The activation of macrophages, dendritic cells and other APCs depends on antigen binding to membrane surface receptors followed by internalization, intracellular processing and presentation. Several recent studies have focused on antigen targeting to APCs1, 2, 3. Two different approaches have been explored. In one approach, specific ligand-receptor pairs such as gp96-CD913 and OmpA-TLR21 were used for antigen targeting. In another approach, selective stimulation with soluble factors was used: monocytes were targeted by switching-on IL-6−dependent differentiation into macrophages2. The latter strategy seems to recapitulate steps that occur when monocytes cross the vascular endothelium. These findings suggest that it is possible to target APCs as a strategy for augmenting or suppressing the immune response.