Inefficient antigen presentation via the IgA Fc receptor (FcαRI) on dendritic cells

Dendritic cells (DC) are professional antigen presenting cells that can induce and regulate adaptive immune responses. For that reason, DC are attractive candidates for vaccination strategies. Recently, expression of the IgA Fc receptor (FcαRI, CD89) was observed on DC, which activation led to DC maturation. We have investigated the potential of DC FcαRI as a target molecule for vaccination against cancer. FcαRI expression was observed on human blood myeloid DC. Furthermore, expression of FcαRI was low on immature DC, cultured from either human monocytes or FcαRI transgenic (Tg) mouse bone marrow cells. Addition of TNF-α to culture regimes of both human and mouse DC led to more semi-mature DC, on which FcαRI expression was slightly upregulated. FcαRI on both human and FcαRI Tg mouse DC was internalized after receptor crosslinking. Antigen presentation, measured in FcαRI Tg mouse DC, was however minimal. As antigen presentation is crucial to elicit effective T cell responses, these data suggest that targeting of DC FcαRI is not optimal for DC vaccination strategies.