Human γδ T Cells Induce Dendritic Cell Maturation

γδ T cells are known to be involved in the innate immune defenses against infectious microorganisms. Herein, we considered that γδ T cells could also influence adaptative immunity by interacting with dendritic cells (DC) in the early phase of the immune response. To investigate this hypothesis, γδ T cells isolated from the peripheral blood of healthy volunteers were cocultured with autologous monocyte-derived dendritic cells, which were subsequently analyzed for their expression of key surface molecules and for their production of IL-12. First, we found that γδ T cells induced the upregulation of HLA-DR, CD86, and CD83 on DC. This effect did not require cell to cell contact and could be blocked by a neutralizing anti-TNF antibody. We then observed that γδT cells activated by the synthetic phosphoantigen bromohydrin pyrophosphate (BrHPP) induced the production of IL-12 (p40) and IL-12 (p70) by DC, an effect that involved IFN-γ production. The relevance of this finding to DC function was demonstrated by the increased production of IFN-γ by alloreactive T cells when stimulated in a mixed leucocyte reaction with DC preincubated with activated γδ T cells. We conclude that γδ T cell activation might result in DC maturation and thereby in enhanced αβ T cell responses.