5-HT modulates the properties of dendritic cells to interfere with the development of type 1 regulating T cells.

Background: 5-hydroxytryptamine (5-HT, serotonin) is a major mediator in allergic reactions. The number of tolerogenic dendritic cell (tolDC) and regulatory T cell is reduced in allergic disorders. The mechanism is unclear. The objective of this study is to elucidate the role of 5-HT in interfering with tolDC generation and regulatory Type 1 T cell (Tr1 cell).

Methods: BALB/c mice were treated with 5-HT-containing nasal instillations. The frequency of tolDC and Tr1 cell was evaluated by flow cytometry.

Results: Following treatment with 5-HT nasal instillations for one week, the frequency of tolDC and Tr1 cell was significantly reduced in the respiratory tissues. Higher levels of SOS1 were detected in DCs isolated from the airway tissues of mice treated with 5-HT. A complex of SOS1 and c-Maf was detected in DCs in response to 5-HT stimulation. The expression of IL-10 was suppressed by the presence of 5-HT. The induction of Tr1 cell by DC was substantially compromised by 5-HT.

Conclusions: 5-HT inhibits the expression of IL-10 in DCs. DCs primed with 5-HT lose the ability to induce Tr1 cells.