Soluble CD83 inhibits human monocyte differentiation into dendritic cells in vitro

Human CD83 is type I transmembrane glycoprotein, mainly expressed on mature dendritic cells (DCs), so it was first described as a molecular marker for mature DC. However, increasing evidence has demonstrated that CD83 is also an immunomodulatory molecule either its membrane-bound CD83 (mCD83) or soluble CD83 (sCD83) released from DCs. Intriguingly, the mCD83 possesses stimulatory effects on immune response, on the contrary, the sCD83 has inhibitory effects. Whether the sCD83 has the inhibitory effects on human monocyte differentiation into DCs is unknown. To this end, we prepared the recombinant human sCD83 in HEK293T cells and treated human monocytes being differentiated into DCs in vitro with the sCD83, and evaluate sCD83 inhibitory effects on immune response by analyzing the surface marker pattern of the cells. The results showed that the sCD83, especially glycosylated sCD83 could bind the monocytes and significantly inhibited the depression of CD14 expressions (P < 0.01) and reduced CD1a, CD80, CD86 and MHC II expressions (P < 0.01 or P < 0.05) during the differentiation, indicating that the sCD83 can inhibit monocyte differentiation into DCs, and suggesting that a negative feedback regulation may exist in monocyte differentiation into DCs based on sCD83 released from the mature DCs.