DCs) exhibit extensive cell surface sialylation.
• The precise function of mo-DC sialylation in maturation, immunogenicity, and endocytosis remains incompletely understood.
• Previous studies indicated that mo-DC surface sialylation can be modulated by various stimuli.

Purpose of the Study:

• To investigate the hypothesis that cell surface sialyltransferases exist on mo-DCs.
• To determine if these enzymes can rapidly alter mo-DC surface sialylation and modulate cellular functions.
• To explore the functional consequences of ecto-sialyltransferase activity on mo-DC endocytosis and maturation.

Main Methods:

• Assessing sialic acid incorporation into mo-DC surfaces using exogenous CMP-Neu5Ac.
• Utilizing specific inhibition assays to confirm genuine sialyltransferase activity.
• Evaluating the impact of ecto-sialyltransferase activity on mo-DC endocytic capacity and maturation state.

Main Results:

• Mo-DCs incorporate significant amounts of sialic acids onto their cell surface, particularly after desialylation or maturation.
• This incorporation represents genuine ecto-sialyltransferase activity, independent of secreted enzymes.
• Ecto-sialyltransferase activity leads to a marked decrease in mo-DC endocytic capacity without altering maturation.

Conclusions:

• Ecto-sialyltransferases play a dynamic role in controlling mo-DC sialylation.
• This activity has functional implications, notably down-regulating endocytosis.
• The findings suggest a potential role in physiological and pathological conditions like inflammation and infection for immune regulation.