CpG oligodeoxynucleotides enhance FccRI-mediated cross presentation by dendritic cells

Dendritic cells (DC) can trigger naive CD8 T cell responses by their capacity to cross-present exogenous antigens via the major histocompatibility complex class I pathway. The myeloid class I IgG receptor, FccRI (CD64), is expressed on DC, and in vivo targeting of antigens to FccRI induces strong humoral and cellular immune responses. We studied the capacity of human FccRI (hFccRI) to facilitate DC-mediated cross presentation and T cell activation, and assessed the effect of CpG oligodeoxynucleotides on this process. We generated hFccRI expressing immature DC from hFccRI transgenic and immature DC from non-transgenic mice. Antigens were targeted to Fcc receptors as ovalbumin immune complexes, or selectively to hFccRI via ovalbumin–CD64 mAb fusion proteins. Coincubation of immature DC with CpG ODN led to markedly increased MHC class I presentation of FccR-targeted antigens. When OVA was selectively targeted to hFccRI, few differences were observed between Tg and NTg DC. However, upon co-incubation with CpG ODN, hFccRI-triggered cross presentation was enhanced. These results document the capacity of hFccRI on DC to trigger cross presentation via MHC class I upon co-culture with CpG ODN.